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Biology b2 - Coggle Diagram
Biology b2
Cell cycle
the cells of your body divide to produce more cells, so your body can grow and replace damage cells . cells do this over and over again = cell cycle
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Synthesis - cell replicates its DNA so that when it splits during mitosis the 2 new cells will contain identical dna
molecule of DNA splits. bases on free - floating nucleotides pair up, crosslinks from between the new nucleotide bases and the old and new nucleotides join up so 2 new DNA molecules identical to original formed.
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MITOSIS
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Line up in centre and cell fibres full them apart. the 2 arms of each chromosomes go to opposite ends of the cell
Membranes form around each set, this becomes the nuclei
Cytoplasm divides, now 2 cells containing the same DNA, genetically identical
CELL DIFERENTIATION
Process by which a cell becomes specialised. most animal cells, the ability to differentiate is lost, but lots of plant cells don't lose it.
palisade leaf cell - they do most of the photosynthesis, packed with chloroplast. Tall shape means lot of surface area for absorbing co2 , thin shape means lots near the top so nearer the light
sperm - job to get male DNA near female DNA, long tail and streamline head to help swim. lots of mitochondria to provide lots of energy.
stem cells are undifferentiated, can divide by mitosis then differentiate, really important for growth found in adults but only in certain places not as versatile, can't turn into any cell.
in animals the only cells able to divide by mitosis are found in tissue called meristems - in roots and shoots. Meristems produce unspecialised cells that are able to divide and form any cell unlike humans. can become specialised to form tissues like xylem and phloem
transport system
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xylem - dead cells joined end to end, lumen (hole) in middle, strong, carry water and minerals.
transpiration - caused by evaporation and diffusion of water which creates a shortage of water in leaf, so drawn up through xylem. it is a side effect of the way leaves are adapted for photosynthesis. helps plant cool, provides constant supply of water for photosynthesis
transpiration effected by: an inc in light intensity, brighter, greater transpiration, inc photosynthesis, causing stomata to open, starts to close when it darkens as photosynthesis doesn't happen when dark.
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active transport
movement of particles across membrane against a concentration gradient ( low to higher conc) uses ATP
digestive system, higher concentration of nutrients in the gut they diffuse into blood, active transport allows nutrients to move into blood despite the concentration gradient.
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osmosis
net movement of water across a partially permeable membrane from a region of high to low concentration.
water potential - if a solution has a high water potential, high concentration.
watering a plant inc the water potential of the soil around it. all the water draws in water until turgid. the contents push against the cell wall - turgor pressure. no water in soil plant will wilt as cells become flaccid. doesn't lose shape due to inelastic cell wall, just droop.
blood
contains plasma, platelets, red blood cells and white blood cells.
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Red blood cells - carry oxygen, dot have nucleus, very flexible pass through capillaries
diffusion
Is the net movement of particles from an area of higher concentration to an area of lower concentration.
cell membranes - substances move in and out by diffusion. only very small like glucose, amino acids and water.
arteries - carry blood away from the heart. strong elastic,
veins - carry blood to heart, thin walls, big lumen, valves
capillaries - exchange of materials, tiny, carry blood close to every cell in the body to exchange. permeable walls so diffuse in and out.