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1st yr-Med 2022-2023 > MCB L2 > Flashcards

MCB L2 Flashcards

1
Q

State the function of plasma membranes

A

Enclose cell
Allows essential difference between cytosol + external environment
Impermeable - allows controlled access to inside cell

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2
Q

State the function of ion gradients across membranes

A

Synthesis of ATP
Transport of selected solutes
Transmission of electrical impulses

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3
Q

Descibe the structure of the cell membrane

A

Phospholipids
Proteins
(50:50)

Hydrophillic heads face outwards, hydrophobic tails face inwards

Creates a double bilayer - bimolecualr leaflet

Cell membranes are plastic + deformable + mobile

Fluid dynamic structure - lipid molecules move freely about the plane - rarely flip

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4
Q

Describe the function of proteins in cell membranes

A

Form structural links with cytoskeleton - cytoskelton anchors components of cell membrane and keeps membrane rigid

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5
Q

Describe the structure of phospholipids

A

Phosphate head - choline group linked to glycerol group via phosphate group

TWO hydrocarbon hydrophobic fatty acid tails
One tail = fully saturated (straight) One tail = unsaturated (1/ more cis double bond, giving it a kinked profile)

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6
Q

State the structural significance of one of the hydrocarbon fatty acid chains of the phospholipid having a “kinked” profile

A

Prevents phospholipids from becoming too closely packed together

Allows fluid dynamic membrane

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7
Q

Describe the formation of liposomes

A

Type of spherical vesicle

  • Phospholipids placed in water, phospholipids aggregate (automatically arrange themselves) into bimolecular sheets - double bilayer of phospolipids where hydrophobic fatty acid tails are facing inwards away from water and the hydrophillic heads are facing towards the water
  • Liposomes formed, separates the two aqueous phases
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8
Q

Why do we have charge assymetry?

A

Different components inside and outside membranes, therefore, charge assymetry

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9
Q

State 3 enzymes involved in mantaining membrane assymetry

A
  1. Flipases
  2. Flopases
  3. Scramblases
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10
Q

State the function of flippases

A

Transfer / move / “flip” phospholipids from inner lumen to outer side / cystolic side of membrane

Specific flippases for specific phospholipids

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11
Q

State the function of floppases

A

Transfer / move / “flip” phosphollipids from outer sode / cystolic side of membrane to inner lumen

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12
Q

State the function of scramblases

A

Ensure equal number of phospholipids on both sides of bilayer by random transfer of phospholipids between each monolayer (inner layer and outer layer)

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13
Q

Diagram showing enzymes maintainining membrane assymetry

A

RECOGNISE FUNCTIONS OF:

  1. Flippase
  2. Floppase
  3. Scramblase
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14
Q

Breifly describe the structure of glycolipids

A

Sugar containing lipid molecule

Sugar group orientated towards outside of cell

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15
Q

State the function of gangliosides

A

Type of glycolipid
Has attached oligosachharides
Important role in surface of nerve cells
Ganglioside Gm1 - acts as surface receptor to bacterial toxin which causes cholera

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16
Q

State the function of cholestrol in membranes

A

Found in eukaryotic plasma membranes only

Oriente / fit between phospholipids in bilayer, hydroxyl heads of cholestrol are close to polar head groups of phosholipids
‘
PARTIALLY IMOBILISING PHOSPHOLIPID MOLECULES This leads to membrane becoming more rigid, less fluid, less permeable, less deformable

(ACTS AS A SPACER) Prevents phase transitioning in membranes - prevents membrane from freezing

17
Q

State 2 factors which affect the fluidity of the phospholipid membrane

A
  1. Fatty acid chain length - shorter fatty acid chain length means the chains are less likey to interact with each other, more fluidity
  2. Cis double bonds - higher number of cis bonds = more kinks = phospholipids less closely packed, more cholestrol can fit “snugly” in between - membrane spacer - preventing phase transitions (prevents membranes from freezing), allowing membranes to be fluid at lower temperatures
18
Q

What is glycocalyx?

A

Carbohyrdate rich zone on surface of cell
Consists of

Glycolipids
Oligosaccharides

19
Q

Selectins

A

Proteins that bind to the cell surface and mediate cell-cell adhesions

Provide surface markers used to identify certain cells

20
Q

State 4 membrane proteins and their functions

A

Transporters: transport ions, metabolites, nutrients

Anchors: Anchor membrane to macromolecules

Receptors: Detect external signals

Enzymes: Carry out specific reactions

21
Q

State 2 membrane proteins found in red blood cell membranes and their functions

A

Spectrin - cytoplasmic side of membrane
Ankyrin - inner side of membrane - links ankyrin to transmembrane proteins

BOTH - give RBC characteristic shape

22
Q

State 4 protein-membrane associations

A

Transmembrane

Lipid-linked

Protein attached

Monolayer associated

1st yr-Med 2022-2023 (57 decks)

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