Humidity
- The drier the air around the leaf, the faster transpiration happens
- If the air around the leaf is humid then there's lots of water in it already so theres not much diffusion taking place as there isn't a massive concentration difference
Wind speed
- The higher the windspeed, the greater the transpiration
- If windspeed around the leaf is slow, water vapour will not move away from the leaf. This means there is a high concentration of water particles inside and outside the leaf so diffusion is very slow.
- If it is windy the water vapour surrounding the leaf its swept away, meaning a low concentration of water outside the leaf. Diffusion will happen quickly, as there is an area of low concentration (outside) and an area of high concentration (inside the leaf).
Temperature
- The warmer it is, the faster transpiration happens. This is because, when it is warmer, the water particles have more energy to evaporate and diffuse out of the stomata
Light intensity
- The brighter the light, the greater the transpiration rate. This is because stomata close when it is dark (as photosynthesis can't occur, so there is no need to let in CO2). When stomata are closed, very little transpiration can occur.
Monday 28 March 2016
2.54 understand that transpiration is the evaporation of water from the surface of a plant
Transpiration is the loss of water from a plant. It is caused by evaporation and diffusion of water from a plants surface (this mostly happens in the leaves).
2.53 explain how water is absorbed by root hair cells
Cells in the roots of plants grow hairs which stick out into the soil taking in water. Each branch of a root will be covered in millions of these cells, this gives the plant a big surface area for absorbing water. There is (usually) a higher concentration of water in the soil than there is inside the plant, so water is drawn into the root hair cell by active transport.
NOTE: It doesn't say anywhere in the spec that we need to be able to draw a root hair cell but it did come up in my mock in January so here's a diagram just incase (:
NOTE: It doesn't say anywhere in the spec that we need to be able to draw a root hair cell but it did come up in my mock in January so here's a diagram just incase (:
2.52 describe the role of xylem in transporting water and mineral salts from the roots to other parts of the plant
Xylem tubes transport water and minerals from the roots into the leaves in the transpiration stream (via the stem/shoot).
2.51 describe the role of the phloem in transporting sucrose and amino acids between the leaves and other parts of the plant
Phloem tubes transport sugars and amino acids from the leaf to the other parts of the plant (this is known as translocation).
2.50 understand the need for a transport system in multicellular organisms
In multicellular organisms, direct diffusion from the outside/outer surface would be too slow because substances would have to travel large distances to reach every cell. A transportation system ensures substances move quickly and efficiently to and from individual cells.
2.49 understand why simple, unicellular organisms can rely on diffusion for movement of substances in and out of the cell
In unicellular organisms, the substances they need to live (for example, water, minerals, sugars perhaps) can diffuse directly in and out of the cell (across the cell membrane). Because of the short distance, the diffusion is quick and efficient so there is no need for a transportation system to move substances quickly.
2.48 describe experiments to investigate the effect of exercise on breathing in humans
Method
- Sit as still as possible for 5 minutes
- Time 1 minute and count the number of breaths you take
- Do 5 minutes of exercise
- Immediately after, time 1 minute and count the number of breaths you take
- Repeat experiment 3 times to ensure an accurate result (and remove any anomalies).
Conclusion
If all goes well, your results should show that exercise increases heart rate (increased breaths = increased heart rate)
NOTE: during the experiment you will need to control all things that could affect your results. E.g level of exercise, time spent exercising, temperature in room/test area, size of person etc
- Sit as still as possible for 5 minutes
- Time 1 minute and count the number of breaths you take
- Do 5 minutes of exercise
- Immediately after, time 1 minute and count the number of breaths you take
- Repeat experiment 3 times to ensure an accurate result (and remove any anomalies).
Conclusion
If all goes well, your results should show that exercise increases heart rate (increased breaths = increased heart rate)
NOTE: during the experiment you will need to control all things that could affect your results. E.g level of exercise, time spent exercising, temperature in room/test area, size of person etc
2.47 understand the biological consequences of smoking in relation to the lungs and the circulatory system, including coronary heart disease
Smoking can damage the walls of the alveoli which will reduce the surface area of the lungs. This will reduce the surface area for gas exchange and lead to diseases such as emphysema.
Cilia (the hairs that line the trachea and lungs) catch dust and bacteria before they reach the lungs. However, they can be damaged by the tar in cigarettes, which leads to an increased possibility of chest infections (as lots of dust and bacteria can enter).
As well as damaging cilia, tar irritates bronchi and bronchioles. This encourages mucus to be produced which can not be cleared if the cilia is damaged. This leads to smokers cough and chromic bronchitis.
Carbon monoxide in cigarette smoke reduces the amount of oxygen the blood can carry by binding with Haemoglobin. To ensure enough oxygen gets to the cells in your body, the heart rate must increase - this can lead to an increase in blood pressure, which will damage artery walls, this makes blood clots much more likely, increasing the chance of coronary heart disease.
Coronary heart disease is caused by a blockage of the coronary arteries that supply heart muscle with blood. If you have coronary heart disease, glucose and oxygen is not transported to the heart muscle (as there is a blockage), therefore the heart can't keep contracting (as it has no glucose/oxygen, so no energy). This will lead to heart attack.
Tobacco smoke contains carcinogens - these are chemicals that can lead to cancer.
Cilia (the hairs that line the trachea and lungs) catch dust and bacteria before they reach the lungs. However, they can be damaged by the tar in cigarettes, which leads to an increased possibility of chest infections (as lots of dust and bacteria can enter).
As well as damaging cilia, tar irritates bronchi and bronchioles. This encourages mucus to be produced which can not be cleared if the cilia is damaged. This leads to smokers cough and chromic bronchitis.
Carbon monoxide in cigarette smoke reduces the amount of oxygen the blood can carry by binding with Haemoglobin. To ensure enough oxygen gets to the cells in your body, the heart rate must increase - this can lead to an increase in blood pressure, which will damage artery walls, this makes blood clots much more likely, increasing the chance of coronary heart disease.
Coronary heart disease is caused by a blockage of the coronary arteries that supply heart muscle with blood. If you have coronary heart disease, glucose and oxygen is not transported to the heart muscle (as there is a blockage), therefore the heart can't keep contracting (as it has no glucose/oxygen, so no energy). This will lead to heart attack.
Tobacco smoke contains carcinogens - these are chemicals that can lead to cancer.
2.46 explain how alveoli are adapted for gas exchange by diffusion between air in the lungs and blood in capillaries
NOTE: we need to know like how alveoli does the gas exchange and stuff but i can't really find it in the spec so I'm just going to put it here in red (if you already know it, skip past the red)
Okay so the lungs contain millions and millions of alveoli. The blood passing next to the alveoli has just returned back to the lungs (from going around the body). This blood contains lots of CO2 and little O2. Oxygen (from the air you've just breathed in) diffuses out the alveolus into the blood (from a high concentration, in the alveolus, to a low concentration, in the blood). CO2 diffuses out of the blood (high concentration) into the alveolus (low concentration) to be breathed out.
How are alveoli specialised for gas exchange...
