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Key Concepts in Biology (Cells (Animal cells (Nucleus - contains genetic…
Key Concepts in Biology
Cells
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Plant cells
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Large vacuole - contains cell sap, a weak solution of sugar and salts. It maintains the internal pressure to support the cell.
Chloroplasts - these are where photosynthesis occurs, which makes food for the plant. They contain a green substance called chlorophyll.
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Animal cells
Nucleus - contains genetic material that controls the activities of the cell. Genetic material is arranged into chromosomes.
Cytoplasm - gel-like substance where most of the chemical reactions happen. It contains enzymes that control these chemical reactions.
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Mitochondria - these are where most of the reactions for respiration take place. Respiration transfers energy that the cell needs to work.
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Bacterial cells
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Plasmid DNA - small loops of extra DNA that aren't part of the chromosome. Plasmids contain genes for things like drug resistance, it can be passed between bacteria.
Flagellum - a long, hair-like structure that rotates to make the bacterium move. It can be used to move the bacteria away from harmful substances like toxins and towards beneficial things like nutrients or oxygen
Specialised Cells
Egg cells
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Straight after fertilisation, its membrane changes structure to stop any more sperm getting in. This makes sure the offspring end up with the right amount of DNA
Sperm cell
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It has lots of mitochondria in the middle section to provide the energy needed to swim this distance.
It also has an acrosome at the front of the head, where it stores the enzymes needed to digest its way through the membrane of the egg cell.
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Enzymes
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Enzymes can also do the opposite of these # # #
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Diffusion, Osmosis and Active Transport
Diffusion
Diffusion is the net (overall) movement of particles from an area of high concentration to an area of low concentration
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Osmosis
Osmosis is the net movement of water molecules across a partially permeable membrane from a region of higher water concentration to s region of lower water concentration
Active Transport
Active transport is the movement of particles across a membrane against a concentration gradient (e.g. from an area of lower concentration to an area of higher concentration) using energy transferred during respiration