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Biology eduquas > cell membranes and transport > Flashcards

cell membranes and transport Flashcards

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1
Q

components of cell membranes

A
  • phospholipids
  • protein (extrinsic, intrinsic)
  • glycoproteins
  • glycolipids
  • cholestorol
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2
Q

structure of phospholipid bilayer

A
  • inner layer = hydrophilic heads pointing towards the cell, touches cell cytoplasm
  • outer layer = hydrophilic heads point outwards, touch water surrounding cell
  • membrane centre = hydrophobic tails face each other
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3
Q

what does the phospholipid bilayer allow through

A
  • lipid soluble molecules
  • small un polar molecules
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4
Q

extrinsic proteins in phospholipid bilyer

A
  • partially span membrane
  • structural support
  • form recognition sites to identify cells
  • receptor sites of hormone attachment
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5
Q

intrinsic proteins in phospholipid bilayer

A
  • span both layers
  • carriers transport water soluble substances across
  • allow AT of ions by forming channels
    carrier or channel
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6
Q

function of glycoproteins and glycolipids in phospholipid bilayer

A
  • hormone receptors
  • cell-to-cell recognition
  • cell adhesion
  • in outer layer
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7
Q

function of cholesterol in phospholipid bilayer

A
  • only in animal cells
  • provide rigidity and stability
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8
Q

what is the glycocalyx on phospholipid bilayer

A
  • extracellular surface of glycosylated proteins
  • acts as a barrier
  • provides protection
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9
Q

what is the fluid mosaic model

A
  • fluid; individual phospholipids can move relative to each other
  • mosaic; proteins embedded vary in shape, size, pattern
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10
Q

what is the phospholipid bilayer permeable to

A
  • it is selectively permeable
  • lipid soluble substances (Vit A) and dissolved molecules (O2, CO2) dissolve and move directly through
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11
Q

factors that increase the permeability of cell membranes

A
  • temperature
  • organic solvents
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12
Q

how does temp increase cell membrane permability

A
  • above 40c
  • increase vibrations of phospholipids
  • they move further apart
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13
Q

how do organic solvents increase membrane permeability

A
  • they dissolve phospholipids
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14
Q

what is the phospholipid bilayer not permeable to

A
  • water soluble substances (ions, glucose, polar molecules) can’t pass through hydrophobic fatty acid tails
  • must use intrinsic proteins
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15
Q

what is ficks law?

A

diffusion rate =
SA times difference in concentration
divided by
length of diffusion pathway

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16
Q

what is a channel protein?

A
  • pores lined with polar (hydrophilic) groups
  • allows charged ions through
  • for diffusion and FD
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17
Q

what is a carrier protein?

A
  • allows large, polar molecules through
    e.g. water soluble, amino acids
  • molecule binds and the protein changes shape
  • for FD, AT
  • intrinsic
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18
Q

what is simple diffusion?

A

the movement of molecules from a region of high conc to low conc, down a conc gradient
- passive process (respiratory inhibitors have no effect)
- occurs through phospholipid bilayer

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19
Q

what is the diffusion rate increased by?

A
  • higher conc gradient
  • thinner membrane / shorter diffusion distance
  • larger SA
  • more pores in membrane
  • smaller molecules
  • being non-polar (fat-soluble)
  • increased temperature
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20
Q

what is facilitated diffusion

A

process of diffusion for polar molecules that can’t directly pass through the phospholipid bilayer
- using protein channels / carriers
- eventually reaches a max rate due to limiting number of channels
- not affected by respiratory inhibitors
- passive

21
Q

what is co-transport

A
  • a type of FD where 2 different substances use the same carrier protein at the same time
22
Q

stages of co-transport; when absorbing Na+ and glucose into blood and kidney nephron

A
  • 1 glucose molecule, 2 Na+ bind to carrier protein, outside of cell
  • protein changes shape. deposits them inside cell
  • they diffuse separately through the cell
  • reach other side. glucose enters blood by FD
  • 2 Na+ carried out epithelial cell by AT. K+ ions move in on same carrier
  • Na+ conc is always low in epithelial cell = brings more glucose in
    (glucose moves against conc gradient)
23
Q

what is active transport?