- Millions of them (gives a really big surface area)
- Moist lining for O2 and CO2 to dissolve in
- The alveoli walls are only 1 cell thick (which is very thin) - meaning the gas doesn't have far to diffuse
- Their walls are permeable - meaning O2 and CO2 can easily diffuse across them
Okay so the lungs contain millions and millions of alveoli. The blood passing next to the alveoli has just returned back to the lungs (from going around the body). This blood contains lots of CO2 and little O2. Oxygen (from the air you've just breathed in) diffuses out the alveolus into the blood (from a high concentration, in the alveolus, to a low concentration, in the blood). CO2 diffuses out of the blood (high concentration) into the alveolus (low concentration) to be breathed out.
How are alveoli specialised for gas exchange...
- Millions of them (gives a really big surface area)
- Moist lining for O2 and CO2 to dissolve in
- The alveoli walls are only 1 cell thick (which is very thin) - meaning the gas doesn't have far to diffuse
- Their walls are permeable - meaning O2 and CO2 can easily diffuse across them
2.45 understand the role of the intercostal muscles and the diaphragm in ventilation
Ventilation is the fancy name for breathing in and out.
Breathing in...
- Intercostal muscles contact (pulling ribcage and sternum 'up and out')
- diaphragm contracts (pulling the thorax 'down')
- Volume of thorax increases
- Pressure inside thorax decreases - this draws air in
Breathing out...
- Intercostal muscles and diaphragm relax
- Thorax volume decreases
- Air is forced out (as the volume decreases and pressure increases)
Breathing in...
- Intercostal muscles contact (pulling ribcage and sternum 'up and out')
- diaphragm contracts (pulling the thorax 'down')
- Volume of thorax increases
- Pressure inside thorax decreases - this draws air in
Breathing out...
- Intercostal muscles and diaphragm relax
- Thorax volume decreases
- Air is forced out (as the volume decreases and pressure increases)
2.44 describe the structure of the thorax, including the ribs, intercostal muscles, diaphragm, trachea, bronchi, bronchioles, alveoli, and pleural membranes
The thorax is basically just the top part of your body, kind of...
When you breathe in, air goes into the trachea (the trachea is just your windpipe). It splits into two tubes called the bronchi, one bronchus goes into each lung. Cartilage supports the airways and keep them open (for breathing).
The bronchi split into smaller and smaller tubes, known as bronchioles.
The bronchioles end at a 'bag' called alveoli (this is where gas exchange takes place)
Pleural membrane surrounds the lungs, protecting them (along with the ribs. It is a continuous envelope around lungs, forming airtight seal.
The diaphragm separates the thorax from the lower half of the body
Image source: igcse-biology
When you breathe in, air goes into the trachea (the trachea is just your windpipe). It splits into two tubes called the bronchi, one bronchus goes into each lung. Cartilage supports the airways and keep them open (for breathing).
The bronchi split into smaller and smaller tubes, known as bronchioles.
The bronchioles end at a 'bag' called alveoli (this is where gas exchange takes place)
Pleural membrane surrounds the lungs, protecting them (along with the ribs. It is a continuous envelope around lungs, forming airtight seal.
The spaces between the two pleural membranes are called the pleural cavity. The pleural cavity filled with layer of liquid called pleural liquid which lubrication so lungs do not stick onto chest wall during breathing.
Ribs Protect the lungs (they are always the light coloured one and first one)
Intercostal muscles join ribs together. They contract and relax as air moves in and out of the lungs.
Intercostal muscles join ribs together. They contract and relax as air moves in and out of the lungs.
The diaphragm separates the thorax from the lower half of the body
Image source: igcse-biology
2.43 describe experiments to investigate the effect of light on net gas exchange from a leaf, using hydrogen-carbonate indicator
Hydrogen-carbonate indicator changes colour with different levels of CO2. In little CO2, it goes purple, in normal CO2, it's orange and in lots of CO2, it goes yellow. We need to know an experiment to show how light effects gas exchange, heres how its done...
Method
- Add the same volume pf hydrogen-carbonate indicator to four test tubes.
- Put a similar sized (healthy) leaf in 3 of the tubes and seal all four with a bung - trap the leaf stem in the bung to ensure it doesn't fall in the indicator. NOTE: the empty test tube is a control.
- Wrap one tube in aluminium foil (this ensures no light will get to that leaf - meaning photosynthesis can't occur)
- Wrap one tube in gauze (this means it has some light, but not full light - slowing the rate of photosynthesis)
- Place all four tubes in bright light
- Leave tubes for 1 hour
- Record the colour of the indicator
Conclusion
If all went well, there shouldn't be any colour change in the control tube, as no photosynthesis (so no gas exchange) occurred there. In the tube with aluminium foil around it, the hydrogen-carbonate indicator will be dark yellow. This is because it was not able to photosynthesise but respiration still took place, meaning the CO2 level in the tube will increase (as CO2 has been given out by respiration, but not taken in by photosynthesis). There will be no change as a little photosynthesis and respiration have taken place, so the CO2 level won't have changed much. The tube with access to full light will have gone purple. This is because the level of CO2 would have decreased as there will be some respiration, but lots of photosynthesis, meaning lots of CO2 was taken in by the leaf (but not much given out).
Method
- Add the same volume pf hydrogen-carbonate indicator to four test tubes.
- Put a similar sized (healthy) leaf in 3 of the tubes and seal all four with a bung - trap the leaf stem in the bung to ensure it doesn't fall in the indicator. NOTE: the empty test tube is a control.
- Wrap one tube in aluminium foil (this ensures no light will get to that leaf - meaning photosynthesis can't occur)
- Wrap one tube in gauze (this means it has some light, but not full light - slowing the rate of photosynthesis)
- Place all four tubes in bright light
- Leave tubes for 1 hour
- Record the colour of the indicator
Conclusion
If all went well, there shouldn't be any colour change in the control tube, as no photosynthesis (so no gas exchange) occurred there. In the tube with aluminium foil around it, the hydrogen-carbonate indicator will be dark yellow. This is because it was not able to photosynthesise but respiration still took place, meaning the CO2 level in the tube will increase (as CO2 has been given out by respiration, but not taken in by photosynthesis). There will be no change as a little photosynthesis and respiration have taken place, so the CO2 level won't have changed much. The tube with access to full light will have gone purple. This is because the level of CO2 would have decreased as there will be some respiration, but lots of photosynthesis, meaning lots of CO2 was taken in by the leaf (but not much given out).
2.42 describe the role of stomata in gas exchange
Guard cells control the opening and closing of stomata. During daytime (when photosynthesis occurs) stomata are open allowing for CO2 and O2 to enter (by diffusion). At night time, the stomata close. This is because photosynthesis doesn't occur so there is no need to have stomata open all the time (as no CO2 needs to be taken into the leaf). However, during the night stomata may open periodically to allow oxygen to diffuse in for respiration of cells.
2.41 explain how the structure of the leaf is adapted for gas exchange
The leaf is adapted for gas exchange in many ways, here are a few...
