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AQA GCSE Biology B3

What do both osmosis and diffusion involve? Movement of substances from a place of higher to lower concentration.
What is the role of stomata in the leaf? To allow carbon dioxide to diffuse into the leaf, and water vapour and oxygen to diffuse out.
What are the guard cells, ansd why does a plant need them? They control the size of the stomata, and close them if the plant is losing water faster than it can be replaced by the roots. Without them the plant would soon wilt.
How do the flattened shape of the leaf and air spaces inside help gases diffuse in and out? Flattened shape: increases area of exchange surface so it is more effective. Air spaces: Increase area of the exchange surface created by the walls of the cell, so there is more chance for carbon dioxide to get through.
What are the best conditions for transpiration and why? Hot, dry, and windy - because water vapour escapes using diffusion, so works best when the air outside is kept dry.
What is active transport? The process by which a cell with a high concentration of a substance can gain even more, and take it up against the concentration gradient. This involves energy.
How are root hair cells adapted for absorbing water and minerals? The hairs give the plant a big surface area for absorbing water and mineral ions.
When is active transport used in the gut? When there is a low concentration of nutrients in the gut, but a high concentartion in the blood.
What are villi, and what is their role in the gut? They are finger like projections in the gut that increase the surface area for absorption to take place.
How are the surfaces of the lungs adapted for quick diffusion? They are moist and thin, as diffusion takes place more quickly through a wet surface.
How is the large surface are of the lungs provided? By millions of alveoli, which have a spherical shape to provide a large surface area, and a good blood supply to maintain the concentration gradient for diffusion, by removing oxygen and bringing carbon dioxide.
What do oxgen and carbon dioxide diffuse into? Oxygen diffuses into capillariesurrounding the alveoli, while carbon dioxide diffuses back ionto the lungs.
What 4 features do all living organisms have in common to help with gas exchange? -Large surface area -Moist -Gases are transported away quickly to maintain a high concentration gradient. -The membranes that gases diffuse across are thin.
Briefly describe Arteries. They have a small lumen, a thick layer of muscle, and thick walls. They carry blood away from the heart towards the organs. They stretch, the blood is forced through them and then they snap back into place, creating a pulse.
Briefly describe Veins. They have a large lumen, often have valves,and thin walls. THey carry blood back to the heart, and have valves to prevent back flow of blood.
Briefly describe Capillaries. They have a narrow lumen and walls a single cell thick, so that substances can easily diffuse in and out of the blood and your cells.
Describe the route that blood takes through the heart. Vena Cava, Right Atrium, Right ventricle, Pulmonary artery, LUNGS, Pulmonary vein, Left atrium, Left ventricle, Aorta, REST OF BODY.
What is haemoglobin, and what happens to it in the lungs? A red pigment in red blood cells. In the lungs, it is combined with oxygen to make oxyhaemoglobin.
What is oxyhaemoglobin used for? Why don't red blood cells have a nucleus? When cells are respiring, the oxyhaemoglobin breaks down and releases the oxygen for respiration. Red blood cells have no nucleus so more haemoglobin can be packed into them.
What does blood plasma transport? -carbon dioxide to the lungs -the (soluble) products of digestion to all living cells in the body -urea, made by the liver, to the kidneys for excretion.
What do muscles need during exercise and why? -more energy so that they can contract -more glucose and oxygen at a quicker rate (for more respiration) -quicker removal of carbon dioxide
How does your body adapt to cope with this? -Heart rate increases and blood vessels dilate to allow more oxygen and glucose to reach muscles -Breathing rate and the depth of breathing increases, to allow greater takeup of oxygen and release of carbon dioxide. -Glycogen is used up.
What happens to your muscles if you use them over a long period? They will become tired and fatigued
What happens to your muscles if you use them over a long period? They will become tired and fatigued
What causes anaerobic respiration to take place? When your muscles cannot get enough oxygen for aerobic respiration
What is the waste product of anaerobic respiration, and how is it broken down? Lactic acid (which causes fatigue), is broken down by taking in a lot of oxygen, known as oxygen debt - This breaks it down into carbon dioxide and water.
What is the role of the kidneys in the body? To filter the blood, excreting substances you don't want, and keeping those that the body needs.
What si urea, and where is it produced? Made by the liver from excess amino acids
What is the role of the renal artery? Brings blood containing urea and other substances in solution to the kidney
What is the role of the renal vein? Carries blood away from the kidney, after urea and other substances have been removed from the blood by the kidney
What are the roles of the ureter, bladder and urethra? urine passes from the kidney to the bladder through a tube called the ureter. It is stored in the bladder before passing through a tube called the urethra to the outside of your body.
What happens to the sugar, dissolved ions and water needed by the body after filtering, and how is this sometimes done? They are reabsorbed - sometimes by active transport if against the concentration gradient.
What is the role of a dialysis machine? To carry out the same job as the kidneys - the blood flows through partially permeable membranes. It restores the concentration of substances in the blood back to normal.
What does dialysis fluid contain, and why? It contains the same concentration of useful substances that the patients blood does, so that they are not filtered out, so aren't reabsorbed. Urea isnt filtered out.
What is the main disadvantage of dialysis? It needs to be carried out at regular intervals.
Where are donor kidneys found? Often from people who have just died.
Where is the new kidney placed in a kidney transplant? In the groin, and attached to the blood vessels and the bladder
How do doctors try to stop the immune system rejecting the new kidney? The patient's bone marrow is treated with radiation to stop white blood cell production. The recipient takes immunosupressant drugs. The recipient is kept in sterile conditions after the operation, to prevent infection.
What are microorganisms grown on in petri dishes, and what does it contain? Agar - contains carbohydrates as an energy source, but may also contain some minerals, proteins, vitamins and supplementary (extra) nutrients.
How do you prepare a pure or uncontaminated culture? Sterilise petri dishes, agar, and sterilise inoculating loops by passing through a flame. Hold the lid of a Petri dish in place with adhesive tape.
What temperature should cultures be incubated at in schools and colleges? Why is it higher in industry? 25*C, to promote faster growth.
What does yeast do in the presence of oxygen? Respire aerobically and reproduce quickly
What does yeast do when oxygen is absent? Respire anaerobically and produce ethanol and carbon dioxide - called fermentation.
What is used as the carbohydrate energy for yeast when beer is brewed, and what process does it go through? What is used to give flavour? Starch - first broken down into sugars in the barley grains by enzymes during the germinating process. Hops are used to give flavour.
What is used as the energy source when making wine? The natural sugars in the grapes
What are the three stages of making yoghurt? Bacteria are added to warm milk. The milk sugar (lactose) is fermented by the bacteria, producing lactic acid. The lactic acid causes the milk to solidify (clot) and yoghurt is formed.
Created by: Rayrayy