Unit 2 and 3 AQA Higher notes

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Unit 2
All organisms are made of cells.
Cell wall ­ strengthens cell
Permanent vacuole ­ filled with sap to support cell
Cytoplasm ­ chemical reactions
Cell membrane ­ controls movement in and out of cell
Chloroplasts ­ contains chlorophyll which absorbs light to make energy
Ribosomes ­ Protein synthesis
Nucleus ­ Genetic information ­ has a membrane extending from it onto which Ribosomes are
In human cells, cytoplasm sometimes contains mitochondria
Root hair cell has a large surface are for absorption of water and ions.
Palisade cells have lots of chloroplasts for photosynthesis
Xylem cells are long, thin, hollow cells. They contain no cytoplasm. They transport water
through the stem and root.
Nerve cells (neurones) are long and slender and can carry impulses over long distances.
The egg cells are very large to carry food reserves for embryos.
Sperm cells have a tail
Red blood cells have no nucleus so they have more space for haemoglobin. They also have a
large surface area.
White blood cells change shape to engulf and destroy microbes.
Cells are made up of water containing dissolved substances.
Enzymes control chemical reactions.
Enzymes are found in cytoplasm and in mitochondria which produce the energy of a cell.
Amoebae are single celled organisms.
Oxygen, carbon dioxide, food and waste products pass easily through cell membranes.
Diffusions requires no energy
High concentration ­ low concentration
Osmosis is movement of water from a dilute solution to a more concentrated solution
through a partially permeable membrane.
ONLY movement of water.
Osmosis gradually dilutes solutions
This happens in root hair cells.
Green plants make energy from the sun by photosynthesis
The plants need light, carbon dioxide, water and chlorophyll.
Glucose and oxygen is produced.
Carbon dioxide + Water (+ light + chlorophyll) Glucose + oxygen
Some of the glucose is used to provide energy via respiration but some is stored in the stem,
roots or leaves as insoluble starch

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Factors affecting photosynthesis are temperature, carbon dioxide concentration and light
A greenhouse controls these
A lack of nitrates will cause stunted growth
A lack of magnesium will cause chlorophyll shortage and leads to yellow leaves.
The transfer of energy is shown in a food chain
Pyramids of biomass are used because using numbers would be inaccurate
Biomass and energy are lost at every stage of a food chain because materials and energy are
lost in waste.…read more

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Amylase digests starch into sugars, protease digests proteins into amino acids and lipase
digests lipids into fatty acids and glycerol.
Bile is produced in the liver and stored in the gall bladder before being released into the
small intestine.
It neutralises acid do produce alkaline conditions in which the enzymes there work best
It emulsifies fats. (Breaks down large drops into small drops.) This enables the lipase to work
faster.…read more

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Ultimately, the sex of an individual is decided if the ovum is fertilised by an X-carrying sperm
of a Y-carrying sperm
The ovum is always an X-chromosome
Mitosis is the division of body cells to produce new cells.
This occurs in growth, repair and asexual reproduction.
Before the cell divides, a copy of each chromosome is made so the new cell has exactly the
same genetic information.
Meiosis occurs in the testes and ovaries. They divide to produce gametes for sexual
reproduction.…read more

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Unit 3
o Bronchus, branch of trachea
o Bronchiole, one of branches
o Rib muscles can raise and lower ribs
o Alveoli, air sacs, good blood supply, moist
Stomata are holes, guard cells close stomata
Hearty has double circulation.
Vein goes towards heart
Artery goes away from heart.…read more

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During exercise
o Arteries dilate
o Depth and rate of breathing increase
o Supply of oxygen and glucose increased
o Glycogen broken down.
Kidney controls concentration of dissolved substances in blood
Removes urea
Made of tubules and blood vessels.…read more

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Contains sugar and other nutrients in medium ­ used in growth before mould starts to make
o Protein rich food, made using Fusarium
o Grown in aerobic condition
o Biomass harvested
Biogas production needs anaerobic conditions
Needs organic or waste material containing carbohydrates
Many microorganisms used
Ethanol can be distilled to make fuel for cars ­ needs sugar cane juices or glucose from maize
Culture medium needs
o Carbohydrates
o Mineral ions
o Vitamins
o Proteins
Agar used…read more


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