- It is thin, meaning gases only have to travel a short distance (to reach the cells where they are needed)
- They are broad, meaning there's a large surface area for diffusion
- Air spaces inside the leaf let CO2 and O2 move easily between cells (they also increase the surface area for gas exchange)
- Stomata let CO2 and O2 diffuse - they also allow water to escape (transpiration)
- Stomata close when its dark as photosynthesis doesn't occur in the dark so there is no need for stomata to let in CO2. When stomata are closed no water can escape - this stops the plant drying out.
NOTE: the opening and closing of stomata is controlled by guard cells
- It is thin, meaning gases only have to travel a short distance (to reach the cells where they are needed)
- They are broad, meaning there's a large surface area for diffusion
- Air spaces inside the leaf let CO2 and O2 move easily between cells (they also increase the surface area for gas exchange)
- Stomata let CO2 and O2 diffuse - they also allow water to escape (transpiration)
- Stomata close when its dark as photosynthesis doesn't occur in the dark so there is no need for stomata to let in CO2. When stomata are closed no water can escape - this stops the plant drying out.
NOTE: the opening and closing of stomata is controlled by guard cells
2.40 understand that respiration continues during the day and night, but that the net exchange of carbon dioxide and oxygen depends on the intensity of light
Photosynthesis happens when light is available (as it takes energy from the light source). However, plants must respire all the time, else they would die. In the day (when light intensity is strong) plants make more O2 from photosynthesis than they use in respiration, so in daytime they release this O2 (by diffusion), they also use up more CO2 than they produce, so they take in CO2 (by diffusion). At nighttime (when light intensity is low) plants only respire. This is because there is not enough light for photosynthesis (this means they take in oxygen and release CO2).
2.39 understand gas exchange (of carbon dioxide and oxygen) in relation to respiration and photosynthesis
During respiration - plants use up oxygen and produce CO2 (as a waste product).
During photosynthesis - plants use up CO2 and produce O2 (as a waste product). As CO2 is being used up, it diffuses from outside the leaf into the leaf.
During photosynthesis - plants use up CO2 and produce O2 (as a waste product). As CO2 is being used up, it diffuses from outside the leaf into the leaf.
2.38 understand the role of diffusion in gas exchange
When plants photosynthesise, they use up CO2 and produce O2. When plants respire, they use up O2 and produce CO2. This means there is a lot of gas exchange in plants, this happens by diffusion.
When a plant is photosynthesising it uses up CO2 (so there is barely any left in the leaf). This causes more CO2 to enter the leaf (by diffusion) - from an area of high concentration (outside the leaf) to an area of low concentration (inside the leaf). At the same time, O2 is being produced (as a waste product of photosynthesis), some of this is used for respiration whilst the rest diffuses out of the leaf (through the stomata) - moving from an area of high concentration (in the leaf) to an area of low concentration (outside the leaf).
When a plant is photosynthesising it uses up CO2 (so there is barely any left in the leaf). This causes more CO2 to enter the leaf (by diffusion) - from an area of high concentration (outside the leaf) to an area of low concentration (inside the leaf). At the same time, O2 is being produced (as a waste product of photosynthesis), some of this is used for respiration whilst the rest diffuses out of the leaf (through the stomata) - moving from an area of high concentration (in the leaf) to an area of low concentration (outside the leaf).
2.37 describe experiments to investigate the evolution of carbon dioxide and heat from respiring seeds or other suitable living organisms
Carbon dioxide
Carbon dioxide can be tested using an indicator. Here's how its done...
- Soak some dried beans in water for a day (to start the germination process, as germinating beans will respire)
- Boil the same amount of beans (that are similar sized). This will kill the beans, ensuring they can not respire
- Put hydrogen-carbonate indicator in two test tubes
- Place a platform made of gauze into each test tube and place the beans on this platform
- Seal the test tubes with a bung (to ensure no gas escapes)
- Leave the apparatus for 1 hour (or a set length of time)
Conclusion - if all goes well, the hydrogen-carbonate indicator in the germinating seeds test tube should have gone yellow (as the seeds produced CO2) whereas there should be no change to the dead seed test tube.
NOTE: the dead beans will act as a control
Heat
Respiration gives of heat. Heres how to measure it...
- Soak some dried beans in water for a day (to start the germination process, as germinating beans will respire)
- Boil the same amount of beans (that are similar sized). This will kill the beans, ensuring they can not respire
- Add each set of beans to a vacuum flask. Ensure there is air in the flask so the beans can respire aerobically
- Place a thermometer into each flask and seal the top with cotton wool
- Record the temperature of each flask everyday for 1 week
Conclusion - if all goes well, the germinating beans respire and produce heat, therefore, the temperature of the germinating flask will increase compared to the temperature of the dead flask.
NOTE: the dead beans flask is the control flask
Carbon dioxide can be tested using an indicator. Here's how its done...
- Soak some dried beans in water for a day (to start the germination process, as germinating beans will respire)
- Boil the same amount of beans (that are similar sized). This will kill the beans, ensuring they can not respire
- Put hydrogen-carbonate indicator in two test tubes
- Place a platform made of gauze into each test tube and place the beans on this platform
- Seal the test tubes with a bung (to ensure no gas escapes)
- Leave the apparatus for 1 hour (or a set length of time)
Conclusion - if all goes well, the hydrogen-carbonate indicator in the germinating seeds test tube should have gone yellow (as the seeds produced CO2) whereas there should be no change to the dead seed test tube.
NOTE: the dead beans will act as a control
Heat
Respiration gives of heat. Heres how to measure it...
- Soak some dried beans in water for a day (to start the germination process, as germinating beans will respire)
- Boil the same amount of beans (that are similar sized). This will kill the beans, ensuring they can not respire
- Add each set of beans to a vacuum flask. Ensure there is air in the flask so the beans can respire aerobically
- Place a thermometer into each flask and seal the top with cotton wool
- Record the temperature of each flask everyday for 1 week
Conclusion - if all goes well, the germinating beans respire and produce heat, therefore, the temperature of the germinating flask will increase compared to the temperature of the dead flask.
NOTE: the dead beans flask is the control flask
Friday 25 March 2016
2.36 write the word equation for anaerobic respiration in plants and in animals
Animals
glucose ---> lactic acid (+ energy)
Plants
glucose ---> ethanol + carbon dioxide (+ energy)
glucose ---> lactic acid (+ energy)
Plants
glucose ---> ethanol + carbon dioxide (+ energy)
2.35 write the word equation and the balanced chemical symbol equation for aerobic respiration in living organisms
Glucose + oxygen ---> carbon dioxide + water (+ energy)
C6H12O6 + 6O2 → 6CO2 + 6H2O (+ energy)
C6H12O6 + 6O2 → 6CO2 + 6H2O (+ energy)
2.34 describe the differences between aerobic and anaerobic respiration
Aerobic respiration occurs when oxygen is present, it is the most efficient way to release energy from glucose and is the respiration humans use most of the time.
