AQA B3 Complete

This is the final section of Biology for all of those lovely people who have chosen to take Triple Science on the AQA course! Hope you enjoy it :P

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  • Created by: alex
  • Created on: 18-05-10 21:17

Active Transport

  • It goes against the concentration gradient, so it goes from a low concentration to a high concentration. You can also say it goes up a concentration level.
  • It uses energy which comes from mitochondria.
  • It is used in the intestine and kidneys.
  • It enables cells to absorb ions from dilute solutions
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They are tiny air sacs in the lungs and are ready for gaseous exchange because:

  • They have a large surface area
  • They are moist
  • They are near the blood capillaries so oxygen can diffuse quickly and easily into the blood. And Carbon dioxide can diffuse into the lungs.
  • They have very thin walls so the distance for diffusion is shorter
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  • They are in the thorax and are protected by the ribcage.
  • The breathing system takes air in and out of the body so that oxygen from the air can diffuse into the bloodstream.
  • Carbon dioxide can diffuse out of the bloodstream and into the air.
  • The lungs are separated from the abdomen by the diaphragm.
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  • Breathing out = Ribcage Down, Diaphragm Up
  • Breathing In = Ribcage Up, Diaphragm Down
  • Air moves in the mouth, down the trachea, down the bronchi and further down into the bronchioles then it finally arrives at the alveoli.
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  • Villi are in the gut (intestine)
  • Villi help absorb the products of digestion.
  • They use active transport to obtain useful substances e.g sugar.
  • They have large surface area so that digested food is absorbed a lot more quickly into the blood.
  • They are always moist
  • They are close to a large network of capillaries so diffusion is as rapid and efficient as possible.
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  • The stomata has holes in the underside of leaves that allow carbon dioxide out, but when that happens water vapour and oxygen escape from the stomata.
  • So guard cells stop to much water being lost in transpiration and let the carbon dioxide out.
  • Transpiration happens more quickly in hot, dry, windy conditions.
  • Plants may wilt if more water is lost than is gain from the roots because the cells get less rigid.
  • The surface are of roots are increased by root hairs.
  • Surface area of the leaves is increased because of the flattened shape and internal air spaces.
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  • There are small blood vessels in gills which allows gases to be exchanged.
  • The gills have a rich blood supply and are always moist.
  • Out of the water the gill stacks collapse so there is not surface area to get all the oxygen needed.
  • Carbon dioxide diffuses out of cells because it's a higher concentration in the cells and oxygen diffuses into the cells and binds with haemoglobin where it is transported to the cells in the blood.
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Circulatory System

  • The pulmonary system, use the pulmonary artery to take de-oxygenated blood from the heart to the lungs (where it is oxidised) & then returns back to the heart by the pulmonary vein. The right side of the heart pumps blood out of the heart & it collects oxygen and removes carbon dioxide.
  • The Circulatory system takes blood from the heart & transports it everywhere around the body (apart from the lungs) to supply oxygen. The part that the blood goes to in the heart is the left side.
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Blood Vessels

