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Unit Two
Cells
Most human cells like most other animal cells have:
Mitochondria: where most energy is released in respiration
Ribosomes: where protein synthesis occurs
Nucleus: controls cell's activities, contains genetic material
Cytoplasm: where most chemical reactions take place,
controlled by enzymes
Cell membrane: controls the passage of substances in…

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If plant cells lose a lot of water from their stomata or are placed in a concentrated
solution such as salt water, cells become plasmolysed as cell membrane pulls away
from cell wall, leading to wilting.
Plants
Plants can make their own food by photosynthesis.
Things required for photosynthesis:
1.…

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Used in respiration: releases energy
Making cell walls: glucose into cellulose
Making proteins: glucose combined with nitrates to make amino acids, then made
into protein
Stored as insoluble starch in cells

Plants need to take in a number of elements to stay alive. The most important are:
Hydrogen and oxygen:…

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Animals unable to behave naturally

Free-range farming
Advantages:
Can charge more for produce
Animals live more naturally
Disadvantages:
More land needed
Lower yield

A balance must be reached between a farmer's needs and the animal's welfare.

The Carbon Cycle and decay
Living things remove materials from the environment for growth…

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Once the microorganisms and detritus feeders have broken down the waste
products and dead bodies of organisms in ecosystems and cycled the materials as
plant nutrients, all the energy originally captured by plants has been transferred.

Enzymes
Enzymes are biological catalysts, (they increase the rate of a reaction).
Enzymes are…

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Small intestine Lipase Lipids (fats and Fatty acids Small intestine
oils) and glycerol
The stomach also produces hydrochloric acid, around pH2, (strong enough to
kill most microbes). The enzymes in the stomach work most effectively in
these acid conditions. Also produces protease, (inactive until secreted:
prevents it from digesting stomach…

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Homeostasis
Waste products which have to be removed from the body include:
Carbon dioxide produced by respiration: leaves via the lungs when we exhale
Urea produced by the liver breaking down excess amino acids: removed from the
blood by the kidneys, (by ultra filtration), into the urine, stored in the…

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If the core body temperature is too high:
Blood vessels supplying the skin capillaries dilate so that more blood flows through
the capillaries and more heat is lost.
Sweat glands release more sweat which cools the body as it evaporates.
If the core body temperature is too low:
Blood vessels…

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In body cells the chromosomes are normally found in pairs. Body cells divide by mitosis to
produce identical daughter cells during growth and repair.
Cells in reproductive organs, testes and ovaries in humans, divide to form gametes.
The type of cell division is called meiosis.
When a cell divides to…

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Homozygous recessive/ dominant: has two alleles that are the same, (two
recessive or two dominant).
Heterozygous: has two different alleles, one recessive, one dominant.
Phenotype: the physical appearance/ characteristic produced by a genotype.


Each gene codes for a particular combination of amino acids which make a specific protein.
Each person,…

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