Anaerobic respiration in animals occurs when there is no oxygen present, for example, when you do lots of exercise. When you do lots of exercise your body can't supply enough oxygen to your muscles for aerobic respiration, therefore, your muscles must anaerobically respire.
Anaerobic respiration releases less energy than aerobic respiration and therefore it is not the best way to convert glucose into energy. In anaerobic respiration, glucose is only partially broken down (this produces lactic acid)
This lactic acid builds up in muscles and gets very painful (sometimes leads to cramp)
Anaerobic respiration in plants is the same as animals only ethanol and CO2 is produced in place of lactic acid
Anaerobic respiration in plants is the same as animals only ethanol and CO2 is produced in place of lactic acid
2.33 understand that the process of respiration releases energy in living organisms
Respiration is not breathing in and out, it is the process of releasing energy from glucose and it occurs in every cell. Energy is released as chemical and heat energy. The two types of respiration are aerobic respiration and anaerobic respiration.
The definition needed for exams: respiration is the process of releasing energy from glucose (it occurs in every living cell)
The definition needed for exams: respiration is the process of releasing energy from glucose (it occurs in every living cell)
2.32 describe an experiment to investigate the energy content in a food sample
Calorimetry is basically burning food to obtain its energy content.
Method
- Obtain a food that will burn easily (e.g dry substance, like peanuts)
- Weigh a small sample of the food
- Skewer the sample on a mounted needle
- Add 25cm3 of water to a boiling tube held above the sample (with a clamp) - this will be used to measure the amount of heat energy is released when the food burns
- Measure the temperature of the water, then set fire to the food (using a bunsen burner)
- Hold the food sample directly under the boiling tube until it goes out, then relight it and repeat. Keep repeating until the food will not light anymore
- Measure the temperature of the water again.
NOTE: ensure the bunsen burner is not near the boiling tube, as this may create anomalies
Calculations
STEP 1: To calculate the energy content in Joules, substitute your results into this equation..
energy in food (J) = Mass of water (in g) x temperature change of water (in ºC) x 4.2
NOTE: 1cm3 of water is the same as 1g of water
STEP 2: calculate the amount of energy in Joules per gram
energy per gram of food (in J/g) = energy in food (in J) / mass of food (in g)
Method
- Obtain a food that will burn easily (e.g dry substance, like peanuts)
- Weigh a small sample of the food
- Skewer the sample on a mounted needle
- Add 25cm3 of water to a boiling tube held above the sample (with a clamp) - this will be used to measure the amount of heat energy is released when the food burns
- Measure the temperature of the water, then set fire to the food (using a bunsen burner)
- Hold the food sample directly under the boiling tube until it goes out, then relight it and repeat. Keep repeating until the food will not light anymore
- Measure the temperature of the water again.
NOTE: ensure the bunsen burner is not near the boiling tube, as this may create anomalies
Calculations
STEP 1: To calculate the energy content in Joules, substitute your results into this equation..
energy in food (J) = Mass of water (in g) x temperature change of water (in ºC) x 4.2
NOTE: 1cm3 of water is the same as 1g of water
STEP 2: calculate the amount of energy in Joules per gram
energy per gram of food (in J/g) = energy in food (in J) / mass of food (in g)
Monday 21 March 2016
2.31 describe the structure of a villus and explain how this helps absorption of the products of digestion in the small intestine
The small intestine is adapted for absorption of food as it is very long and also has a large surface area because its walls are covered in tiny projections called villi. Each cell on the surface of a villus also has its own tiny villus, known as micro-villi, these increase he surface area even more.
Villi have a single permeable layer of surface cells and a very good blood supply to assist with quick absorption.
Villi have a single permeable layer of surface cells and a very good blood supply to assist with quick absorption.
2.30 understand that bile is produced in the liver and stored in the gall bladder, and understand the role of bile in neutralising stomach acid and emulsifying lipids
Bile is produced in the liver and is stored in the gall bladder before it's released into the small intestine.
The hydrochloric acid in the stomach makes the pH too acidic (pH2) for enzymes in the small intestine to work properly. However, bile is alkali so it neutralises the acid, making conditions alkaline - this is useful as the enzymes in the small intestine work best in alkaline conditions.
Furthermore, bile also emulsifies lipids (fats). This basically means it breaks down the fat into tiny droplets - this is useful as it gives a much bigger surface area of fat for the enzyme lipase to work on, this makes digestion faster.
The hydrochloric acid in the stomach makes the pH too acidic (pH2) for enzymes in the small intestine to work properly. However, bile is alkali so it neutralises the acid, making conditions alkaline - this is useful as the enzymes in the small intestine work best in alkaline conditions.
Furthermore, bile also emulsifies lipids (fats). This basically means it breaks down the fat into tiny droplets - this is useful as it gives a much bigger surface area of fat for the enzyme lipase to work on, this makes digestion faster.
2.29 understand the role of digestive enzymes, to include the digestion of starch to glucose by amylase and maltase, the digestion of proteins to amino acids by proteases and the digestion of lipids to fatty acids and glycerol by lipase
Starch, proteins and fats are big molecules that are too big to pass through the walls of the digestive system (they're also insoluble). Sugars, amino acids, glycerol and fatty acids are much smaller molecules. They're soluble and can pass easily through the walls of the digestive system.
Digestive enzymes break down the big molecules into the smaller ones.
Starch to glucose by amylase and maltase
- Amylase converts starch into maltose
- Maltase converts maltose into glucose
Proteins to amino acids by proteases
- Proteases convert proteins into amino acids
Digestion of lipids to fatty acids and glycerol by lipases
- Lipases convert lipids into glycerol and fatty acids
Digestive enzymes break down the big molecules into the smaller ones.
Starch to glucose by amylase and maltase
- Amylase converts starch into maltose
- Maltase converts maltose into glucose
Proteins to amino acids by proteases
- Proteases convert proteins into amino acids
Digestion of lipids to fatty acids and glycerol by lipases
- Lipases convert lipids into glycerol and fatty acids
2.28 explain how and why food is moved through the gut by peristalsis
There is muscular tissue that lines the alimentary canal, its job is to squeeze balls of food (known as boluses) through the gut (otherwise it would get stuck). It moves the boluses with squeezing actions which are waves of circular muscle contractions. This is peristalsis.
2.27 understand the process of ingestion, digestion, absorption, assimilation and egestion
The five main stages of digestion are ingestion, digestion, absorption, assimilation and egestion...
Ingestion
This is putting food (or drink) into your mouth (mechanical digestion)
Digestion
Digestion is the break-down of large, insoluble molecules into small, soluble molecules (mechanical digestion)
Absorption
Absorption is the process of moving molecules through the walls of the intestine into the blood. Digested food molecules are absorbed in the small intestine - water is mainly absorbed in the large intestine.
Assimilation
When digested molecules have been absorbed, they're moved into body cells. The digested molecules then become part of the cells (this is assimilation). For example, when amino acids (from digested proteins) are assimilated, they're used by cells to make cellular proteins.
