Biology (Extension)

Everything in the extension part of biology

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  • Created by: Maddie
  • Created on: 17-05-12 09:23



Diffusion is the passive movement (no energy) of particles from a area of HIGH concentration to a area of LOW concentration (with the concentration gradient). Diffusion occurs in fluids (gases, liquids) and can be through a partially permeable membrane.

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Osmosis is the passive movement of WATER MOLECULES from a area of HIGH concentration (dilute solution) to a area of LOW concentration (concentrated solution)(with the concentration gradient). Can occur through a partially permeable membrane. 

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Active Transport

Active Transport

Active transport is the movement of particles from a area of LOW concentration to a area of HIGH concentration (against the concentration gradient). It requires ENERGY and transport proteins.

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Gas exchange in the lungs

Gas exchange in the lungs

CO2 diffuses from the blood and is breathed out

O2 is breathed in and diffuses into the blood.


Moist-so gases dissolve

*Thin walls-only small space to diffuse through

*Large surface area-effective exchange

*Good blood supply-maintains concentration gradient

 Capillary walls are 1 cell thick-easy diffusion 

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Absorbing food

Absorbing food

Substances are absorbed from food in the small intestine (illeum). The small intestine has a large surface area due to villi. Villi in turn are covered in microvilli, increasing the total surface area further. Villi have a good blood supply to maintain the concentration gradient and thin walls for easy  diffusion. However the body needs all sugars, so diffusion alone is not effective. Active transport is then needed to remove all remaining sugars from the small intestine. There are many carrier proteins and mitochondria in the cells on the edge of the villi, to provide for active transport. 

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Absorption in plants

Absorption in plants


*Through stomata (little holes mostly on bottom of leaf)

*Loss of water vapour is transpiration (quicker in hot, dry and windy conditions)

*Transpiration is measured with a potometer.

*Guard cells close stomata to prevent too much water vapour loss.

*Gases are exchanged in the air spaces next to the stomata. CO2 is absorbed. O2 and water vapour are released/lost.

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Absorption in plants

Absorption in plants


*Through root hair cells (Large surface area)

*Water in soil is in a more dilute concentration so the water moves via osmosis.

*Water moves into plant, until it reaches xylem vessels (dead cells), which transport it to leaves etc.

*As water is lost through transpiration in leaves it becomes a concentrated solution, so water from the roots replaces it.

*Plant will wilt if it doesn't contain enough water.

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*Go from the heart

*Very thick walls to withstand pressure from heart


*Go to the heart

*Contain valves to stop blood from flowing backwards


*Thin walls for easy absorption

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Exercise and the body

Exercise and the Body

O2 levels decrease during exercise due to more being used for respiration.

CO2 levels increase due to more respiration then decrease to due increased breathing rate.

Muscle arteries dilute so more oxygen and glucose can reach muscle cells.

Glucose levels drop during exercise due to it being used for respiration.

Breathing and heart rate increase during exercise, as the body needs more oxygen (from breathing) and glucose (from blood)

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Muscle fatigue is when you tire and lose level of response (basically just really tired).

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Aerobic respiration

Aerobic respiration

Glucose + Oxygen = Carbon dioxide + Water + ENERGY

Aerobic respiration releases more enegy, but requires oxygen.

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Anaerobic respiration

Anaerobic respiration

Glucose = Lactic acid + Carbon dioxide + ENERGY

Anaerobic respiration releases less energy, but is faster than aerobic respiration.

Anaerobic respiration is used during exercise when not enough oxygen is 'provided' for aerobic respiration to be effective.

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Oxygen debt

Oxygen Debt

Oxygen debt is created as anaerobic respiration makes lactic acid. The lactic acid needs to be removed from the body, and this requires oxygen. Oxygen debt is why you breathe heavily after exercise. The body uses oxygen to turn the lactic acid back into glucose.

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There are about 1 million tubules (nephron) in a kidney.

Substances are absorbed into the tubules from the blood.

All glucose is reabsorbed.

All urea is removed.

Water and ions are balanced depending on body concentration.

Protein and red blood cells are too large to pass into tubules.

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Kidney Dialysis

Kidney Dialysis

Dialysis is where a machine has blood pumped through it, and different substances are added to/ removed from the blood. This is great for people with kidney failure, however

*Not as effective as real kidneys
*Takes up lots of time (hospital visits etc)
*Diet still needs to be controlled
*Infection at access point (a vein and artery are connected for better blood supply)
*Lots of hospital visits (three times a week is average)

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Kidney transplant

Kidney Transplant

Basically someone gets 'given' someone elses kidney (as only one is really needed). This is even better than dialysis for most people as there are less time consuming hospital visits. However

*Risk of rejection (the average time a transplant kidney lasts is 8 years)
*You have to be healthy for the operation
*Immunosuppressant  drugs have to be taken for the rest of your life (this increases other illness risks)
*Operation risk
*Waiting list
*Has to be a tissue match 

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Bits about bacteria

Stuff about bacteria

Bacteria are single celled organisms. They are made up of cell wall, cytoplasm and nucleoid (sort of like a nucleus).
Bacteria multiply by dividing. This means they reproduce incredibly quickly.
A colony of bacteria is grown from a single cell
All bacteria have a optimum temperature, pH, oxygen concentration and require different nutrients (mostly carbohydrates and nitrogen). 

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People believed that living things could be produced after contact with non-living material (e.g. air). Abiogenesis was disproved by Pasteur using a swan neck flask (microbes settled in the bend and the broth stayed 'fresh').

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Biogenesis is living organisms produce other living organisms. Basically the opposite of abiogenesis. (Just remember abiogeneis came before biogenesis and a comes before b)

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Making Yoghurt

Making Yoghurt

*Thicken and homogenize milk (to break up fat droplets)
*Pasteurise milk (to kill bacteria)
*Cool milk to 40-46oC
*Add Streptococcus thermophilus or Lactobacillus bulgaricus or live yoghurt (to produce lactic acid)
*Incubate for 4-5 hours
*Needs anaerobic conditions
*Cool yoghurt to  slow bacteria.

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Yeast reproduce asexually by budding when supplies with glucose, oxygen and water at a temperature of 28oC.

Aerobically yeast use sugar and oxygen to produce carbon dioxide, water and energy (bread).

Anaerobically yeast breaks down sugar into ethanol, carbon dioxide and energy (alcohol).

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In industry large fermenters are used. Everything is sterilised and only pure cultures are used. This allows them to use temperatures that are closer to the microbes optimum.

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Mycoprotein fermentation

Mycoprotein fermentation

Mycoprotein is a source of protein for vegetarian. Mycoprotein is made up of Fusarium venenatum (a fungus) and the hyphae (bit like roots but on a mushroom).

*It doesn't need much space.
*Grows really fast (doubles every 5 hours).
*Efficient energy transfer through the food chain (only 1 link) 

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Biogas is produced by the anaerobic fermentation of natural waste. It can be used to provide heating and electricity. It uses up natural (animal or plant) waste. The left over can be used as crop fertiliser.

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Ethanol based biofuels

Ethanol based biofuels

These are carbon neutral fuels produced from living plant material. Starch is broken down to form glucose. Yeast is then added and produces carbon dioxide and ethanol.They can be used instead of petrol. They are carbon neutral as the plants take in carbon dioxide as they are growing, which is the same amount released when they are burnt.

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