Biochemistry > Membranes > Flashcards

Membranes Flashcards

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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
Carbohydrates attached to lipids in the membrane
Glycolipids
26
Carbohydrates attached to proteins in the membrane
Glycoproteins
27
Give a use of the diversity of molecule locations on the cell membrane
* Can be used as markers * Distinguish one cell from another
28
Give the most important monosaccharides of the membrane
* Glucose * Mannose * Galactose
29
Lipid raft structure
* Sphingolipid + Cholesterol rich * Tightly packed * Ordered assembly of specific proteins
30
Lipid raft function
* Membrane transport * Fluidity * Signal transduction * Neurotransmission
31
Caveolae
Grape-like clusters in the membrane
32
What causes an increase in membrane fluidity (elasticity)
* Increased temperature * Decreased cholesterol *(eukaryotes only)* * Increased proportion of cis-unsaturated fatty acids
33
Which molecules other than water can pass across the cell membrane by _simple diffusion_
* Oxygen * CO2 * Ammonia * Ethanol * Urea
34
What reduces the rate of diffusion from inside the cell to outside the cell?
Molecules running into the lipid bilayer of the membrane
35
Ions and charged molecules move...accross cell membranes
Poorly
36
Give examples of molecules which require facilitated diffusion to pass through a membrane
* Glucose * Chloride ions
37
Give the two major groups of integral membrane proteins
* Carrier molecules/transporters * E.g glucose transporters, carnitine, translocase * Hydrophilic pores * E.g aquaporin
38
Facilitated diffusion of glucose is responsible by...
**GLUT** *(Glucose* *transporter**)*
39
GLUT-1
RBCs, Brain ## Footnote *(Non-insulin dependent)*
40
GLUT-2
Intestinal epithelium, Liver, Kidney ## Footnote *(Could be partly insulin dependent)*
41
GLUT-3
Brain ## Footnote *(Non-insulin dependent)*
42
GLUT-4
Muscle, fatty acid ## Footnote *(insulin dependent)*
43
Give the stages of facilitated diffusion of glucose
1. Glucose binds to GLUT-1 2. Conformational change 3. Glucose moves to the interior 4. Glucose is released
44
Which molecules allow facilitated passive transport of fatty acids into mitochondria?
* Carnitine (carrier molecule) * Translocase (a transport protein) Form the 'carnitine shuttle'
45
Gibbs-Donnan-Equilibrium (Short summary)
Unequal ion distribution on both sides of the semipermeable membrane leads to _membrane potential_
46
Solution Equilibrium
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
Solution equilibrium in the presence of an impermeable anion e.g Pr-
* K+ and Cl- penetrate the membrane * Pr- is retained on side I
48
Gibbs-Donnan Equilibrium (Detailed summary)
* 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
Active transport
_Expenditure of metabolic energy_ to move ions or solutes across membranes _against their electrochemical gradient_.
50
Give the two types of active transport
* Primary active transport * Secondary active transport ## Footnote *Differ in source of energy*
51
Primary active transport Examples
* Transport protein that hydrolyses ATP * Na-K pump * Proton pump * ABC transporter protein family
52
Secondary active transport Examples
Transport across membranes by energy stored in _ion gradients_ SGLT-1 + SGLT-2 transporters
53
Give the use of Na/K pump
* Resting membrane potential * Driving force for secondary active transport * Osmotic gradient
54
What is the ratio of the number of ions transported by Na-K ATPase pump?
3Na+:2 K+
55
Give the process of Na/K ATPase pump
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
Describe the effects of Na/K ATPase pump inhibition in cardiac myocytes
1. Inhibition 2. Increase in IC [Ca2+] 3. Enhanced cardiac contractility
57
How can Na/K ATPase pump of cardiac myocytes be inhibited?
By cardiac glycosides Can be found in: * *Digitalis purpurea* * *Strophanthus* *gratus*
58
Where is the proton pump located?
* Respiratory chain * Epithelial cells of stomach mucous membrane (HCl secretion)
59
ABC transporter protein family
* ABC = **_A_**TP-**_B_**inding **_C_**assette * Multi-drug resistance (MDR) protein * Pump non-polar molecules (drugs) out of the cell * Drug resistance * Tumour cells have MDR
60
Cotransport
* Energy released during ions transport down an electrochemical gradient * used to pump ions/molecules up their electrochemical gradient
61
Cotransporter carrying both solutes in the same direction
Symport
62
Cotransporter carrying solutes in opposite directions
Antiport
63
SGLT-1
* Cotransport of Glucose and 2 sodium * Into small intestinal epithelial cell
64
SGLT-2
* Cotransport of Glucose and 2 sodium * Into tubular epithelial cells of the kidney
Biochemistry
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