Egestion
All the undigested stuff forms faeces, which are of no use to the body so they are egested through the anus
Ingestion
This is putting food (or drink) into your mouth (mechanical digestion)
Digestion
Digestion is the break-down of large, insoluble molecules into small, soluble molecules (mechanical digestion)
Absorption
Absorption is the process of moving molecules through the walls of the intestine into the blood. Digested food molecules are absorbed in the small intestine - water is mainly absorbed in the large intestine.
Assimilation
When digested molecules have been absorbed, they're moved into body cells. The digested molecules then become part of the cells (this is assimilation). For example, when amino acids (from digested proteins) are assimilated, they're used by cells to make cellular proteins.
Egestion
All the undigested stuff forms faeces, which are of no use to the body so they are egested through the anus
2.26 describe the structures of the human alimentary canal and describe the functions of the mouth, oesophagus, stomach, small intestine, large intestine and pancreas
Okay so the human alimentary canal is just a fancy name for the gut.
Mouth...
- Salivary glands in the mouth produce amylase enzymes (in the saliva)
- Teeth break down food mechanically
Oesophagus...
- This is the muscular tube that connects the mouth and the stomach
Stomach...
- It pummels the food with its muscular wall (mechanical digestion)
- It produces the protease enzyme, pepsin
- It produces hydrochloric acid to kill bacteria and to give the right pH for the protease enzyme to work (pH2)
Pancreas...
- Produces protease, amylase and lipase enzymes. It releases these into the small intestine
Small intestine...
- produces protease, amylase and lipase enzymes to complete digestion
- This is also where the nutrients are absorbed out of the alimentary canal into the body
Large intestine...
- Where excess water is absorbed from the food
Mouth...
- Salivary glands in the mouth produce amylase enzymes (in the saliva)
- Teeth break down food mechanically
Oesophagus...
- This is the muscular tube that connects the mouth and the stomach
Stomach...
- It pummels the food with its muscular wall (mechanical digestion)
- It produces the protease enzyme, pepsin
- It produces hydrochloric acid to kill bacteria and to give the right pH for the protease enzyme to work (pH2)
Pancreas...
- Produces protease, amylase and lipase enzymes. It releases these into the small intestine
Small intestine...
- produces protease, amylase and lipase enzymes to complete digestion
- This is also where the nutrients are absorbed out of the alimentary canal into the body
Large intestine...
- Where excess water is absorbed from the food
2.25 understand that energy requirements vary with activity levels, age and pregnancy
Different 'types' of people require different levels of energy, your energy requirements will depend on...
Your activity level
Active people need more energy than people who sit about all day, as they will be burning much more calories each day and therefore need more energy to burn them
Your age
Children and teenagers will need more energy than adults as they are still growing (and are generally more active)
Pregnancy
Pregnant women need more energy than non-pregnant women as they have to provide energy for not only themselves but also for their babies to develop
Your activity level
Active people need more energy than people who sit about all day, as they will be burning much more calories each day and therefore need more energy to burn them
Your age
Children and teenagers will need more energy than adults as they are still growing (and are generally more active)
Pregnancy
Pregnant women need more energy than non-pregnant women as they have to provide energy for not only themselves but also for their babies to develop
2.24 identify sources and describe functions of carbohydrate, protein, lipid (fats and oils), vitamins A, C and D, and the mineral ions calcium and iron, water and dietary fibre as components of the diet
Carbohydrate - found in pasta, rice, sugar - provides energy
Lipids - found in butter, oily fish - provides energy, acts as an energy store and provides insulation
Proteins - found in meat, fish - needed for growth and repair of tissue, to provide energy in emergencies
Vitamin A - found in liver - helps to improve vision and keep skin and hair healthy
Vitamin C - found in oranges - prevents scurvy
Vitamin D - found in eggs (also made when your skin is exposed to sunlight) - needed for calcium absorption
Mineral ions, calcium - found in milk and cheese - needed to make bones and teeth
Mineral ions, iron - found in red meat - needed to make haemoglobin for healthy blood
Water - found in food and drink - almost every bodily function relies on water. Also, we need a constant supply to replace water lost through urinating, breathing and sweating
Dietary fibre - found in wholemeal foods, such as wholemeal bread - helps peristalsis.
Lipids - found in butter, oily fish - provides energy, acts as an energy store and provides insulation
Proteins - found in meat, fish - needed for growth and repair of tissue, to provide energy in emergencies
Vitamin A - found in liver - helps to improve vision and keep skin and hair healthy
Vitamin C - found in oranges - prevents scurvy
Vitamin D - found in eggs (also made when your skin is exposed to sunlight) - needed for calcium absorption
Mineral ions, calcium - found in milk and cheese - needed to make bones and teeth
Mineral ions, iron - found in red meat - needed to make haemoglobin for healthy blood
Water - found in food and drink - almost every bodily function relies on water. Also, we need a constant supply to replace water lost through urinating, breathing and sweating
Dietary fibre - found in wholemeal foods, such as wholemeal bread - helps peristalsis.
2.23 understand that a balanced diet should include appropriate proportions of carbohydrate, protein, lipids, vitamins, minerals, water and dietary fibre
A balanced diet gives you all the essential nutrients you need, and in the right proportions.
The six essential nutrients are carbohydrates, proteins, lipids, vitamins, minerals and water - dietary fibre is also needed but is not deemed one if 'the six', fibre is used to keep the gut in working well.
The six essential nutrients are carbohydrates, proteins, lipids, vitamins, minerals and water - dietary fibre is also needed but is not deemed one if 'the six', fibre is used to keep the gut in working well.
Sunday 13 March 2016
2.22 describe experiments to investigate photosynthesis, showing the evolution of oxygen from a water plant, the production of starch and the requirements of light, carbon dioxide and chlorophyll
EVOLUTION OF OXYGEN
The best example is using pond weed (Elodea) which produces bubbles of O2 as it photosynthesises.
Method:
- Place 5 sections of Elodea under water in 5 different clear containers (a test tube works best)
- place each test tube at a certain distance from a lamp (for example, at 10cm increments where the first test tube is 10cm away from the lamp, then the 5th is 50cm away)
- Time 1 minute and count the number of bubbles that are produced from each test tube (the bubbles are oxygen, a byproduct of photosynthesis)
Should your experiment go to plan, you should conclude that the test tube closest to the lamp produced the most bubbles due to the fact that the rate of photosynthesis was highest because it was receiving light energy at the highest intensity (the more light energy received, the faster the rate of reaction, and therefore rate of photosynthesis, as the water and carbon dioxide molecules have more energy so they collide quicker/more)
PRODUCTION OF STARCH
A good example of an experiment that proves that light and CO2 are essential for the production of starch is the Geranium plant. It’s leaves normally turn blue-black in the presence of iodine solution showing starch is present (you have to boil it in ethanol first to remove the chlorophyll to show the colour).
However, if one leaf is put in aluminum foil (removing light) and another is kept with lime water (removing CO2) both do not turn blue-black, implying both CO2 and light are essential for starch production and, therefore, essential for photosynthesis.
