B3 Biology :)

Covers a small chunk of B3. 1.1-6 and 2.1-7

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Exchange of materials

Types of Exchange (Gaseous & Liquid):

Active Transport

  • This uses energy from aerobic respiration, takes jazz against concentration gradient.


  • Diffusion of liquid through a partially permeable membrane.


  • Net diffusion of substance from area of high concentration to low concentration.
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Exchange of Materials - In (small) Intestine


  • Found in small intestine
  • look like willis
  • have large surface area
  • rich blood supply
  • are moist and have thin walls (less distance to travel for diffusion)
  • absorb food into blood stream through diffusion and active transport
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Exchange of Materials - In Aveoli


  • Found in lungs,
  • small 'air sacs' have a rich blood supply
  • are moist for diffusion to occur more quickly and effectively
  • have large surface area
  • thin walls and are very close to capillaries - oxygen diffuses into the capillaries and Co2 back into the lungs.
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Exchange of Materials in Other Organisms

Other Organisms

  • All living things have one thing in common, gas exchange.
  • The gas exchange is also important and are similar in organisms. They have:
  • large surface area
  • their membranes of which soluble stuff diffuse across are thin
  • gasses are transported away quickly to maintain a high concentration gradient
  • they are moist.
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Gas Exchange in Plants


  • Plants exchange gasses through their stomata which are opened and closed by guard cells.
  • Leaves are flat and thin to obtain lots of sun light and so gasses do not need to diffuse far.
  • water and mineral ions are taken up by root hairs which project into the soil and have a large surface area.
  • water can evaporate from leaves - this is called transpiration.
  • Water is mostly lost through the stomata, but if too much water is lost, the plant will wilt
  • most water is lost on hot, windy or dry days.
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The Human Circulatory System

The Circulatory System

  • Blood is pumped around the body by the heart
  • Oxygenated blood goes from the lungs to the heart and then around the body - these are two different circulatory systems.
  • De-oyxanated blood is pumped from the body to the heart and then to the lungs.
  • Remember - arteries - away from the heart, veins to the heart.
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Human Blood


  • There are 3 different things found in 'blood'
  • Platelets - create clotting or scabs.
  • Plasma - carries around dissolved substances, like glucose, urea and Co2.
  • Finally red blood cells - they have no nucleus, have a large surface area and transport oxygen which is carried by haemoglobin which when combined with oxygen becomes - oxyhaemoglobin.
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Effect of Exercise on the Body

  • During use energy to contract, the more exercise they do, the more energy they need.
  • When you exercise you use up more glucose and oxygen and you need to displace/excrete more carbon dioxide and lactic acid.
  • When you need this to happen, your heart rate increases along with your breathing and blood supply goes by and large to the actively respiring muscle cells.
  • If you become too tired whilst exercising and cannot get enough oxygen, your muscles start to respire anaerobically. This is the equation for aerobic respiration Oxygen + Water --> Carbon dioxide (+ Energy) in anaerobic respiration the equation is Glucose --> Lactic acid (+ Energy)
  • Lactic acid is acidic to the human body and so needs to break it down using oxygen to form water and water. therefore when someone undergoes anaerobic respiration they form a oxygen dept, for they still need to take in oxygen to break down the lactic acid.
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Human Kidney

The kidneys filters the blood, excreting substances which the body does not want. The kidney first filters all of the blood and then reabsorbs substance which the body needs (like mineral ions and glucose) through active transport.


Basically an artificial kidney which, through diffusion and osmosis (through a partially permeable membrane) filters the blood, but does not need to reabsorb any substances. Dialysis restores the concentration of substances in the blood back to normal, but needs to be carried out regularly. If your kidneys failed, then you'd die, but through a dialysis machine you'd survive.

Kidney transplants:

Better than dialysis, but you need a donor who has the same blood type and same tissue match. However, the immune system is likely to reject a new kidney, to stop this the recipient must take drugs to suppress the immune system, be kept in a sterile environment to prevent him/her from falling ill for they have a weak immune system because of the drugs, the recipient's bone marrow has to be treated with radiation to stop it from producing white blood cells.

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You can grow microbes on a small scale using algar in petri dishes and certain carbohydrates and minerals for the microbes energy source, however, you must make sure that every thing is sterile so no harmful pathogens germinate along with the microbe you are trying to grow. Right temperatures for growth is about 25-30C in school incubators.

Yeast is a single-celled organism which creates water and carbon dioxide when it respires aerobically (used for bread making) however, when there is not enough oxygen yeast undergoes anaerobic respiration, creating ethanol and carbon dioxide, this is called fermentation (used for making alcohol.)

In the production of cheese and milk, bacterial is used. A culture is added to warm milk, and the milk has to stay warm for the culture to germinate and respire. When this occurs it turns the lactose (natural sugar in the milk) into lactic acid which makes the milk clotted and turn into yogurt or cheese.

Large scale microbe production: Microbes are produced on industrial scales in large fermenters, these fermenters are very carefully controlled: Air supply is sterile and contains oxygen, stirrer used to spread microbes and make sure microbes have even amount of oxygen and temperature, water cooled jacket stops the microbes from warming up too much and killing themselves, and a Ph and temperature monitor.

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Antibiotic production, Biogas and more Biofuels

Penicillin is made from the mould penicillium in a fermenter with sugar and jazz for extra energy and some extra nutrients like nitrogen. Penicillium the antibiotic only starts to get produced when most of the nutrients are used up.

Biogas is mainely methane - a flammable gas. Its created through the fermentation (and lots of microorganisms) of lots of waste substances, ranging from human excrement's to waste from the kitchen. Biogas can only be produced on a large scale with waste from sewage works or sugar factories.

Biofuel can be produced from the fermentation of sugar cane juices and glucose derived from maize starch by the action of a carbohydrate enzyme - ethanol is produced for this is anaerobic respiration. This ethanol can be distilled and used as a fuel for cars.


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