theory of cell membrane structure - proteins embedded in a phospholipid bilayer
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glycolipid
lipid/phospholipid with a chain of carbohydrate molecules attached
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glycoprotein
protein with a chain of carbohydrate molecules attached
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plasma membrane functions
partially permeable. separates cell contents from surroundings. regulates transport of materials into/out of cell. has antigens (immune system recognises cell as 'self'). contains receptors for chemical signals - site for cell signalling
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phospholipid molecules' role in the plasma membrane
hydrophilic heads in contact with watery exterior/interior (cytoplasm) and hydrophobic tails in centre of membrane. lipids can swap places, giving fluidity.
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integral proteins
span the whole lipid bilayer, e.g. carrier/channel proteins
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peripheral proteins
don't span the whole lipid bilayer
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role of cholesterol in the plasma membrane
molecules fit between phospholipids and bind to tails so they pack closely together. makes membrane more rigid - stability
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glycocalyx
formed from carbohydrate chains attached to proteins or lipids in the membrane
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carrier proteins
change their shape to carry specific molecules across the membrane
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protein channels
have pores to allow specific ions to pass through
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diffusion
movement of molecules from an area of high to low concentration of that molecule down their concentration gradient. passive process
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facilitated diffusion
movement of molecules from an area of high to low concentration of that molecule across a PPM via protein channels or carriers. passive process
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aquaporins
specific water channel proteins found in membranes where a high rate of water movement is required, so water doesn't have to cross a lipid environment
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how is the concentration gradient maintained?
molecules enter cells, then pass into organelles and are used in metabolic reactions.
how does temperature affect rate of simple diffusion?
as temperature increases, molecules have more kinetic energy, so rate of diffusion increases.
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how does diffusion distance affect rate of simple diffusion?
the thicker the membrane to diffuse across, the slower the rate of diffusion
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how does surface area affect rate of simple diffusion?
more diffusion can take place across a larger surface area
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how does size of diffusion molecule affect rate of simple diffusion?
smaller ions/molecules diffuse quicker than larger ones
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how does concentration gradient affect rate of simple diffusion?
the steeper the gradient, the faster the diffusion down the concentration gradient
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osmosis
diffusion of water molecules down their water potential gradient, from an area of high to low water potential, across a PPM
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water potential
measure of the tendency of water molecules to diffuse from one area to another
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highest possible water potential
0kPa - pure water. lower water potential has a negative value
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cytolysis (/haemolysis)
animal cells swelling and bursting due to many water molecules entering - plasma membrane breaks
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turgidity
plant cell swells and pushes against the cell wall, which prevents further swelling and potential bursting
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crenation
animal cells shrivelling due to many water molecules moving out of the cell
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plasmolysis
plant cell's cytoplasm shrinks and membrane pulls away from the cell wall.
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active transport
movement of substances against their concentration gradient across a cell membrane, using ATP and carrier proteins
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endocytosis
bulk transport of molecules, too large to pass through a cell membrane even via channel or carrier proteins, into a cell
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exocytosis
bulk transport of molecules, too large to pass through a cell membrane even via channel or carrier proteins, out of a cell
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phagocytosis
solid matter ingested by endocytosis
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pinocytosis
liquid matter ingested by endocytosis
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effect of solvents on phospholipids
organic solvents damage cell membranes as they dissolve lipids
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Other cards in this set
Card 2
Front
lipid/phospholipid with a chain of carbohydrate molecules attached
Back
glycolipid
Card 3
Front
protein with a chain of carbohydrate molecules attached
Back
Card 4
Front
partially permeable. separates cell contents from surroundings. regulates transport of materials into/out of cell. has antigens (immune system recognises cell as 'self'). contains receptors for chemical signals - site for cell signalling
Back
Card 5
Front
hydrophilic heads in contact with watery exterior/interior (cytoplasm) and hydrophobic tails in centre of membrane. lipids can swap places, giving fluidity.
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