The best example is using pond weed (Elodea) which produces bubbles of O2 as it photosynthesises.
Method:
- Place 5 sections of Elodea under water in 5 different clear containers (a test tube works best)
- place each test tube at a certain distance from a lamp (for example, at 10cm increments where the first test tube is 10cm away from the lamp, then the 5th is 50cm away)
- Time 1 minute and count the number of bubbles that are produced from each test tube (the bubbles are oxygen, a byproduct of photosynthesis)
Should your experiment go to plan, you should conclude that the test tube closest to the lamp produced the most bubbles due to the fact that the rate of photosynthesis was highest because it was receiving light energy at the highest intensity (the more light energy received, the faster the rate of reaction, and therefore rate of photosynthesis, as the water and carbon dioxide molecules have more energy so they collide quicker/more)
PRODUCTION OF STARCH
A good example of an experiment that proves that light and CO2 are essential for the production of starch is the Geranium plant. It’s leaves normally turn blue-black in the presence of iodine solution showing starch is present (you have to boil it in ethanol first to remove the chlorophyll to show the colour).
However, if one leaf is put in aluminum foil (removing light) and another is kept with lime water (removing CO2) both do not turn blue-black, implying both CO2 and light are essential for starch production and, therefore, essential for photosynthesis.
2.21 understand that plants require mineral ions for growth and that magnesium ions are needed for chlorophyll and nitrate ions are needed for amino acids
In addition to water, sunlight and carbon dioxide, plants also require specific minerals. Different mineral ions do different things, for example...
Nitrate – used to make amino acids for use in plant proteins
Magnesium – forms part of the chlorophyll molecule
Potassium - essential for cell membranes
Phosphate - essential part of DNA and cell membranes
Nitrate – used to make amino acids for use in plant proteins
Magnesium – forms part of the chlorophyll molecule
Potassium - essential for cell membranes
Phosphate - essential part of DNA and cell membranes
2.20 describe the structure of the leaf and explain how it is adapted for photosynthesis
This is the inside of a leaf
2.19 understand how varying carbon dioxide concentration, light intensity and temperature affect the rate of photosynthesis
Carbon dioxide
If there is not enough (insufficient) carbon dioxide, the rate of photosynthesis will decrease. This is because there is less reactant (carbon dioxide), therefore less reaction.
If there is lots of carbon dioxide the rate of photosynthesis will be much higher, as there will be lots of reactant.
Light Intensity
If the light intensity is low the rate of photosynthesis decreases because the energy that the light provides is less, therefore the rate of reaction is decreased.
Alternatively, if the light intensity is high the rate of photosynthesis will increase as the light is providing more energy meaning the rate of reaction will increase.
Temperature
In cold temperatures, the rate of photosynthesis would decrease as the molecules of carbon dioxide and water would have less energy meaning they would collide less (the rate of reaction would be slower).
In hot conditions, the rate of photosynthesis would be faster as molecules would have more energy. However, too high a temperature could have devastating effect. For example, the enzymes could denature/plant could wilt/too much transpiration etc
If there is not enough (insufficient) carbon dioxide, the rate of photosynthesis will decrease. This is because there is less reactant (carbon dioxide), therefore less reaction.
If there is lots of carbon dioxide the rate of photosynthesis will be much higher, as there will be lots of reactant.
Light Intensity
If the light intensity is low the rate of photosynthesis decreases because the energy that the light provides is less, therefore the rate of reaction is decreased.
Alternatively, if the light intensity is high the rate of photosynthesis will increase as the light is providing more energy meaning the rate of reaction will increase.
Temperature
In cold temperatures, the rate of photosynthesis would decrease as the molecules of carbon dioxide and water would have less energy meaning they would collide less (the rate of reaction would be slower).
In hot conditions, the rate of photosynthesis would be faster as molecules would have more energy. However, too high a temperature could have devastating effect. For example, the enzymes could denature/plant could wilt/too much transpiration etc
2.18 write the word equation and the balanced chemical symbol equation for photosynthesis
Word equation:
Carbon dioxide + water glucose + oxygen
glucose + oxygen
Balanced chemical symbol equation:
6CO2 + 6H2O C6H12O6 + 6O2
2.17 describe the process of photosynthesis and understand its importance in the conversion of light energy to chemical energy
Photosynthesis is the process in which plants use energy from the sunlight to convert carbon dioxide and water into molecules needed for growth. It uses light energy (from the sun) to create chemical energy (glucose) - this conserves the energy from the sun. The energy is then passed through the food chain which is why plants are called producers; they produce the chemical energy.
It works like this...
Light energy is absorbed by the green chemical chlorophyll. This energy allows the production of glucose by the reaction between carbon dioxide and water.
A bi-product of photosynthesis is oxygen, which is excreted out of the plant via the stomata.
It works like this...
Light energy is absorbed by the green chemical chlorophyll. This energy allows the production of glucose by the reaction between carbon dioxide and water.
A bi-product of photosynthesis is oxygen, which is excreted out of the plant via the stomata.
2.15 understand the factors that affect the rate of movement of substances into and out of cells, to include the effects of surface area to volume ratio, temperature and concentration gradient
Diffusion and osmosis occur because molecules have kinetic energy. The molecules constantly bounce off each other all the time, gradually spreading out. Eventually there will be an even mixture of molecules, which is called an equilibrium. Diffusion can be affected by;
Changed in kinetic energy
Increased temperature and stirring the medium both increase kinetic energy which will increase the rate of diffusion/osmosis. This is because the molecules will have more energy meaning the molecules will collide with the cell membrane more often making movement through it more likely.
Alternatively, a decrease in temperature will decrease the rate of diffusion/osmosis as it will decrease the amount of kinetic energy in the molecules.
Surface area for diffusion and the surface area to volume ratio
With a larger surface area, molecules have more surface through which to diffuse, this increases the rate of movement which consequently increases the rate of diffusion/osmosis.
The size of the concentration gradient
The concentration gradient is the difference between the concentration inside and outside the cell. The bigger the difference is the more opportunity molecules have of diffusing.
NOTE: The thickness / distance molecules have to diffuse can also affect the rate of movement of substances. For example, diffusion through several cells will take longer than diffusion through a membrane 1 cell thick.
Changed in kinetic energy
Increased temperature and stirring the medium both increase kinetic energy which will increase the rate of diffusion/osmosis. This is because the molecules will have more energy meaning the molecules will collide with the cell membrane more often making movement through it more likely.
Alternatively, a decrease in temperature will decrease the rate of diffusion/osmosis as it will decrease the amount of kinetic energy in the molecules.
Surface area for diffusion and the surface area to volume ratio
With a larger surface area, molecules have more surface through which to diffuse, this increases the rate of movement which consequently increases the rate of diffusion/osmosis.
The size of the concentration gradient
The concentration gradient is the difference between the concentration inside and outside the cell. The bigger the difference is the more opportunity molecules have of diffusing.
NOTE: The thickness / distance molecules have to diffuse can also affect the rate of movement of substances. For example, diffusion through several cells will take longer than diffusion through a membrane 1 cell thick.
