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Biochemistry > Membranes > Flashcards

Membranes Flashcards

1
Q

Prokaryote

A

Cells without a nucleus

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2
Q

Eukaryote

A

Cells with a nucleus

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3
Q

Compositions of the cell membrane

A
  • 40% Lipid
  • 60% Protein
  • <1% Sugar moieties
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4
Q

Phospholipids with a glycerol backbone are called…

A

Glycerol phosphatides

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5
Q

Give two examples of glycerol phosphatides

A
  • Lecithine
  • Cephaline
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6
Q

What is shown?

A

Glycerol phosphatide: Lecithine

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7
Q
A

Choline

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8
Q
A

Phosphate

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9
Q
A

Polar head group

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10
Q
A

Glycerol backbone

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11
Q
A

Fatty acid chains

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12
Q

A glycerol phosphatide, with a cholamine molecule linked to it

A

Cephaline

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13
Q

Glycerol phosphatide without choline or cholamine

A

Phosphatidic acid

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14
Q

Sphingosine

A

Sphingolipid:

  • 18-carbon amino alcohol
  • Unsaturated hydrocarbon chain
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15
Q

Ceramide

A

Sphingolipid:

  • Sphingosine + fatty acid
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16
Q

Sphingomyelin structure

A

Ceramide + Phosphate + Choline

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17
Q

Unsaturated fatty acid

A
  • 1-3 double bonds along the hydrocarbon chain
  • Causes a kink in the chain shape
  • Results in looser packing + lower melting point
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18
Q

The function of cholesterol in the cell membrane

A

Helps stabilise the membrane

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19
Q

Give the movement of lipids in the membrane

A
  • Rotation
  • Lateral diffusion
  • Transversial diffusion
    • Flippase protein + energy needed
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20
Q

What are the two classes of membrane protein?

A
  • Integral protein
  • Peripheral protein
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21
Q

Integral proteins

A
  • Transmembrane proteins
  • Hydrophobic regions
  • Hydrophilic ends
  • Generally serve as ion channels
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22
Q

Peripheral proteins

A
  • Loosely bound to surface of the membrane
  • Static function
  • Receptor function
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23
Q

Cell surface receptor

A
  • Span cell membrane
  • Detect chemical signals outside the cell
  • Transmit these detections inside
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24
Q

Carbohydrates of the membrane are usually…

A
  • Branched oligosaccharides
  • <15 sugar units
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25
Q

Carbohydrates attached to lipids in the membrane

A

Glycolipids

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26
Q

Carbohydrates attached to proteins in the membrane

A

Glycoproteins

27
Q

Give a use of the diversity of molecule locations on the cell membrane

A
  • Can be used as markers
  • Distinguish one cell from another
28
Q

Give the most important monosaccharides of the membrane

A
  • Glucose
  • Mannose
  • Galactose
29
Q

Lipid raft structure

A
  • Sphingolipid + Cholesterol rich
  • Tightly packed
  • Ordered assembly of specific proteins
30
Q

Lipid raft function

A
  • Membrane transport
  • Fluidity
  • Signal transduction
  • Neurotransmission
31
Q

Caveolae

A

Grape-like clusters in the membrane

32
Q

What causes an increase in membrane fluidity (elasticity)

A
  • Increased temperature
  • Decreased cholesterol (eukaryotes only)
  • Increased proportion of cis-unsaturated fatty acids
33
Q

Which molecules other than water can pass across the cell membrane by simple diffusion

A
  • Oxygen
  • CO2
  • Ammonia
  • Ethanol
  • Urea
34
Q

What reduces the rate of diffusion from inside the cell to outside the cell?

A

Molecules running into the lipid bilayer of the membrane

35
Q

Ions and charged molecules move…accross cell membranes

36
Q

Give examples of molecules which require facilitated diffusion to pass through a membrane

A
  • Glucose
  • Chloride ions
37
Q

Give the two major groups of integral membrane proteins

A
  • Carrier molecules/transporters
    • E.g glucose transporters, carnitine, translocase
  • Hydrophilic pores
    • E.g aquaporin
38
Q

Facilitated diffusion of glucose is responsible by…

A

GLUT (Glucose transporter**)

39
Q

GLUT-1

A

RBCs, Brain

(Non-insulin dependent)

40
Q

GLUT-2

A

Intestinal epithelium, Liver, Kidney

(Could be partly insulin dependent)

41
Q

GLUT-3

A

Brain

(Non-insulin dependent)

42
Q

GLUT-4

A

Muscle, fatty acid

(insulin dependent)

43
Q

Give the stages of facilitated diffusion of glucose

A
  1. Glucose binds to GLUT-1
  2. Conformational change
  3. Glucose moves to the interior
  4. Glucose is released
44
Q

Which molecules allow facilitated passive transport of fatty acids into mitochondria?

