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Biochemistry > 1 - BM > Flashcards

1 - BM Flashcards

1
Q

Is lipid composition the major determinant of membrane thickness? Transition temperature?

A

Membrane thickness - No, protein composition.

Transition temp - yes, lipid composition.

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2
Q

Membrane fluidity is dependent on these two factors? How?

A

Lipid composition - longer and more saturated -> higher transition temp

Temp:
low temp -> paracrystalline state
high temp ->liquid-disordered or fluid state
intermediate temp -> liquid-ordered state (little thermal motion in the acyl chains of bilayer)

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3
Q

How to equalize the concentration across the membrane?

A
  1. binding of substance to a macromolecule
  2. maintaining a membrane potential
  3. coupling transport to an exergonic proces
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4
Q

How to equalize the concentration across the membrane?

A
  1. binding of substance to a macromolecule
  2. maintaining a membrane potential
  3. coupling transport to an exergonic proces
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5
Q

Catalysis

A

required by transbilayer movement of lipids

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6
Q

3 types of lipid aggregates

A
  1. Micelles - formation depends on the temperature, mixture of lipids and ratio of lipids; impt in intestinal digestion and absorption of lipids
  2. Bilayer - two lipid monolayers/leaflets forming a 2D sheet, relatively unstable and spontaneously form liposomes
  3. Liposome - When bilayer folds back on itself to form vesicle; can entrap; used as drug carrier and vectors of gene therapy
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7
Q

Three common types of membrane receptors?

A

> GPCR
RTK
Ion channel receptors

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8
Q

What are the different solute transport processes? Limitations? Similarities?

A
  1. Passive Transport (Diffusion, Facilitated Diffusion)
    - Limitations: thermal agitation, concentration gradient, solubility
  2. Active Transport (Primary, Secondary)
Active and Facilitated Diffusion:
> w/ specific binding sites
> carrier is saturable
> binding constant (Km)
> structurally similar
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9
Q

Are ion channels selective for one ion?

A

Yes, highly selective but there are also a few which are nonselective.

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10
Q

What are aquaporins?

A

Water channels that function as tetramers of identical monomers

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11
Q

Membrane-microdomains of lipid protein complexes?

A
  1. Lipid rafts
  2. Caveolae
  3. Tight junctions
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12
Q

What are biological membranes?

  • Covalent or non covalent assemblies?
  • thermodynamically stable or not? How about metabolically?
A

Char: Highly fluid, dynamic viscous, plastic structures

Fxns:

  • Divide cells into discrete compartments
  • Define cellular boundaries
  • Selective permeability (thus, maintaining differences from inside to outside of cell & free energy to be stored in concentration gradients)
  • Establishes order
  • Signal reception
  • Regulate molecular traffic
  • non covalent assemblies that are thermodynamically stable and metabolically active
  • For cell recognition
  • Maintain cell shape and locomotion
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13
Q

Fundamental properties of all biological membranes?

  1. Which is more dense -inner or outer layer?
  3. Movement of molecule based on permeability?
  4. Thickness and width of interface?
  5. What does it look like at xs?
A
  1. Dense inner layer than outer
  2. Dynamic
  3. Impermeable: most polar or charged
    Permeable: non polar compounds
  4. 7-10 nm thick; 1.5 nm interface
  5. Trilaminar
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14
Q

Basic structural unit of a biological membrane

A

Lipid bilayer

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15
Q

Major components of all membranes? Only organelle different?

A

Lipid and Proteins

> Inner mitochondrial membrane has higher protein component than lipid

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16
Q

Major lipids in mammalian membranes?

A
  1. Glycerophospholipids/Phosphoglycerides
  2. Sphingolipids
  3. Cholesterol
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17
Q

Structure of phosphoglycerides?

A

Glycerol molecule

+ phosphate esterified at the alpha-carbon

+ 2 long FA chains in ester linkages

+ Phosphorylated alcohol

*amphipathic

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18
Q

PPL are more abundant in which part of the membrane?

  1. Phosphatidylethanolamine
  2. -choline
  3. -serine
  4. -inositol
  5. Sphingomyelin
A
  1. Inner
  2. Outer
  3. Inner
  4. Inner
  5. Outer
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19
Q

Only membrane with more lipids than protein?

A

Myelin sheath

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20
Q

What are glycosphingolipids?

A

Sugar containing lipids built on a backbone of ceramide

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21
Q

Which phospholipid?
1. Major plasma membrane PPL in most cell types?

  1. Most variable PPL?
  2. Transfer of information from hormones and NTs across and found at the inner membrane
  3. Has net (-) which contributes to membrane potential; is important for binding
A
  1. Phosphatidylcholine
  2. Glycosphingolipids
  3. Phosphatidylinositol
  4. Phosphatidylserine
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22
Q

Sterols:

  1. Most common
  2. Location
  3. Characteristic
  4. Function
A
  1. Cholesterol
  2. Resides mainly at Plasma Membrane of mammalian cells
  3. Compact, rigid C8-branched HC chain attached to a D ring
  4. Reduces permeability and prevents packing up too closely
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23
Q

What is a glycocalyx?

