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Biology Year 12 > Transport across membranes (4) > Flashcards

Transport across membranes (4) Flashcards

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1
Q

What is meant by ‘fluid’ in the fluid mosaic model of membranes?

A

phospholipid bilayer in which individual phospholipids can move causing membrane to have a flexible shape

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2
Q

What is meant by ‘mosaic’ in the fluid mosaic model of membranes?

A

extrinsic and intrinsic proteins of different sizes and shapes are embedded

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3
Q

What is the role of cholesterol in membranes?

A

steroid molecule in some plasma membranes which connects phospholipids and reduces fluidity to make bilayer more stable

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4
Q

What is the role of glycolipids in membranes?

A

cell signalling and cell recognition

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5
Q

What do extrinsic proteins contain?

A

binding sites/receptors
antigens (glycoproteins)

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6
Q

What are the 2 functions of extrinsic proteins in membranes?

A
  • bind cells together
  • involved in cell signalling
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7
Q

What do intrinsic proteins contain and what are these for?

A
  • electron carriers (for respiration and photosynthesis)
  • channel proteins (facilitated diffusion)
  • carrier proteins (active transport/facilitated diffusion)
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8
Q

What are the 4 functions of a membrane?

A
  • provide internal transport system
  • selectively permeable to regulate passage of molecules into/out of organelles
  • provide reaction surface
  • isolate organelles from cytoplasm for specific metabolic reactions
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9
Q

What are the 3 functions of a cell-surface membrane?

A
  • isolates cytoplasm from extracellular environment
  • selectively permeable to regulate transport of substances
  • involved in cell signalling/cell recognition
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10
Q

What are 3 factors affecting membrane permeability?

A

1) temperature
2) pH
3) use of solvent

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11
Q

How does temperature affect membrane permeability?

A

high temperature denatures membrane proteins and phospholipid molecules have more kinetic energy and move further apart

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12
Q

How does pH affect membrane permeability?

A

changes tertiary structure of membrane proteins

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13
Q

How does the use of a solvent affect membrane permeability?

A

may dissolve membrane

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14
Q

What are the 4 steps on how colorimetry can be used to investigate membrane permeability?

A

1) use plant tissue with soluble pigment in vacuole (tonoplast cell-surface membrane disrupted, increasing permeability so pigment diffuses into solution)
2) select colorimeter filter with complementary colour
3) use distilled water to set colorimeter to 0 and measure the absorbance/% transmission value of the solution
4) high absorbance/low transmission means there is more pigment in the solution

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15
Q

What is meant by osmosis?

A

water diffuses across semi-permeable membranes from an are of higher water potential to an area of lower water potential, until a dynamic equilibrium is established

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16
Q

What is water potential?

A

pressure created by water molecules

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17
Q

What are the units for water potential?

A

kPa

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18
Q

What is the water potential of pure water at 25°C and 100kPa?

A

0

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19
Q

What 3 conditions are required for water potential to = 0

A

pure water
25°C
100kPa

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20
Q

What happens to water potential if there is more solute?

A

water potential becomes more negative

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21
Q

When does water potential become more negative?

A

when there is more solute

22
Q

What is the equation for volume of stock solution?

A

require concentration x final volume needed
________________________
concentration of stock solution

23
Q

What is the equation for volume of distilled water?

A

final volume needed - volume of stock solution

24
Q

What happens to plants when osmosis into cells occurs?

A

protoplast swells so cell becomes turgid

25
Q

What happens to animals when osmosis into cells occurs?

A

lysis of cells

26
Q

What happens to plants when osmosis out of cells occurs?

A

protoplast shrinks so cell becomes flaccid

27
Q

What happens to animals when osmosis out of cells occurs?

A

crenation of cells

28
Q

What is meant by a passive process?

A

process which requires no energy from ATP hydrolysis

29
Q

What is meant by simple diffusion?

A

net movement of small, lipid-soluble molecules directly through the bilayer from an are of high concentration to an area of lower concentration, down a concentration gradient

30
Q

What type of process is simple diffusion?

A

passive process

31
Q

What is meant by facilitated diffusion?

A

specific channel or carrier proteins with complementary binding sites transport large and/or polar molecules/ions that are no soluble in the hydrophobic phospholipid tail, down a concentration gradient

32
Q

What type of process is facilitated diffusion?

A

passive process

33
Q

What 2 types of diffusion are passive processes?

A

simple diffusion
facilitated diffusion

34
Q

How do channel proteins work?

A

hydrophilic channels bind to specific ions, causing one side of the protein to close and the other to open

35
Q

How do carrier proteins work?

A

binds to complementary molecule causing conformational change which releases molecule on other side of membrane

36
Q

Why is active transport not a passive process?

A

requires energy from ATP

37
Q

What are 5 factors affecting diffusion rate?

A

1) temperature
2) diffusion distance
3) surface area
4) size of molecule
5) difference in concentration

38
Q

What are 2 cell adaptations which max rate of transport across membranes?

A
  • many carrier/channel proteins
  • folded membrane to increase SA
39
Q

What is meant by active transport?

A

ATP hydrolysis releases phosphate group that binds to carrier protein, causing it to change shape so specific carrier proteins transport molecules/ions from area of low concentration to area of high concentration, against a concentration gradient

40
Q

What is the shape of a graph for simple diffusion?

A

straight diagonal line where rate of diffusion increases proportionally as concentration increases

41
Q

What is on the x and y axis of a graph showing simple or facilitated diffusion?

A

x-axis = concentration
y-axis = rate

42
Q

What is the shape of a graph for facilitated diffusion?

A

straight diagonal line that later levels off when all channel/carrier proteins are saturated

43
Q

What is one similarity between active transport and facilitated diffusion?

A

both may involve carrier proteins

44
Q

What are 2 differences between active transport and facilitated diffusion?

A
  • facilitated diffusion may also involve channel proteins
  • active transport requires energy from ATP hydrolysis whereas facilitated diffusion is a passive process
45
Q

What is meant by co-transport?

A

movement of a substance against its concentration gradient is coupled with the movement of another substance down its concentration/electrochemical gradient

46
Q

What are 2 types of intrinsic protein?

A

symport
antiport

47
Q

How do symport intrinsic proteins work?

A

transport substances in same direction

48
Q

How do antiport intrinsic proteins work?

A

transports substances in opposite direction

49
Q

What is an example of antiport intrinsic proteins at work?

A

sodium-potassium pump

50
Q

What happens to substances in co-transport?

A

bind to complementary intrinsic proteins

51
Q

What are 3 ways co-transport is involved in absorption of glucose/amino acids in the small intestine?

A
  • sodium ions are actively transported out of epithelial cells and into the bloodstream
  • sodium ion concentration is lower in epithelial cells than in the lumen of the gut
  • transport of glucose/amino acids from lumen to epithelial cells is coupled to facilitated diffusion of sodium ions down electrochemical gradient

Biology Year 12 (22 decks)

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