  • Veins carry blood to the heart so they carry de-oxygenated blood. They can stand low pressures, so the veins have valves so there is no back flow. They also have; very thin walls, no pulse, nothing diffuses in or out of it and there is a slow blood flow.
  • The pulmonary vein carries oxygenated blood back from the lungs.
  • Arteries carry blood away from the heart so they carry oxygenated blood. They can stand high pressures, so there is no valves. They also have; very thick walls, a pulse, there is a fast blood flow and nothing diffuses in or out of it.
  • The pulmonary artery carries de-oxygenated blood to the lungs.
  • Capillaries are tiny blood vessels that carry blood through the organs and allow exchange of substances with all living cells in the body. They have; 0.001mm thin walls, no pulse, materials diffuse out, blood flow slows down and there is no valves.
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  • White blood cells fight infections
  • Red blood cells are biconcave and transport oxygen from the lungs to the organs and they have no nucleus to allow more space for the oxygen.
  • The red pigment in red blood cells is called haemoglobin and in the lungs it becomes oxyhaemoglobin.
  • Plasma is a pale-straw coloured liquid which transports; carbon dioxide from organs to the lungs, soluble products of digestion from the small intestine to other organs and, urea from the liver to the kidneys.
  • A lack of iron in the diet means haemoglobin can't be made; this leads to anaemia, where the person always feels tired and may be pale because their blood can't carry enough oxygen.
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  • It increases the heart rate which pumps more oxygen to cells.
  • Breathing rate increases allows more oxygen to be supplied to the blood and get rid of carbon dioxide quicker.
  • Arteries dilate so there is more blood access to the cells to provide oxygen and glucose and carries away more waste carbon dioxide.
  • Glycogen is used up, it is the energy released during respiration and it allows the muscles to contract
  • Not enough exercise can lead to high blood pressure and heart disease.
  • Anaerobic respiration is used if there's not enough oxygen. However, muscles get tired quicker and don't release as much energy. Glucose --> Energy+Lactic Acid
  • After using anaerobic respiration lactic acid needs to be broken down and the amount of energy needed to break it down is called oxygen debt. Lactic Acid+Oxygen --> Carbon Dioxide+Water
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  • Ultrafiltration - High pressure builds up and squeezes water, urea ions, ions and sugar out of the blood and into the Bowman's capsule. Then the membranes, the blood vessels and the Bowman's capsule act like a filter so things like protein and blood cells aren't squeezed out.
  • Reabsorption - As liquid flows along the nephron, useful substances are re-absorbed back in the blood. Sugar is re-absorbed using active transport. Ions and water re-absorb too.
  • Release - Remaining substances continue out of the nephron, into the urethra and down into the bladder as urine.
  • The kidneys prevent toxins getting into the blood.
  • They control the level of water and the concentration of ions in the blood.
  • They also produce urine.
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Kidney Dialysis

Dialysis Machine:

  • Filter the blood
  • They keep the concentration of dissolved substances in the blood at normal levels
  • The patients blood is placed next to a permeable barrier, surrounded by dialysis fluid. The fluid has the same concentration of dissolved ions and glucose as healthy blood.
  • Unfortunately this has to be done 3 times a week for about 3-4 hours
  • It is also very expensive

Kidney Transplant:

  • It can be rejected by the patients immune system, so a kidney is chosen with a tissue type similar to that of the patient.
  • Bone marrow is zapped with radiation to stop white blood cells being produced.
  • The patient also has to take drugs that suppresses the immune system.
  • After the operation the patient has to be in completely sterile conditions for a few weeks.
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Advantages and Disadvantages


  • Cheap once, but costs with repetition
  • It's a continuous process
  • You have to be connected to a machine
  • You have to follow a careful diet
  • However it doesn't need invasive treatment
  • Rejection is not an issue
  • You don't have to find a donor
  • Immune suppressant drugs aren't needed


  • Expensive but only done once
  • Rejection is possible
  • No need to follow a careful diet
  • Requires a suitable donor
  • It is an invasive process
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  • Food is provided
  • Air is piped in to supply oxygen
  • There's a stirrer to keep the temperature constant because the micro-organisms make heat by respiration
  • Monitoring the pH so the micro-organisms can thrive
  • Sterile conditions must be met so that no cross contamination occurs
  • The micro-organisms can't sink to the bottom so the stirrer keeps them moving
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  • It is an antibiotic made by growing mould in a fermenter
  • The mould is grown in a liquid culture medium containing sugar and other nutrients
  • The sugar is used up as the mould grows
  • The mould only starts to make penicillin after using up most of the nutrients for growth.
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Means protein from fungi, it's a type of single celled-protein.

