Biology Unit 2 revision

Key parts for revision biology 2 (AQA) , mainly higher teir. Try to make as visually friendly as possible and not go into too much detail. NOT COMPLETE.

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  • Created by: Abbie
  • Created on: 23-01-12 20:01

Animal & Plant Cells

Animal & Plant Cells:                                                                                  Nucleas - controls everything that happens inside the cell & contains the information to make new cells 

Cytoplasm - were the chemical reactions take place, controlled by Enzymes

Cell membrame - gives the cell its' shape and controls what substance enter and leave the cell.

Ribosomes - were the protiens are made.

Mitrochondria - found in the cytoplasm, were respiration happens.

Plant cells only:                                                                                                                      Cell wall - made of cellulose and strengthens the cell

Chloroplasts - are found in the cytoplasm, absorb light energy.

Vacuole - large sac, contains a watery fluid called cell sap.

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Specialised Cells

Some cells look different, this is because they have their own job. Cells specialise at embryonic stage.

Xylem cells: carry water up the stem so have small tubes.

Leaf Palliside Layer: Place of photosynthesis so contains plenty of chloroplasts.

Root hair cells: Are long and think to absorb water.

Nerve cells: Like wires to carry messages.

Sperm cells: Have a tail to swim to the egg.

Red blood cells: no nucleas more room for oxygen, has substance to carry blood.

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Tissues and Organs

Tissues are groups of identical cells that do the same job. Organs are made up of groups of tissues. A number or organs working together is a System.

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What is diffusion?

Diffusion is the movement of particles from a region of high concentration to a region of low cocentration untill evenly spread out.

An example in the human body is gas exchange in the lungs.

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What is osmosis?

Osmosis is the movement of water particles from a region of high concentration to a region of low concentration through a partially permamble membrame, untill evenly spread out.

An example in the human body is soluable substances into cells

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Biomass & Energy Losses

The efficiency of food production can be improved by reducing the number of stages in food chains.

Energy can be lost through out the food chain by:                                                not all of the food being edible 




thermoregulation in mammals

Intensive animal farming reduces energy loss by restricting movement and keeping animals in a temperature controlled enviroment.

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Carbon dioxide + Water = Glucose + Oxygen

There are 4 things plants need for photosynthesis:                                            Sunlight - provides the plany energy into chloroplasts                                         Water - Travels up the roots in the xylem by osmosis                                          CO2 - Enters the leaf by diffusion through the stomata                                            Chlorophyll - were sunlight is absorbed and photosynthesis happens.

Factors that affect photosynthesis:                                                                Temperature - best at 37 degrees as of Enzymes                                           Light- needed as sunlight provides energy to cells to photosynthesise           Carbon dioxide- which is the gas needed for photosynthesis                                 A way to remeber this is, plants need T.L.C

Plants need minerals: Nitrates combine with sugars to make amino acides for proteins (growth & repair) a sign of defiecncy is stunted growth. Magnesium is needed to make cholorphyll (photsynthesis), sign of deficency is yellow leaves.

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Useful materials like carbon and nitrogen are returned to the enviroment in waste materials or by death and decay. These materials are released when dead organisms are broken down (digested) by micro-organism, such as Fungi & Bacteria.

Fungi & Bacteria use enzymes to digest their food, and the soluable products are taken up, the decomposers absorb the food and use for growth and energy. These then may be eaten by other organisms and so the nutrients are passed on.

3 factors affect the rate of decay:                                                                       Oxygen- more oxygen the faster the rate of decay as oxygen used for respiration  Temperature- up untill 37-40 as enzymes work best (any lower is too slow)Moisture- more water the faster the rate of decay as more reproduction

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Carbon Cycle

- Carbon dioxide removed by photosynthesis

- Carbon dioxide used to make up carbohydrates, fats and proteins which make up the body of the plant

- Some is returned to atmosphere as plants repsire

- The plants are ate by animals so some carbon becomes fats and protiens

- Again, Carbon dioixde returned to atmosphere by respiration (animals)

- When plants & animals die they release waste, micro-organisms feed on their bodies and waste

- Carbon dioxide released into atmosphere by respiration (micro-organisms)

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Are biological catalysts, all enzymes are Proteins.

High temperatures can destroy the special shape of an active site in an enzyme, this means the substrate can no longer fit and the reaction cannot take place.

In Industry:                                                                                                          Biological detergents- Protease & Lipase digest fats and stains on clothes       Baby food- Contains protease so food is digested and babys can get amino acids Slimming food- Isomarase turns glucose into fructose (sweeter so less needed) 

Digestion:                                                                                                                  Amylase- breaks down Startch into Glucose, produced in Salivary Gland, Pancreas and Small Intestine                                                                                                   Protease- breaks down Protein into Amino Acids, produced in Pancreas, Stomach and Small Intestine                                                                                               Lipase- breaks down Fats into Fatty Acids and Glycerol, produced in pancreas and small intestine                                                                                                         

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Is made in the Liver and stored in the Gall Bladder.

Bile neautralises food as it is previously PH 1/2 from stomach.

Bile also emulsifies fats and helps breakdown lipase in breaking down fats for small intestine.

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Controlling Blood Sugar


Too High:

Pancreas detects increase in blood. Pancreas releases Insulin which causes the Liver to turn Glucose into insoluable Glycogen.

Too low:

Pancreas dectects fall in blood. Pancreas release Glucagon which causes the liver to turn Glycogen into soluable Glucose.

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Removal of Urea

Urea is made in the Liver and contains excess amino acids. Urea is poisnous so needs to be removed from the body. Urea travels via blood stream to kidneys were it is filtered from the blood and stored in the Bladder. Excreated as Urine.

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pretty good!! helping me alot!! :)


Really helpful!!!!!! Thank. You!


is this the old syllabus??????

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