A
  • Carnitine (carrier molecule)
  • Translocase (a transport protein)

Form the ‘carnitine shuttle’

45
Q

Gibbs-Donnan-Equilibrium (Short summary)

A

Unequal ion distribution on both sides of the semipermeable membrane leads to membrane potential

46
Q

Solution Equilibrium

A
  1. A semipermeable membrane forms 2 chambers
  2. KCl solution added to one chamber (I)
  3. Water added to the other chamber (II)
  4. K+ and Cl- ions passively diffuse through the membrane
  5. Ions diffuse from I to II until equilibrium
  6. Final solutions in each chamber contain equal K+ and Cl-
47
Q

Solution equilibrium in the presence of an impermeable anion e.g Pr-

A
  • K+ and Cl- penetrate the membrane
  • Pr- is retained on side I
48
Q

Gibbs-Donnan Equilibrium (Detailed summary)

A
  • Side I has K+ ions and Pr-
  • Side II has K+ and Cl- (Both permeable)
  • K+ equimolar on both sides
  • Cl- diffuses from II to I
  • Negative charge on side I
  • K+ attracted to side I but [K+] of side I exceeds that of side II
  • K+ moves from side I to side II along a concentration gradient
  • Membrane potential
49
Q

Active transport

A

Expenditure of metabolic energy to move ions or solutes across membranes against their electrochemical gradient.

50
Q

Give the two types of active transport

A
  • Primary active transport
  • Secondary active transport

Differ in source of energy

51
Q

Primary active transport

Examples

A
  • Transport protein that hydrolyses ATP
    • Na-K pump
    • Proton pump
    • ABC transporter protein family
52
Q

Secondary active transport

Examples

A

Transport across membranes by energy stored in ion gradients

SGLT-1 + SGLT-2 transporters

53
Q

Give the use of Na/K pump

A
  • Resting membrane potential
  • Driving force for secondary active transport
  • Osmotic gradient
54
Q

What is the ratio of the number of ions transported by Na-K ATPase pump?

55
Q

Give the process of Na/K ATPase pump

A
  1. High [Na+] in the cytoplasm
  2. ATP hydrolysed → Phosphorylation of cytoplasmic loop of the pump and release of ADP
  3. Na+ released
  4. Pump binds 2 EC K+ ions
  5. K+ ions released inside the cell
  6. Alpha subunits dephosphorylated
56
Q

Describe the effects of Na/K ATPase pump inhibition in cardiac myocytes

A
  1. Inhibition
  2. Increase in IC [Ca2+]
  3. Enhanced cardiac contractility
57
Q

How can Na/K ATPase pump of cardiac myocytes be inhibited?

A

By cardiac glycosides

Can be found in:

  • Digitalis purpurea
  • Strophanthus gratus
58
Q

Where is the proton pump located?

A
  • Respiratory chain
  • Epithelial cells of stomach mucous membrane (HCl secretion)
59
Q

ABC transporter protein family

A
  • ABC = ATP-Binding Cassette
  • Multi-drug resistance (MDR) protein
    • Pump non-polar molecules (drugs) out of the cell
      • Drug resistance
      • Tumour cells have MDR
60
Q

Cotransport

A
  • Energy released during ions transport down an electrochemical gradient
  • used to pump ions/molecules up their electrochemical gradient
61
Q

Cotransporter carrying both solutes in the same direction

62
Q

Cotransporter carrying solutes in opposite directions

63
Q

SGLT-1

A
  • Cotransport of Glucose and 2 sodium
  • Into small intestinal epithelial cell
64
Q

SGLT-2

A
  • Cotransport of Glucose and 2 sodium
  • Into tubular epithelial cells of the kidney

Biochemistry (21 decks)

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