  • It's used to make meat substitutes
  • Fusarium is the main type of Mycoprotein
  • It's grown in fermenters using glucose syrup as food. The food is obtained by digesting maize starch with enzymes.
  • The fungus respires aerobically, so oxygen is supplied, so is nitrogen and other minerals.
  • The fermenter is sterilised using steam. So, the incoming nutrients are heat sterilised and the air supply is filtered.
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  • It is a single celled fungus
  • It can respire with or without oxygen:
    • Anaerobically - Glucose --> Ethanol + Carbon Dioxide + Energy
    • Aerobically - Glucose + Oxygen --> Carbon Dioxide + Water + Energy
  • It is used in dough to make bread. It converts sugars to carbon dioxide and ethanol, but the carbon dioxide is used for making bread, not ethanol.
  • The ethanol is used to make alcoholic drinks.
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Fuels from Micro-organisms

  • They can be made by fermentation - its when yeast or bacteria break sugars down anaerobically.
  • Ethanol is made by the fermentation of sugar.
    • Glucose --> Ethanol + Carbon Dioxide + Energy
    • In some countries like Brazil, they use ethanol and petrol in their cars to fuel it and they call it Gasohol.
  • Biogas is made up of 70% methane and 30% carbon dioxide.
  • To make Biogas on a small scale, plant and animal waste are used.
  • To make Biogas on a large scale, sludge is taken from the sewers and sugar factories.
  • Biogas is made in a Biogas generator.
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Biogas Generators

  • Batch generators make biogas in small batches. They're manually loaded up with waste, which is left to digest, and the by-products are cleared away at the end of each session.
  • Continuous generators make biogas all the time. Waste is continuously fed in, and biogas is produced at a steady rate. Continuous generators are more suited to large scale biogas projects.
  • No matter which generator it is it has to have; an inlet for waste material to be put in, an outlet for the digested material to be removed through and an outlet so that the biogas can be piped to where it is needed.
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Considering a generator?

Cost: Continuous generators are more expensive because waste has to be mechanically pumped in and digested material has to be mechanically removed.

Convenience: Batch Generators are less convenient because they have to be continously loaded, emptied and cleaned.

Efficiency: Gas is produced quickly at about 35 degrees. So if the temperature falls below this the gas production will be slower. Generators in some areas will need to be insulated or kept warm.

Position: The waste will smell during delivery, so generators should be sited away from homes. The generator is also best located fairly close to the waste source.

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Economic and Environmental Effects

  • Biofuels are greener alternative to fossil fuels, as they are carbon neutral.
  • Biofuels don't produce significant amounts of sulphur dioxide or nitrous oxides which causes acid rain.
  • The raw material is cheap and readily available
  • People can grow more crops because the digested material is a better fertiliser than undigested dung.
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Random facts taken from past papers

  • Glucose enters the blood from the gut and is filtered out of the blood. It is a small molecule that is reabsorbed by active transport.
  • Protein isn't present in a healthy persons urine because it cant pass through the kidney filter.
  • Water is re-absorbed in urine so it has more urea present than in the filtrate.
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Steph Underwood


Brill!! jw... for the exam do we need to know about fish?? i wasnt sure cos it hasnt really been on the past papers:S great notes Thankk Youu 5/5 :D



yh it hasnt really been on past papers... but my teacher says thats more of a reason to know it! its under the section 1.4 and its exchange of materials in other organisms. Basically what im saying is, it is best to know it, but its not the most important topic on there :) thanks



wow that is actually really good! but do we need to know about the pulmonary artery and stuff :s ***



yh i will add some more on the blood vessels :P thanks :D



do we need to kow about fish? :) because my teacher has not taught us anyhin about it.



only a little bit.. it hasnt been in past papers but it is in the text book! so its better to be safe than sorry :P good luck :D



i asked my teacher and we need to know nothing on fish :) x



ok :) i won't bother learning it then :P thanks x



love how were all on this site like one and two days before the exam haha :) cram people cram!!!!!!! good luck everyone :) x



this is so helpful ! good luck to everyone who has an exam !



haha these note helped me get an A last yr :D i want the same from my test that i had for alevels today :P

Shannon Tennant-Smith - Team GR





These are awesome notes! 

Thx, you're a star! 


Joshua Horscroft


Thanks Alex these are brill



This is some good stuff. Thanks

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