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Biochemistry I > Chapter 11 Membranes > Flashcards

Chapter 11 Membranes Flashcards

1
Q

What kind of structure is the biological membrane?

A

sheet like, few molecules thick, and self sealing

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2
Q

What does the biological membrane contain?

A

Contain amphipathic lipids, proteins and carbohydrates. Non-covalent Interactions (van deer walls which attract the nonpolar tails together)

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3
Q

_______ carry out most of the specific functions on the biological membrane.

A

Proteins

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4
Q

What are the membrane proteins functions contain?

A

receptors, enzymes, ion channels, calcium pumps

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5
Q

What are the carbohydrates on the membrane important for?

A

(attached to lipids = glycolipids, or to
proteins = glycoproteins) - important in communication/recognition
This is also the function of the post-translational modification (review assignment sheet)

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6
Q

What is the hydrophobic effect?

A

major driving force of the lipid bilayer

for example: mixing lipids and oils into water

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7
Q

______ and _______ form a lipid bilayer.

A

phospholipids and glycolipids

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8
Q

Membranes are _______ in that the outer surface is always different from the inner surface.

A

asymmetric (asymmetric arrangement)

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9
Q

Is the biological membrane polarized or unpolarized?

A

polarized: inside is negative (-60mV). Plays a role in transport, energy conversion and excitability.
- -Inside of axon is (-) and the ECF is (+)

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10
Q

What are the two types of diffusion in lipids?

A

Lateral and Transverse diffusion

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11
Q

Define lateral diffusion

A

rapid change of solid to liquid state

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12
Q

Define transverse (flip-flopping) diffusion

A

very slow (rare) change of solid to liquid state

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13
Q

How did they proof lateral diffusion existed?

A

They let bleach sit on a sample with lots of lipids and did a fluorescent recovery (FRAP) and found there was movement b/w lipids

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14
Q

What is the The Fluid Mosaic Model?

A

it describes the lipid bilayer of vesicles as a dynamic, liquid-like environment that allows the free motion of non-polar molecules throughout its structure.
(Proposed by Singer and Nicolson in 1972)

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15
Q

What are liposomes?

A

they are aqueous compartments enclosed by a lipid bilayer

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16
Q

What are the function of liposomes (lipid vesicles)?

A

they deliver chemicals/drugs/DNA to specific tissues

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17
Q

What is so special about liposomes?

A

They have an inner and outer aqueous compartment which helps in delivering chemicals to tissues. The aqueous compartments are enclosed by a lipid membrane

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18
Q

What is the function of the homing peptides on the outside of liposomes?

A

they help target what organ to go to

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19
Q

_____ have a harder time getting through the membrane when attached to H2O. They have to release the H2O as they go through the ______ to get through the membranes.

A 
Charged ions (Na, K, Cl) 
channels
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20
Q

H2O is special when going through membranes because it goes through by ________.

A

simple diffusion

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21
Q

When you have saturated fatty acids, more viscous (tightly packed), does the fluidity increase or decrease?

A

Decrease

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22
Q

When you have unsaturated (kinked) fatty acids, does the fluidity increase or decrease?

A

Increase

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23
Q

In saturated fatty acids (no double bonds), what does the melting temp and fluidity do? Increase or decrease?

A

Melting temp INC

Fluidity DEC

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24
Q

In unsaturated fatty acids (double bonds present), what does the melting temp and fluidity do? Increase or decrease?

A

Melting temp DEC

Fluidity INC

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25
Q

Solid like means long chain fatty acids OR short chain fatty acids and saturated OR unsaturated fatty acids?

A

long chains of fatty acids

saturated (more compact)

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26
Q

Fluid like means long chain fatty acids OR short chain fatty acids and saturated OR unsaturated fatty acids?

A

short chains of fatty acids

unsaturated (less compact)

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27
Q

What are the 4 factors that determine solid like and fluid like?

A

Temperature, chain length, saturation vs. unsaturated, cholestrol

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28
Q

As the temperature increases, is that solid like or fluid like?

A

fluid like

29
Q

As the temperature decreases, is that solid like or fluid like?

A

solid like

30
Q

Longer chain of carbons, then its more compact, which means more ______ like.

A

solid

31
Q

Unsaturated fatty acid means more kinks, which ______ fluidity

A

increase

32
Q

__________ disrupts the tight packing of the fatty acid chains, therefore it is more ______ like.

A

Cholesterol, fluid

33
Q

While membrane _______ establish a permeability barrier, membrane ______ allow transport of molecules and information across the membrane.

A

lipids

proteins

34
Q

the more proteins, the MORE ______ are being transferred

A

molecules and ions

35
Q

Integral Membrane Protein is embedded where?

A

in the membrane

36
Q

Peripheral Membrane Protein is located where?

A

NOT embedded in the membrane, attached to extracellular surface

37
Q

How are peripheral proteins attached to the surfaces of membranes (EC surfaces)?

A

Through being bound to head groups of lipids by electrostatic and hydrogen-bond, bound to integral membrane protein, or post-translationally modified to contain a fatty acid chain.

38
Q

For one example of a peripheral membrane protein, the polimitate attaches to the ______ in the membrane.

