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Additional Biology
Cells
Animal and plant cells
Most animal cells contain a:
o Nucleus
o Cytoplasm
o Cell membrane
o Mitochondria
o Ribosomes

Plant cells contain all the structures seen in animal cells as well as:
o A cell wall
o Chloroplasts
o A permanent vacuole

The tables below show…

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Dissolved substances move in and out of cells by diffusion, osmosis and active transport.

Diffusion
Diffusion is the passive net movement of particles from an area where they are at a high
concentration to an area where they are at a lower concentration.

Osmosis
Osmosis is a special case of…

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Radiation from the Sun is the main source of energy for all living things. The Sun's energy is
captured and used by plants during photosynthesis.
The mass of living material at each stage of a food chain is less than at the previous stage.
The biomass at each stage can…

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Biomass and energy are lost at each stage of a food chain. The efficiency of food production
can be improved by reducing the number of stages in our food chains. It would be most
efficient if we all just ate plants.
If you stop animals moving about and keep them…

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The constant cycling of carbon in nature is known as the carbon cycle.
Carbon dioxide is removed from the atmosphere by photosynthesis. It is returned to the
atmosphere through respiration and combustion.
The energy originally captured by green plants is eventually transferred into consumers,
decomposers or as heat into the…

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Aerobic respiration involves chemical reaction which use oxygen and sugar and release
energy. The reaction is summed up as:

Glucose + oxygen > carbon dioxide + water [+ energy]

Most of the reactions in aerobic respiration take place inside the mitochondria.

Enzymes in digestion
Enzymes catalyse the breakdown of large…

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The enzymes made in the pancreas and the small intestine work best in alkaline conditions.
Bile produced by the liver neutralises acid and emulsifies fats.

Making use of enzymes
Some microorganisms produce enzymes which pass out of the cells and can be used in
different ways.
Biological detergents may contain…

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The pancreas produces the hormone insulin, which allows glucose to move from the blood
into the cells.
In diabetes, the blood glucose may rise to fatally high levels because the pancreas does not
secrete enough insulin. It can be treated by injections of insulin before meals.



Inheritance
Cell division and…

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Embryonic stem cells (from human embryos) and adult stem cells (from adult bone marrow)
can be made to differentiate into many different types of cells.

Using stem cells
o Using stem cells, scientists may be able to culture new types of cells, like nerve cells
for people who have been…

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o Meiosis is a special form of cell division where the chromosome number is reduced
by half.
o When a cell divides to form gametes, the first stage is very similar to mitosis.
o The chromosomes are copied so there are four sets of chromosomes. The cell then
divides twice…

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