A

movement of molecules against conc gradient
requires energy from ATP from respiration

24
Q

role of ATP in AT

A

ATP activates carrier proteins to move molecule across the cell membrane
- used to transport molecules across

25
Q

evidence that AT and respiration are linked

A
  • AT relies on ATP
  • respiratory inhibitors (cyanide) or a lack of O2, prevents transport as no ATP is available
26
Q

types of bulk transport

A
  • endocytosis; phagocytosis, pinocytosis
  • exocytosis (secretion)
27
Q

what is endocytosis?

A

the active process of the cell membrane using extensions and cytoplasm to engulf material by putting it into vesicles

28
Q

process of phagocytosis

A
  • the uptake of solid material
  • engulfed, packed into vesicle
  • lysosome fuses with vesicles, enzymes digest the cell
  • products absorbed into cytoplasm
29
Q

process of pinocytosis

A
  • uptake of liquids
  • cell membrane folds inwards, surrounding liquid droplet
  • engulfs material
  • fuses together forming a vesicle
  • vesicle enters cell
30
Q

why does bulk transport require ATP

A

energy is needed for the cell membrane to move

31
Q

process of exocytosis

A
  • vesicle from golgi body moves to cell membrane
  • vesicle fuses with cell membrane
  • empties contents, releasing molecules
32
Q

what is osmosis

A

diffusion of water, from a region of high water potential to low water potential across a selectively permeable membrane

33
Q

what is water potential

A

the tendency of water molecules to move
- solute potential + pressure potential
- measure in kPa (kiloPascals)
- always negative
- 0 in pure water
- becomes more negative as conc of solution increases

34
Q

what is solute potential

A

the osmotic strength of a solution
- always negative (or 0 - pure water)
- when more solute is dissolved, there are fewer free water molecules so their KE reduces

35
Q

what is pressure potential

A

the outward pushing force of water in a vacuole against a cell wall
- positive or negative

36
Q

dilute solution meaning

A

higher water potential
less solute dissolved

37
Q

concentrated solution meaning

A

lower water potential
- water weakly bonded to solute = fewer free to move = lower KE

38
Q

what are turgid cells (plants)

A

in hypotonic solutions (fewer solutes / dilute) cells take up water by osmosis
- pressure potential increases as cytoplasm pushes on cell wall
swollen
- provides support = maintains shape

39
Q

what is incipient plasmolysis

A

cell has lost enough water for the cell membrane to begin drawing away from the cell wall
- pressure potential is 0

40
Q

what are plasmolysed cells?

A

cells in hypertonic (more concentrated) solutions become flaccid, cytoplasm/cell membrane retract from cell wall
water leaves the cell by osmosis
causes plants to wilt

41
Q

what solution must animal cells be in and why

A

isotonic
they lack a cell wall

42
Q

animal cells in a hypotonic solution

A

they burst
haemolysis occurs
e.g. in distilled water

43
Q

animal cells in hypertonic solution

A

they shrink
become crenated
e.g. salt solution

44
Q

what is tonicity?

A

the concentration of solutes

45
Q

hypertonic solution meaning

A

higher concentration of solute than cell
lower water potential

46
Q

hypotonic solution meaning

A

lower concentration of solute than cell
higher water potential

47
Q

isotonic solution meaning

A

same concentration of solute
same water potential
no net movement of water between solutions

48
Q

describe how secretory vesicles are produced and how digestive enzymes are secreted from the cell. (3)

A
  • golgi body packages enzymes into vesicles
  • vesicles move to cell membrane and fuse together
  • release contents outside cell by exocytosis
49
Q

how is the concentration gradient of sodium ions maintained while allowing glucose in? (4)

A
  • sodium-potassium pump transports Na+ out of epithelial cell into bloodstream
  • by active transport
  • reduces conc. of Na+ in cytoplasm of epithelial cell
  • high Na+ conc in lumen from dietary sources
  • co-transport of glucose with Na+ ions from lumen of small intestine

Biology eduquas (11 decks)

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