2.14 understand the importance in plants of turgid cells as a means of support
A turgid cell is one that is swollen full of water. This is important because they are stronger, therefore they support the plants - meaning the plant will grow upwards. Plant cells have a cell wall to stop them bursting when turgid. When plant cells start to lose water they become flaccid. Flaccid plants lose their strength and start to wilt. Eventually, flaccid cells become plasmolysed as the cell membrane begins to peel away from the cell wall, killing the cell.
This diagram might help for understanding, but it does not need to be learnt.
This diagram might help for understanding, but it does not need to be learnt.
2.13 understand that movement of substances into and out of cells can be by diffusion, osmosis and active transport
Diffusion, osmosis and active transport are the ways in which substances move in/out of cells (through the cell membrane)
2.12 understand definitions of diffusion, osmosis and active transport
Diffusion
The movement of molecules from high concentration to low concentration, down a concentration gradient.
Osmosis
The movement of water molecules from high concentration to low concentration through a partially permeable membrane
Active Transport
The movement of molecules from low concentration to high concentration against the concentration gradient. Energy is required for movement to occur.
2.11 describe experiments to investigate how enzyme activity can be affected by changes in temperature.
NOTE: Amylase is an enzyme which breaks down starch and iodine turns black when starch is present
- Put 30cm^3 of starch in six test tubes
- set up 5 water baths at different temperatures (e.g one at 10º, one at 15º, one at 20º, one at 25º and one at 30º) and put one test tube in each bath until they have all reached the desired temperature (keep one test tube in room temp for a control)
- add 10cm3 of amylase to each test tube (do not put amylase in the control test tube to ensure the starch does not break down without the amylase present)
- add iodine to each tube and time how long it takes for the starch to be digested (iodine will be blue/black with starch and return to normal colour, yellow/orange, once there is no starch present)
- To avoid anomalous results, repeat experiment three times.
Plot a graph of results
- Put 30cm^3 of starch in six test tubes
- set up 5 water baths at different temperatures (e.g one at 10º, one at 15º, one at 20º, one at 25º and one at 30º) and put one test tube in each bath until they have all reached the desired temperature (keep one test tube in room temp for a control)
- add 10cm3 of amylase to each test tube (do not put amylase in the control test tube to ensure the starch does not break down without the amylase present)
- add iodine to each tube and time how long it takes for the starch to be digested (iodine will be blue/black with starch and return to normal colour, yellow/orange, once there is no starch present)
- To avoid anomalous results, repeat experiment three times.
Plot a graph of results
2.10 understand how the functioning of enzymes can be affected by changes in active site caused by changes in pH
As well as temperature, pH levels can also affect enzymes. If the pH gets too high or too low then the bonds holding the enzyme together break, much like a change in temperature. This changes the shape of the active site and consequently means that the enzyme has denatured. This means that the specific substrate can not fit into the active site therefore the enzyme can not break down the substrate.
Much like temperature, all enzymes have an optimum pH as well. This is usually neutral at pH7 but can be different. For example, Pepsin, an enzyme that works in your stomach, has an optimum pH of around 2 (so very acidic).
Much like temperature, all enzymes have an optimum pH as well. This is usually neutral at pH7 but can be different. For example, Pepsin, an enzyme that works in your stomach, has an optimum pH of around 2 (so very acidic).
Saturday 12 March 2016
2.9 understand how the functioning of enzymes can be affected by changes in temperature, including changes due to change in active site
If temperatures are too high the enzyme will denature, meaning that it will not be able to function. This is because the energy breaks the bonds that holds the shape of the enzyme, therefore the active sight is no longer able to bind with the substrate.
However, there is an optimum temperature. This is the temperature that enzymes act best at, it is also just before the temperature at which the enzyme denatures.
The optimum temperature and temperature the enzyme denatures are different for every enzyme.
However, there is an optimum temperature. This is the temperature that enzymes act best at, it is also just before the temperature at which the enzyme denatures.
The optimum temperature and temperature the enzyme denatures are different for every enzyme.
Friday 11 March 2016
2.8 understand the role of enzymes as biological catalysts in metabolic reactions
The most important thing to know about enzymes is that they are chemically unchanged throughout the reaction. Enzymes speed up a reaction by lowering the activation energy of a reaction.
Making a reaction faster and being unchanged are the basic characteristics of a catalyst, therefore, as enzymes speed up reactions and are chemically unchanged throughout the reaction, they are known as biological catalysts.
(for more information on enzymes that is not directly in the spec but may be useful for your understanding : http://www.abpischools.org.uk/page/modules/enzymes/enzymes5.cfm?coSiteNavigation_allTopic=1 )
Making a reaction faster and being unchanged are the basic characteristics of a catalyst, therefore, as enzymes speed up reactions and are chemically unchanged throughout the reaction, they are known as biological catalysts.
(for more information on enzymes that is not directly in the spec but may be useful for your understanding : http://www.abpischools.org.uk/page/modules/enzymes/enzymes5.cfm?coSiteNavigation_allTopic=1 )
2.7 describe the tests for glucose and starch
For these tests, only the observations and chemicals used need to be known, you do not need to worry about anything such as word or symbol equations
Glucose
heat the object you want to test with 'Benedict's' (or 'Fehlings') reagent, if glucose is present the reagent will turn from blue to orange
Starch
Apply iodine (usually with a pipette - although not necessary) to the object you are testing, if it turns from red to blue/black then starch is present (in an exam situation, it is best to write 'blue/black' or 'blue-black' than either 'blue' or 'black')
Glucose
heat the object you want to test with 'Benedict's' (or 'Fehlings') reagent, if glucose is present the reagent will turn from blue to orange
Starch
Apply iodine (usually with a pipette - although not necessary) to the object you are testing, if it turns from red to blue/black then starch is present (in an exam situation, it is best to write 'blue/black' or 'blue-black' than either 'blue' or 'black')
2.6 describe the structure of carbohydrates, proteins and lipids as large molecules made up from smaller basic units: starch and glycogen from simple sugar; protein from amino acids; lipid from fatty acids and glycerol
(you do not need to learn the diagrams, I just put them there for better understanding)
Carbohydrates (starch and glycogen)
simple sugars (monosaccharides), such as glucose (a basic carbohydrate), join together to make more complex polysaccharides and disaccharides...
