Biology B2

Human, evolution and the enviroment. Alleles, chromosomes, osmosis.

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Cells ( animal and plant)

Nucleus - controls the cells activities

Cytoplasm - chemical reations take place

Cell membrane - controls what passes in and out

Mitochondria- energy is release through respiration

Ribsomes- protein synthesis happens

Plant cells also have

Cell wall - used to strengthen cell

Chloroplasts - absorb light energy to make food

Permanent vacuole - filled with cell sap

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Diffusion and Osmosis

Osmosis is only associated with water. It is the movemet of water from low concentation to high.

Diffusion spreads gas particles;

They go from high concentration to low concentration

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Equation------->carbon dioxide +water= glucose+oxygen

You need;

Light (converts it all to glucose)

carbon dioxide


chlorophyll (found in chloroplasts)


Mineral ions

Nitrates make amino acids which form proteins. Proteins help the plant to grow

Magnesium is used for chlorophyll production (yellow leaves without)

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What affects photosynthesis?


Carbon dioxide

Light intensity


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Protease - Stomach, pancreas and small intestine, it breaks down proteins to make amino acids

Lipase - Pancrease and small intestine they digest lipids(fats) and produce glycerol and fatty acids.

Amylase - produced in small intestine, pancreas and salivary glands, they digest starch and make sugars

Carbohydrase converts starch into glucose syrup

Isomerase converts glucose into fructose

Bile is prodcued in the liver, stored in the gall bladder and released into the small intestine

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Controlling body conditions

Humans control blood, sugar, water, ion content and temperature.


Diabetes = a condition in which the pancreas cant produce enough insulin


Body temperature is monitored by receptors in the brain ( thermoregulatory centre)

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Human Body Cells

46 chromosomes ----> 23 pairs

Gametes are sex cells with 23 chromosomes

Zygotes have 46 chromosomes


Alleles=variations of genes

Dominant and recessive


Differentiation - cells carry out a specific function. Stem cells have not differentiated

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Mitosis =  the division of body cells to produce new cells

They are identical to their parent. (identical genetic info)

After fertilisation, a zygote will divide many times through mitosis to form a new cell.


Meiosis -  cells in the testes and ovaries divide to produce gametes.

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