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Flashcards in membranes Deck (36)
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what are membranes made of

phospholids in bilayers


what is the head of a phodpholipid

polar (hydrophillic)


what is the tail of a phospholipid

non polar (hydrophobic)


what is the hydrophobic tail made of

fatty acids and lipids


what is the model of the cell membrane called

fluid mosaic model


how is the membrane fluid

some parts are not attached to any other part of the cell and so can move freely


why is the membrane described as mosaic

because of the different sizes of phospholipids proteins and cholestrol


what is the purpose of cholesterol in the membrane

makes membrane more rigid and stable


what is the purpose of the glycoproteins/lipids

act as hormone receptors or cell to cell proteins


what is an extrinsic protein

only in the half of the membrane which is hydrophillic


what is an intrinsic protein

through all of the membrane


how do small and non polar molecules get through the membrane

they diffuse through the lipid bilayer


how do other molecules get through the membrane

some are too big or polar and so can't go through the lipid bilayers, instead they go through hydrophillic channel or carrier proteins.


what is the difference between a channel protein and a carrier protein

channel - have a hydrophilic pore which can be open and closed carrier - have a binding shape for the molecule. they change their shape to allow the molecule to cross the membrane


what is diffusion

movement of molecules from an area of higher concentration to an area of lower concentration


what is osmosis

movement of water molecules from an area go high concentration of water to an area of low concentration of water through a partially permeable membrane


what is a solvent

a substance that a chemical can dissolve in


what is a solute

the molecule that dissolves


what is water potential

a measure of free energy of water molecules and the tendency of water to movw


what is water potential measured in

kPa (kilopascals)


water moves from a less negative.........

water potential to a more negative water potential


what is the water potential in a dilute solution

more water potential energy


what is the water potential in a concentrated solution

less water potential energy


what is solute potential

how easily water molecules move out of a solution the more solute present the tighter the water molecules are held


what is pressure potential

pressure builds up within a plant cell due to the cell wall making the plant turgid. this pressure is pressure potential, resisting more water entry


what is the sign (+ or -) of pressure potential



water potential =

pressure potential + solute potential


what does it mean in a cell is hypertonic (plant and animal)

(plant)it is plasmolyse, the cell membrane is pulling away from the cell wall (animal) it will crenate it means that to much water is leaving the cell when in a concentrated solution in order to balance the amount of water outside the cell to the amount of water inside the cell


what does is mean if a cell is isotonic

it remains the same as water leaves in equal parts


what does it mean if a cell is hypotonic (plant and animal)

there is more water outside the cell than there is inside so more water will try and enter but the pressure potential will increase (plant) the cell wall will push out making the cell turgid(animal) the cell will explode as it has no cell wall to protect it and cant cope with the pressure