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BIOCH 200 > Membranes > Flashcards

Membranes Flashcards

1
Q

Lipids

A

Nonpolar
Hydrophobic
Insoluble in water

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2
Q

Types of Lipids

A

Fatty acids
Triacylglycerides
Membrane lipids
Cholesterol

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3
Q

Fatty Acids

A

Long-chain hydrocarbon carboxylic acids
-general formula=CH3(CH2)nCOO-
Amphipathic (COO- is polar)

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4
Q

Saturated Fatty Acids

A

No double bonds

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5
Q

Unsaturated Fatty Acids

A

Has double bonds

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6
Q

Monounsaturated Fatty Acids

A

1 double bond

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7
Q

Polyunsaturated Fatty Acids

A

More than 1 double bond

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8
Q

Where are double bonds most common?

A

In cis conformation

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9
Q

How do double bonds affect the melting point?

A

Decreasing the melting point by introducing kinks

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10
Q

Shorthand Notation for Fatty Acids

A

(number of carbons):(number of double bonds)(delta)^where the bonds are

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11
Q

How does length affect the melting point

A

Longer=higher melting point

Shorter=lower melting point

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12
Q

How does saturation affect the melting point

A

Saturated=higher melting point
Unsaturated=lower melting point
Greater effect on melting point than length

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13
Q

Triacylglycerol

A

Way of storing fatty acids

Very hydrophobic

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14
Q

Triacylglycerol Structure

A

3 acyl chains attached to glycerol

Acyl chains from fatty acids (ester-linked)

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15
Q

What type of triacylglycerols is most common?

A

Mixed TAGs

the melting point will be lower for those containing unsaturated fatty acids or shorter chains

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16
Q

Glycerophospholipids

A

2 acyl groups and a large polar group attached to glycerol

amphipathic

17
Q

Cholesterol

A

Rigid, nonpolar structure
Weakly amphipathic
Found in membrane lipids
Does not form membranes alone
-associates with polar headgroups of other lipids
-nonpolar portion is found in the membrane

18
Q

Lipid Interactions in water

A

Fatty acids from micelles when mixed in water

Membrane lipids form a bilayer when mixed in water

19
Q

Dimensions of a lipid bilayer

A

Variable
Lipid head groups have significantly different dimensions
Acyl chains vary in length
Cholesterol is almost entirely buried in the bilayer

20
Q

The fluidity of membrane lipids

A

The melting temperature is the temperature of its transition from an ordered crystalline to a more fluid state
Depending on the acyl chain length and unsaturation

21
Q

Why is the transition temperature not sharp?

A

Mixture of compounds
Membranes must operate above melting point but not be completely disordered
Lipids must adjust to maintain fluidity

22
Q

How do membranes maintain fluidity?

A

Lower temperature = more unsaturated and shorter fatty acids are incorporated
Higher temperature = more saturated and longer fatty acids are incorporated

23
Q

How does cholesterol help maintain membrane fluidity?

A

Lower temperature = prevents packing between acyl chains

Higher temperature = decreases motion/disorder of acyl chains and increases rigidity

24
Q

Why do lipids only move laterally in the bilayer?

A

Provides membrane fluidity

-weakly hydrophobic interactions

25
Q

Why don’t lipids undergo transverse diffusion?

A

The significant energy barrier for desolvating a polar head to move through the nonpolar bilayer
-flipases would be needed

26
Q

Types of Membrane Proteins

A 
Integral membrane protein
-hydrophobic interactions
Peripheral membrane protein 
-electrostatic/polar
-easy to separate from lipid
Lipid-linked protein
-lipid prosthetic group
-hydrophobic anchor
27
Q

Integral Membrane Proteins and Hydrophobic Amino Acids

A

The portion of protein connected to acyl tails must have hydrophobic amino acids side chains

28
Q

What can cross bilayer by diffusion

A

Small, nonpolar molecules

29
Q

What does the rate of diffusion depend on?

A 
Size of molecule
-smaller moves faster
Concentration gradient
-larger gradient increases the rate
Lipid solubility 
-increases the diffusion rate
30
Q

Passive Transport

A

No ATP required

If G=negative, motion is spontaneous which is passive

31
Q

Active Transport

A

ATP required

If G=positive, energy is required which is active

32
Q

What does G need to be for transport to occur?

A

Negative

33
Q

Porins

A

Relatively non-specific
Water-filled pore in the center of the barrel
Most are trimers (3 pores)
Passive

34
Q

Ion Channels

A

Highly selective
Channel formed between subunits
Selectivity depends on the size of the pore and the properties of the side chains/functional groups found there
Can be passive or active

35
Q

Transporter Proteins

A 
Carrier proteins
No membrane-spanning pores
Conformational change alternates openings
Selective
Passive or active
36
Q

Uniport

A

Transports one type of substrate

37
Q

Symport

A

Trasport of two molecules in the same direction

38
Q

Antiport

A

Transports two molecules in opposite directions

Secondary Active Transport

39
Q

Primary vs Secondary Active Transport

A 
Primary = uses ATP as a source of free energy
Secondary = uses ion gradient as a source of free energy

BIOCH 200 (9 decks)

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