plasma membranes and cell transport

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what is active transport?
the movement of molecules/ions into/out of the cell from lower conc to higher conc using energy and carrier molecules
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what is required for AT?
energy in the form of ATP > from respiration > requires oxygen
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how are molecules prevented from leaking back out of the cell?
by the barrier of the cell-surface membrane's bilayer
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what is AT limited by?
the availability of oxygen
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what enters/leaves cells by AT?
nitrate ions
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what is diffusion?
the net movement of substance from high conc to low conc until a dynamic equilibrium is reached
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what moves by diffusion?
CO2, O2, lipid soluble substances
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what is the rate of diffusion affected by?
conc gradient, SA, surface thickness
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how is it affected by the size/nature of the diffusing molecule?
-polar molecules diffuse faster than non-polar. -fat soluble diffuse faster than water soluble. -smaller molecules diffuse faster.
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what is facilitated diffusion?
the movement of a substance from a high conc to a low conc through a specific channel/carrier protein until equilibrium is reached.
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what moves by facilitated diffusion?
large, charged, water-soluble molecules e.g. glucose
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what does it rely on?
kinetic energy
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what do channel proteins line?
a water-filled pore in the membrane
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why?
so water-soluble molecules can easily pass through
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how do carrier proteins work?
the substance combines with the protein and is carried from one side of the membrane to the other and the proteins are specific to a particular substance
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what is osmosis?
the movement of water from high water potential to low water potential through a SPM until a dynamic equilibrium is reached
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what is water potential?
the pressure created by molecules
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how do you find the water potential of something?
place the tissue in a series of solutions with differing water potential, when there is no net gain/loss of water, then the water potential is the same as the external solution
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what do lipids contain?
carbon, hydrogen, oxygen
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are they soluble or insoluble in water?
insoluble
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what are the three groups?
phospholipids, waxes, triglycerides
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what are the roles of lipids?
-energy source. -waterproofing (insoluble in water). -insulation (low conductors of heat so retain body heat). -protection.
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describe the emulsion test.
homogenise sample in alcohol > add ice cold water > a milky emulsion indicates the presence of a lipid
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what makes up a triglyceride?
3 fatty acids and 1 glycerol molecule
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how is a triglyceride formed and what is the reaction catalysed by?
a condensation reaction and by lipase
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what are fatty acids?
long hydrocarbon chains
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what is there are no carbon-carbon double bonds?
it is saturated
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what if there is 1 double bond?
it is mono-unsaturated
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what if there is more than one double bond?
polyunsaturated
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what is the function of a phospholipid?
to contribute to the flexibility of the membrane and the transfer of lipid soluble substances along them
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what are they made up of?
they have a hydrophilic head which interacts with water but not fat and a hydrophilic tail which mixes with fat but orients away from water.
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what do they form on the cell surface membrane?
a bilayer sheet
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how are proteins arranged in the bilayer?
randomly but are either intrinsic or extrinsic
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describe extrinsic proteins
they are on the bilayer surface/partly embedded and give mechanical support to the membrane or act as cell receptors for hormones
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describe intrinsic proteins
they span the bilayer and act as carries to transport water-soluble molecules across the membranes / others are enzymes
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what are the functions of proteins?
-rovide structural support. -form ion channels to allow AT. -help cells adhere together
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what are the functions of the plasma membrane?
-selectively permeable barrier. -structural support. -recognition of substances. -communication with other cells. -allows mobility in some organisms
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Other cards in this set

Card 2

Front

what is required for AT?

Back

energy in the form of ATP > from respiration > requires oxygen

Card 3

Front

how are molecules prevented from leaking back out of the cell?

Back

Preview of the front of card 3

Card 4

Front

what is AT limited by?

Back

Preview of the front of card 4

Card 5

Front

what enters/leaves cells by AT?

Back

Preview of the front of card 5
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