A

CHO short (hydrophilic) chains at the ext surface of some proteins and lipids on the plasma membrane extending to the aq medium

Function: recognition molecules to protect cell from digestion and restricts uptake of hydrophobic compounds

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24
Q

Diffusion within the plane of membrane

A

Lateral diffusion

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25
Q

50% of the protein component in myelin? What is it?

A

Proteolipids

-hydrophobic lipoproteins soluble in Cf and mEtOH; insol in aq systems

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26
Q

Major lipoprotein in of brain myelin

A

Lipophilin

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27
Q

What maintains asymmety in membrane?

A

Lipid Transporters

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28
Q

Flippase vs Floppase vs. Scramblase

A

FlIppaSE

  • Specific for PPLserine and PPLethanolamine;
  • from extra to intra
  • ATP dependent

FlOppase

  • Not specific for PPL
  • ATP dependent

Scramblase

  • random; bidir
  • nonspecific
  • not ATP dependent. Instead, simulated by increase in intracellular calcium
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29
Q

Integral proteins are removable by what?

A

Detergents because they interfere with hydrophobic interactions

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30
Q

Integral Proteins

-General structure

A

-Bundle of alpha-helical transmembrane segment

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31
Q

Bonds associating peripheral proteins to membrane

A

Electrostatic interxn and H bonding with hydrophilic domains of IPs & polar head groups

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32
Q

Major determinant of transition temperature (solid -> semi solid)

A

Lipid composition

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33
Q

Membrane fluidity is dependent on

A

Lipid composition
-more saturated & longer = higher transition temp

Temp
-higher temp = ordered to disordered

34
Q

At low temperature, lipids in a bilayer are in what form? At high temp? Intermediate?

A

Semisolid gel phase = PARACRYSTALLINE STATE; uniformly arrayed at surface and acyl chains are nearly motionless and packed with regular geometry

At high temp, liquid-disordered or fluid state

At intermediate temp, liquid-ordered state

35
Q

Equalization of the concentration across the membrane can be circumvented by:

A
  1. Binding of substance to macromolecules
  2. Maintaining a membrane potential
  3. Coupling transport to an exergonic process
36
Q

3 types of lipid aggregates

A
  1. Micelles
  2. Bilayer
  3. Liposome
37
Q

Micelles

  • Characteristics
  • Function
  • Formation depends on?
A

Micelles

  • Amphipathic lipids that aggregate into spheres
  • Important in intestinal digestion and absorption of lipids
  • Formation depends on temperature and mixture & ratio of lipids
38
Q

Bilayer
-Characteristics

  • Formation
  • Stability
A
  • Two lipid monolayers forming a 2D sheet
  • When xs areas of head group and acyl chain are similar
  • Relatively unstable and spontaneously form liposomes
39
Q

Liposomes

  • Formation
  • Function
A

Liposomes form when bilayer folds back on itself forming a hollow sphere -> vesicle -> liposome

Lose the hydrophobic edge achieving max stability

Function:
-Can entrap thus can be used as drug carriers and vectors of gene therapy

40
Q

T or f. Some biological cells have no receptors.

A

f!!!!!

41
Q

3 common types of membrane receptor proteins?

A
  1. GPCR
  2. RTK
  3. Ion channel receptors
42
Q

What type of receptor?

  1. Glucagon
  2. Glutamate
  3. EPO
  4. Aminobutyric acid
  5. Acetylcholine
  6. Insulin
A
  1. GPCR
  2. Ion channel receptor
  3. RTK
  4. Ion channel receptor
  5. GPCR
  6. RTK
43
Q

Limitations of passive transport? Why does this occur?

A

(1) Thermal agitation
(2) concentration gradient
(3) Solubility of solute

Occurs due to random thermal movement; with the concentration gradient

44
Q

What is Vmax? Km? Which type of transport are they applicable?

A

Vmax = maximum rate of transport

Km = binding constant

Applicable for facilitated diffusion and active transport

45
Q

Facilitated diffusion rate is dependent on which factors?

A

1 conc gradient

2 amount of carrier available

3 rapidity of solute carrier interaction

4 rapidity of conformational change for both loaded and unloaded carrier

46
Q

How do hormones regulate facilitated diffusion?

A

By changing number of transporters available

47
Q

Facilitated Diffusion vs. Active Transport vs. Simple Diffusion?

A

Simple Diffusion
-Happens to small or nonpolar particles

Faci Diff

  • happens to large or polar particles
  • can occur bidirectionally

Active
-unidirectional; against conc gradient

48
Q

Uniport vs CoTransport?

