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Biology - mr ellis > module 2 - 5.1 structure and function of membranes > Flashcards

module 2 - 5.1 structure and function of membranes Flashcards

1
Q

what does the structure of plasma membranes allow?

A

allows cells to communicate with each other

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2
Q

what are the 2 types of membranes?

A
  • cell membranes
  • cell surface membranes/ plasma membranes
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3
Q

what holds a cell together?

A

cytoskeleton

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4
Q

which atom is on the end of a fatty acid tail?

A

oxygen

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5
Q

what is compartmentalisation?

A

formation of separate membrane-bound areas in a cell

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6
Q

what does compartmentalisation allow for the cell?

A
  • allows different environmental conditions in different parts of the cell
  • allows chemical conc. gradient to be made
  • allows protection of cellular components
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7
Q

what does a proton pump do inside a membrane?

A

makes it acidic

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8
Q

what are membranes?

A

flexible fluid able to break and fuse easily

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9
Q

what are the roles of the cell surface membrane?

A
  • environment
  • transport
  • cell to cell signalling
  • cell to cell joining
  • detection of changes in environment
  • site of chemical reactions
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10
Q

what does the environment provide for the cell?

A

provides fixed conditions inside cell cytosol (cytoplasm)

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11
Q

what does transport do for the cell?

A

provides partially permeable membrane that creates a barrier to some substances, controlling transport of substances in and out of cell

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12
Q

what does cell to cell signalling do for the cell?

A

has proteins (glycoproteins or lipiproteins) on it which interact with other cells

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13
Q

what is signal transduction?

A

process of cells responding to substances outside the cell

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14
Q

what does signal transduction do?

A

detects changes in environment

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15
Q

what do enzymes act as in the membrane?

A
  • site of chemical reactions for the cell
  • some proteins in the membrane may be enzymes
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16
Q

what does cell to cell joining allow the cell to do?

A

tissue formation

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17
Q

is the head of the phospholipid hydrophilic of hydrophobic?

A

hydrophilic

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18
Q

what is the hydrophilic head made up of?

A
  • phosphate group
  • phosphoester bond
  • glycerol
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19
Q

is the tail of the phospholipid hydrophilic of hydrophobic?

A

hydrophobic

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20
Q

what is the hydrophobic tail made up of?

A
  • ester bond
  • fatty acid
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21
Q

how are the fatty acid tails positioned?

A

towards each other they do not overlap e.g.
o==o
o==o
o==o

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22
Q

what is the structure of a phospholipid?

A
  • has a polar head (made of a glycerol and phosphate molecule)
  • has 2 fatty acid non-polar tails
  • they are amphipathic
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23
Q

what is the arrangement of a phospholipid?

A
  • spontaneously arranged into a bilayer
  • hydrophobic tails face inwards, surrounding polar fluids
  • 2 hydrophilic heads face outwards, touching extracellular fluids
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24
Q

when do phospholipids form micelles?

A

when submerged in water

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25
Q

why is a phospholipid amphipathic?

A

because phospholipids have hydrophilic and lipophilic regions

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26
Q

what does trilaminar mean?

A

it has 3 layers

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27
Q

which model was proposed by Seymour Singer and Garth Nicolson?

A

fluid-mosaic model

28
Q

how is a membrane fluid?

A
  • phospholipids create a viscous (sticky) layer but are free to move within it, relative to each other
  • proteins with varying size, shape and position were distributed throughout
29
Q

how can proteins move in the fluid mosaic model?

A

freely through the bilayer

30
Q

what is the ease of the movement of proteins dependent on?

A

the number of phospholipids with unsaturated fatty acids

31
Q

what do hydrophobic/ hydrophilic layers do?

A

restrict entry and exit of substances

32
Q

when is a phospholipid more fluid?

A

phospholipids with short or unsaturated fatty acids

33
Q

how can phospholipids move?

A

horizontally

34
Q

how do phospholipids from a bilayer in plasma membranes?

A
  • phospholipids have a polar phosphate group (hydrophobic) that face aq solutions
  • fatty acid tails are non-polar, repelled from aq environment
  • tissue fluid and cytoplasm are aqueous, phospholipids form 2 layers with hydrophobic tails facing inwards
  • hydrophobic phosphate groups face outwards, interact with aq environment by hydrogen bonding
35
Q

what are intrinsic/ integral proteins?