Proteins
proteins are made up of amino acids
Lipids
made from three fatty acids and glycerol
2.5 identify the chemical elements present in carbohydrates, proteins and lipids (fats and oils)
Proteins consist of Carbon, Hydrogen, Oxygen, Sulphur, Phosphorus and Nitrogen
Carbohydrates and lipids consist only of carbon, hydrogen and oxygen
Carbohydrates and lipids consist only of carbon, hydrogen and oxygen
2.4 compare the structures of plant and animal cells
(NOTE: Plant cells also contain chloroplasts, a vacuole and a cell wall)
2.3 describe the functions of the nucleus, cytoplasm, cell membrane, cell wall, chloroplast and vacuole
Nucleus - contains genetic material which controls the activities of the cell
Cytoplasm - most chemical processes take place here, controlled by enzymes
Cell membrane - controls the movement of substances in and out of the cell
Cell wall (only plants) - strengthens the cell
Chloroplasts (only plants) - contain chlorophyll. Chlorophyll absorb light energy for photosynthesis
vacuole (only plants) - this is filled with cell sap to help keep the cell turgid (not floppy, basically)
2.2 describe cell structures, including the nucleus, cytoplasm, cell membrane, cell wall, chloroplast and vacuole
Animal cell
- nucleus in the centre
- surrounded by cytoplasm
- around the outside edge is the cells membrane (animal cells do not have cell walls)
Plant cell
- vacuole in the centre
- surrounded by cytoplasm - within this is the nucleus and chloroplasts
- surrounding this is the cell membrane
- around the cell membrane is the cell wall
(NOTE: plant cells have 3 extra things that animal cells do not... a vacuole, chloroplasts, a cell wall)
- nucleus in the centre
- surrounded by cytoplasm
- around the outside edge is the cells membrane (animal cells do not have cell walls)
Plant cell
- vacuole in the centre
- surrounded by cytoplasm - within this is the nucleus and chloroplasts
- surrounding this is the cell membrane
- around the cell membrane is the cell wall
(NOTE: plant cells have 3 extra things that animal cells do not... a vacuole, chloroplasts, a cell wall)
2.1 describe the levels of organisation within organisms: organelles, cells, tissues, organs and systems
The level of organisation is as follows (from smallest to largest)...
Organelles, cells, tissues, organs, organ systems
Organelles - they are highly organised structures of molecules that have a specific function within a cell. An example is mitochondria, their function is to generate energy for our bodies cells.
Cells - they are made up of organelles, described as a functional unit. Cells are the basis of living things. An example is a skin cell.
Tissues - tissues are a collection of similar cells that all serve a common function. An example is glandular tissue, which produces substances such as enzymes and hormones.
Organs - they are made up of several kinds of tissues that act together to form a functioning unit. An example its the heart.
Organ systems - systems are a group of several organs, for example the cardiovascular system is made up of the heart, blood and blood vessels.
Organelles, cells, tissues, organs, organ systems
Organelles - they are highly organised structures of molecules that have a specific function within a cell. An example is mitochondria, their function is to generate energy for our bodies cells.
Cells - they are made up of organelles, described as a functional unit. Cells are the basis of living things. An example is a skin cell.
Tissues - tissues are a collection of similar cells that all serve a common function. An example is glandular tissue, which produces substances such as enzymes and hormones.
Organs - they are made up of several kinds of tissues that act together to form a functioning unit. An example its the heart.
Organ systems - systems are a group of several organs, for example the cardiovascular system is made up of the heart, blood and blood vessels.
Thursday 10 March 2016
1.3 recall the term ‘pathogen’ and know that pathogens may be fungi, bacteria, protoctists or viruses.
Any micro-organism that causes disease is pathogenic, it is known as a pathogen. Therefore, pathogens are simply micro-organisms that cause disease.
Fungi, bacteria, protoctists and viruses are all micro-organisms, and some cause disease. Therefore, some fungi, bacteria, protoctists and viruses are pathogens (or are pathogenic).
It is importants to remember that not ALL fungi, bacteria and protoctists are pathogens, as not all of them cause disease but all viruses are, as they all cause disease.
Fungi, bacteria, protoctists and viruses are all micro-organisms, and some cause disease. Therefore, some fungi, bacteria, protoctists and viruses are pathogens (or are pathogenic).
It is importants to remember that not ALL fungi, bacteria and protoctists are pathogens, as not all of them cause disease but all viruses are, as they all cause disease.
1.2 describe the common features shared by organisms within the following main groups: plants, animals, fungi, bacteria, protoctists and viruses
EDIT: Hi guys, I was just going through the blog and I CANNOT work out why the formatting on this post is so strange (the text keeps coming up as different fonts/colours) - I wrote it all at the same time so I don't see why this is happening. I've tried to resolve but with no luck, sorry:(
For each group (plants, animals, fungi, bacteria, protoctists and viruses) you will need to be able to...
For each group (plants, animals, fungi, bacteria, protoctists and viruses) you will need to be able to...
- give and describe the common features of the organism
- give examples
They are as follows...
Plants
Animals
Fungi
Bacteria
Protoctists
These are microscopic single-celled organisms. Some, like Amoeba, that live in pond water, have features like an animal cell, while others, like Chlorella, have chloroplasts and are more like plants. A pathogenic example is Plasmodium, responsible for causing malaria
Viruses
YES this is a lot of information to remember, I find it easiest to remember by drawing up either a mind map or a table, that way you can easily see and compare which organisms store carbohydrate as glycogen, for example.
- These are multicellular organisms
- Their cells contain chloroplasts and are able to carry out photosynthesis
- Their cells have cellulose cell walls
- They
store carbohydrates as starch or sucrose
Animals
- These are multicellular organisms
- Their cells do not contain chloroplasts and are not able to carry out photosynthesis
- They have no cell walls
- They usually have nervous coordination and are able to move from one place to another
- They often store carbohydrate as glycogen
Fungi
- These are organisms that are not able to carry out photosynthesis
- Their body is usually organised into a mycelium made from thread-like structures called hyphae, which contain many nuclei
- Some examples are single-celled
- Their cells have walls made of chitin
- They feed by extracellular secretion of digestive enzymes onto food material and absorption of the organic products
- This is known as saprotrophic nutrition
- They may store
carbohydrate as glycogen
Bacteria
- These are microscopic single-celled organisms
- They have a cell wall, cell membrane, cytoplasm and plasmids
- They lack a nucleus but contain a circular chromosome of DNA
- Some bacteria can carry out photosynthesis but
most feed off other living or dead organisms
Protoctists
These are microscopic single-celled organisms. Some, like Amoeba, that live in pond water, have features like an animal cell, while others, like Chlorella, have chloroplasts and are more like plants. A pathogenic example is Plasmodium, responsible for causing malaria
Viruses
- These are small particles, smaller than bacteria
- They are parasitic and can reproduce only inside living cells
- They infect every type of living organism
- They have a wide variety of shapes and sizes
- They have no cellular
structure but have a protein coat and contain one type of nucleic acid, either
DNA or RNA
YES this is a lot of information to remember, I find it easiest to remember by drawing up either a mind map or a table, that way you can easily see and compare which organisms store carbohydrate as glycogen, for example.
Wednesday 9 March 2016
1.1 Understand that living organisms share the following characteristics
-
– they require nutrition
-
– they respire
-
– they excrete their waste
-
– they respond to their surroundings
-
– they move
-
– they control their internal conditions
-
– they reproduce
-
– they grow and develop.
These are just the 8 characteristics of life, a good way to remember them is by using the anagram 'M.R.S.G.R.E.N' (sometimes known as M.R.S.N.E.R.G), or make up your own if you find it easier to remember.
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