A

Uniport
-moves 1 type of molecule bidirectionally

Co-Transport
-Transfer of system of one solute depends upon stoichiometric simultaneous or sequential transfer of another solute

49
Q

Symport vs. Antiport

A

Symport
-moves 2 solutes in the same direction

Antiport
-moves 2 solutes in different direction

50
Q

The specificity of channels and pores depend on?

A

Size and charge of the substance

51
Q

Pore vs. Channel vs. Carrier

a. Conduit through membrane
b. Unitary event

A

a. Always Open - Intermittently open - never open

B. None (continuously open) - open/close - cycle of conformational changes

52
Q

T or F. Ion channels are opened transiently and thus called gated.

A

T!!!

53
Q

Water channels?

a. Name
b. Characteristic/structure
c. How does it exclude H3O+

A

A. Aquaporins <3

B. Functions as tetramers of identical monomers; Each monomer had 6 spanning helices that contain a conserved N terminal Asn-Pro-Ala (NPA)

C. By electrostatic repulsion due to presence of Arg at the constriction

54
Q

Membrane-microdomains of lipid protein complexes?

A
  1. Lipid Rafts
  2. Caveolae
  3. Tight Junctions
55
Q

What are lipid rafts? Function

A

Dynamic areas of exosplasmic leaflet of lipid bilayer enriched in cholesterol, sphingolipids, and certain proteins

Segregate and cluster increasing efficacy of signal transduction and other processes

56
Q

Caveolae

A
  • Derived from lipid rafts
  • contains caveolin 1
  • Flask shaped indentations of cell membranes
57
Q

A special class of membrane rafts which consists of an integral membrane protein with 2 globular domains connected by a hairpin shaped hydrophobic domain which binds the protein to the cytoplasmic leaflet of the PM

A

Caveolin

58
Q

Aka little caves which is responsible for signal transduction of insulin; membrane trafficking within cells and transduction of external signals into cellular responses

A

Caveolae

59
Q

What are integrins

A

Heterodimeric proteins anchored to PM by a single hydrophobic transmembrane helix in each subunit

-Regulator of many processes e.g. platelet aggregation

60
Q

Cross membrane movement of small molecules?

A

> Diffusion

> Active transport

61
Q

Cross membrane movement of large molecules?

A

> Endocytosis

> Exocytosis

62
Q

Signal transmission across membranes

A

> CSR (Signal transduction and signal internalization)

> Movement to intracellular receptors

63
Q

Cell Transport of Macromolecules?

A

Endocytosis, Exocytosis, Phagocytosis, Pinocytosis

64
Q

What is absorptive pinocytosis

A

Receptor mediated selective process primarily responsible with finite binding sites on PM

65
Q

3 fates of molecules released by exocytosis

A
  1. Attach to the cell surface and become a peripheral protein
  2. Become part of ECM
  3. Can enter ECF and signal other cells
66
Q

Classifications of Transporters

A
  1. ATPase
  2. ABC
  3. Solute Carrier Transport
67
Q

ATPase

-Types

A
  1. E-type (involved in extracellular transport)
  2. F-type (for translocation of H in mitochondria)
  3. P-type (at PM)
  4. V-type (vacuoles and lysosomes)
68
Q

4 steps in transport of solute molecules

A
  1. Recognition
  2. Translocation
  3. Release of substrate
  4. Recovery
69
Q

Glut

Glut5

A

Glut - uniport from out to in; except erythrocyte glut (bidirectional)

Glut 5: prefers fructose

70
Q

Where is this molecule more abundant?

Na, K, Ca, Mg, Cl, HCO3, PO4, Glucose, Protein

A

ECF - Na, Ca, Cl, HCO3, Glucose

ICF - K, Mg, PO4, Protein

71
Q

Which compartment contains more water?

A

Intracellular contains 2/3 of TBW

72
Q

Mutations of gene encoding AP-2

A

Nephrogenic Diabetes Insipidus

73
Q

In Diptheria toxin, what is affected?

A

Ionophores

74
Q

Mutation in gene encoding FGF3 receptor

A

Achondroplasia

75
Q

Mutation in gene encoding LDL receptor

A

Familiar hypercholesterolemia

76
Q

Abnormalities in CFTR protein and CI transport

A

Cystic fibrosis

77
Q

Abnormalities in the ion channels of the heart

A

Congenital long QT syndrome

78
Q

Copper dependent ATPase

A

Wilson’s Disease

79
Q

Abnormalities in GlcNac phosphotransferase resulting in absence of Man-6-P signal for lysosomal localization of certain hydrolases

A

I cell disease

80
Q

Abnormalities in spectrin and other structural proteins in RBC

A

Hereditary spherocytosis

81
Q

Abnormalities in oligosaccharide chains of membrane glycoproteins and glycolipids

A

Metastasis

82
Q

Deficiency in the attachment of GPI anchor to certain proteins of the RBC

A

Paroxysmal Nocturnal hemoglobinuria

Biochemistry (11 decks)

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