transport across cell membranes

?
define diffusion
the net movement of particles down a concentration gradients through a semi-permeable membrane until the concentrations are equal
a passive process
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which substances can move via diffusion?
lipid-soluble molecules
e.g, h2o co2 and o2
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define facilitated diffusion
the net movement of particles down a concentration gradients through a semi-permeable membrane until the concentrations are equal using carrier or channel proteins
a passive process
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what is a channel protein?
it enables charged substances to diffuse across membranes whilst also controlling the movement
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what is a carrier protein?
have a binding site for a specific solute so it can be moved across a membrane
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how does temperature affect diffusion?
increases kinetic energy so particles move faster
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how does surface area affect diffusion?
more space for molecules to pass through so its faster
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how does concentration gradient affect diffusion?
a bigger difference in concentration increases the rate of diffusion
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how does thickness of the exchange surface affect diffusion?
the thinner the surface, the shorter the diffusion pathway so faster
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what is ficks law?
rate of diffusion= area of diffusion surface x difference in concentration / thickness of surface
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define osmosis
net movement of water particles down its water potential gradient from high water potential to low water potential until WP is equal
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what is an isotonic solution?
a solution that has an equal water potential to the inside of the cell
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what is a hypertonic solution?
solution that has a lower water potential to the inside of the cell
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what is a hypotonic solution?
solution that has a higher water potential to the inside of the cell
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define active transport?
movement of molecules against the concentration gradient from an area of low to high concentration using a specific carrier protein and ATP
this is an active process
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how does the co-transport of glucose and Na+ work?`
1. Na+ ions are actively transported into the cell to cause a concentration gradient
2. Na+ diffuses into the cell through the co-transporter protein, along with glucose
3. this increases concentration of glucose in a cell so glucose diffuses into the blo
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how do you calculate percentage change?
final mass-initial mass/initial mass x 100
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how do you calculate ratios?
final mass/ initial mass
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give 2 similarities in the movement of substances by diffusion and osmosis
both involve movement form high to low concentration
neither require energy from ATP
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explain the advantages of lipid droplet and micelle formation
droplets increase the surface area for enzyme action and faster hydrolysis, micelles transport fatty acids through membranes
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Putting bee honey on a cut kills bacteria. Honey contains a high concentration of
sugar.
Use your knowledge of water potential to suggest how putting honey on a cut kills
bacteria.
Water potential in bacterial cells higher than in honey so water leaves bacteria cells by osmosis which stops metabolic reactions.
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Other cards in this set

Card 2

Front

which substances can move via diffusion?

Back

lipid-soluble molecules
e.g, h2o co2 and o2

Card 3

Front

define facilitated diffusion

Back

Preview of the front of card 3

Card 4

Front

what is a channel protein?

Back

Preview of the front of card 4

Card 5

Front

what is a carrier protein?

Back

Preview of the front of card 5
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