A

cytseine

39
Q

In an integral membrane protein, what would be the properties of the amino acids in the protein?

A

most of them are hydrophobic amino acids because they are embedded in the membranes away from the ECF

40
Q

in porin, there is a barrel that allows the entry of charged ions and it has _______ amino acids on the inside

A

hydrophilic

41
Q

Any protein that gets halfway or a quarter of the way through a membrane is classified as a _________

A

Intergral membrane protein

42
Q

In the formation of prostaglandin H2 from arachidonate by prostaglandin H2 synthase, how many steps are needed for the final product?

A

2

43
Q

____________ +___________ =

Prostaglandin H2 synthase

A

Cyclooxygenase + Peroxidase

44
Q

What does the formation of prostaglandin H2 do?

A

Promotes inflammation & modulates gastric acid secretion. It produces fever.

45
Q

How does ASA work?

A

-Aspirin inhibits cyclooxygenase activity by obstructing the channel which causes a conformational change with the protein and the arachidonic cant bind

46
Q

What is the criteria for a molecule being able to pass through a membrane through simple diffusion?

A
  1. The concentration of the molecule is higher on one side of the membrane than the other.
  2. The molecule is lipophilic or soluble in nonpolar solutions.
47
Q

Polar molecules can diffuse across a membrane down their concentration gradient only with the assistance of a particular protein called a channel. Such movement is called ______ or _______.

A

facilitated diffusion or passive transport

48
Q

Movement of molecules against a concentration gradient requires a source of energy and is called________.

A

Active tranport

49
Q

What are the factors that determine simple diffusion across a membrane?

A

no assistance needed and molecules that dissolve in lipid.

Ex: Lipophilic molecule such as steroid

50
Q

What are the factors that determine Passive Transport/Facilitated Diffusion across a membrane?

A

-Rate of diffusion enhanced by carrier or channel (integral
membrane protein) and Rapid diffusion “down a concentration gradient
-Energy comes from the molecule itself
EX: sodium ions

51
Q

What are the two types of active transport?

A

Primary and secondary

52
Q

What is primary active transport?

A

transport of solute against its concentration gradient, where ATP required

53
Q

What is secondary active transport?

A

ATP required; flow of one molecule promotes flow of another molecule (Antiporters vs symporters)

54
Q

As the solute increases, the rate of transport ______

A

Increases

55
Q

Functions of the Na+-K+ Pump (Na+-K+ ATPase)

A
  • Controls cell volume
  • Promotes electrical excitability
  • Drives transport of sugars and Amino acids
56
Q

What does Na+-K+ Pump pump? and where is the ATP located to drive the pump?

A

Pumps 3 Na+ out & 2 K+ into cell. ATP inside to drive the pump

57
Q

Why are channels called P-type ATPases?

A

because the channel is phosphorylated and changes conformation

58
Q

Examples of primary active transport

A

Na+-K+ ATPase
Ca2+ ATPase
H+-K+ pump

59
Q

Examples of secondary active transport

A

Na+ -glucose symporter

Na+- Ca2+ Exchanger

60
Q

In order for secondary active transport to work, it has to be what?

A

Coupled with a primary active transport

61
Q

What is an antiporter secondary transport system?

A

the two substrates flow in opposite directions (ex: Na+ Ca+ channel)

62
Q

What is a symporter secondary transport system?

A

the two substrates flow in the same direction (ex: Na+ glucose channel)

63
Q

What are the 3 voltage gated cahnnels?

A

Na, K, and Ca

64
Q

How does the selectivity filter work?

A

-Ion path begins (on inner surface) as wide, water-filled channel, so cations can enter with hydration sphere intact.
Partway through membrane, channel narrows, so waters of hydration have to come off.
-Carbonyl O atoms from protein backbone in selectivity filter region replace water molecules, binding to K+, with a series of perfect coordination shells through which K+ can move.
-Na+ ions can’t interact favorably with the filter (they’re too small) and they don’t release the water as easily as K+.

65
Q

What is Digitalis’s function?

A

inhibits the Na+-K+ pump

  • increases Na+ inside of the heart and decreases K+ in the heart.
  • increase in intracellular Na+ slows down the expulsion of Ca2+.
  • increase in Ca2+ enhances contraction of the heart
66
Q

Digitalis information

A

in heart disease the patients need the Ca+ in the cells so the digitalis is a drug that blocks the Na+ K+ pathway so more na+ is on the inside which then blocks the secondary AT and more Ca+ is stored on the inside
—The INC of Ca+ enhances the contraction of the heart

67
Q

MultiDrug-Resistance (MDR) Proteins or

P-glycoprotein are over expressed in what?

A

tumors, drugs like chemo cant enter the cell because the cell uses the ATP to spit the drug out

  • This is because the tumors build a resistance to the drugs
  • 4 domains: 2 membrane spanning domain and 2 ATP-binding domain (ATP-binding cassettes-ABC).
  • ABC transporters
68
Q

Where is the defect in this disease Harlequin Ichthyosis?

A

defect in ABC transporter for lipids in keratinocytes

Biochemistry I (7 decks)

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