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Class notes Biology Grade 9-1 GCSE Combined Science, ISBN: 9781782945741
These are GCSE Biology Notes made using the revision questions at the end of topic B1.
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B1 - CELL BIOLOGYCELLS & MICROSCOPY )-
● Five subcellular structures: nucleus, mitochondria, ribosomes, cell membrane,
cytoplasm.
● 3 structures plant cells have: cell wall, permanent vacuole, chloroplasts.
● Genetic material: found in the nucleus in animal cells, found in the cytoplasm.
● Bacteria are prokaryotes
● An electron microscope has a higher resolution than a light microscope
DIFFERENTIATION & DIVISION )-
● Cell differentiation is the process by which a cell becomes specialised for its job.
● A sperm cell is adapted to swim to an egg cell, by its long tail, streamlined head and
mitochondria to provide the energy needed.
● Nerve cells are a certain shape to connect to other cells, and form a network.
● Chromosomes are coiled up lengths of DNA molecules
● The cell cycle is when body cells in mukticellular organisms divide to produce new
cells.
● Mitosis is used by multicellular organisms to grow or replace cells
● 2 ways that embryonic cells can be used to cure diseases is by using them to create
insulin-producing cells (diabetes) and nerve cells (spinal injuries)
● Some people may be opposed to the use of human embryos because embryos are
potential life, and should not be used for experiments.
EXCHANGING SUBSTANCES )-
● Diffusion is the gradual movement of particles from places where there are lots of
them to places where there are few of them.
● 3 substances that diffuse through cell membranes: glucose, amino acids, water. 2
substances that can’t: starch, proteins
● Water molecules move by osmosis.
● In diffusion, substances move down a concentration gradient. However, active
transport moves substances against a concentration gradient.
● 3 adaptations of exchange substances: thin membrane, large surface area, lots of
blood vessels
● Villi in the small intestine are adapted for absorbing digested food, because they
hace a single layer of surface cells and a very good blood supply
● Leaves are adapted to maximise CO2 absorption due to stomata, where it diffuses
through.
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