A

within the membrane

36
Q

what type of proteins are intrinsic/ integral proteins?

A

transmembrane proteins

37
Q

what are 2 large groups of transmembrane proteins?

A

channel proteins
carrier proteins

38
Q

what are channel proteins involved in?

A

facilitated diffusion

39
Q

what are carrier proteins involved in?

A

active transport

40
Q

where are extrinsic/ peripheral proteins present?

A

only one side of the membrane

41
Q

what do extrinsic/ peripheral proteins often have?

A

amino acids with hydrophilic R groups on the outer surface

42
Q

what will the amino acids on outer surface of the extrinsic protein bind to?

A

phospholipid heads or a transmembrane protein

43
Q

what are glycoproteins?

A

proteins containing oligosaccharide chains, covalently attached to amino acid R groups

44
Q

are the polar hydrophilic heads water soluble or water insoluble?

A

water soluble

45
Q

are the hydrophobic tails water soluble or water insoluble?

A

water insoluble

46
Q

what is the process called when the oligosaccharide chains covalently attach to amino acid R group?

A

glycosylation

47
Q

what can glycoproteins be found as?

A

intrinsic or transmembrane proteins

48
Q

what are the functions of glycoproteins?

A
  • CELL ADHESION - by tight junctions with proteins: claudin, occluding
  • CELL SIGNALLING - e.g receptor proteins for neurotransmitters, hormones and drugs
49
Q

what are glucolipids?

A

lipids with monosaccharide or oligosaccharide bound to the lipid

50
Q

what does oligo- mean?

A

more than di- and tri- but not as many as poly-

51
Q

what is the phosphate group in a phospholipid replaced by?

A

the sugar residue

52
Q

what are the functions of glycolipids in membranes?

A
  • CELL SURFACE MARKERS for cell to cell signalling
  • IMMUNE RESPONSES by acting as antigens (recognition of host cells by viruses)
  • ABO BLOOD GROUPS: the 4 main blood types (A, B, AB, O)
53
Q

what happens during cell to cell signalling?

A

the saccharide of the glycolipid binds to a specific complementary carbohydrate or carbohydrate-binding protein of a neighboring cell

54
Q

what are blood types determined by?

A

by the oligosaccharide attached to a specific glycolipid on the surface of red blood cells (acts as an antigen)

55
Q

what is cholesterol?

A

a sterol or modified steriod or type of lipid

56
Q

what is cholesterol biosynthesized by?

A

all animal cells

57
Q

what does cholesterol serve as?

A

something that comes before the biosynthesis of steroid hormones, bile acid, and vitamin D

58
Q

what is cholesterol required for?

A

build and maintain membranes and modulate membrane fluidity

59
Q

what does the hydroxyl group of each cholesterol molecule interact with?

A

water surrounding the membrane
(while the bulky steroid and hydrocarbon chain are embedded in the membrane, alongside non-polar fatty acid chains of the other phospholipid)

60
Q

cholesterol increases membrane packing, what does this do to the membrane?

A

alters membrane fluidity and maintains membrane integrity so that animal cells don’t need cell walls

61
Q

what do some transmembrane proteins act as?

A

enzymes

62
Q

what are many of the enzymes involved in respiration located as?

A

transmembrane proteins in the inner mitochondrial membrane

63
Q

what happens when the formation of ATP from ADP = Pi is energetically unfavourable?

A

proceed to happen in opposite direction

64
Q

how do you overcome the formation of ATP from happening in reverse?

A

ATP synthase couples with ATP synthesis to an electrochemical gradient

65
Q

what is the electrochemical gradient created by?

A

the difference in proton (H+) concentration across the inner mitochondrial membrane

66
Q

what happens during photosynthesis in plants (in terms of ATP)?

A

ATP is synthesized by ATP synthase using a proton gradient

67
Q

what is a proton gradient created in?

A

thylakoid lumen through thylakoid membrane and into the chloroplast stroma

Biology - mr ellis (76 decks)

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