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Biochem > Lecture 10 Information > Flashcards

Lecture 10 Information Flashcards

1
Q

Fluid mosaic model

A

the proteins and the phsopholipids themsleves are moving within the plane of the membrane

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2
Q

How do constituents of the cell membrane move?

A

through non-covalent weak interactions, allows for lots of curvature and flow

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3
Q

Micelle

A

individual units are wedged shape

lipid tails funnel inwards and heads are water

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4
Q

Vesicles

A

lipid bilayer with aqueous cavity

beginning of life on earth

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5
Q

What is bilayer formation driven by?

A

hydrophobic interactions and increasing entropy in the aqueous outside environment

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6
Q

Are the two layers of the bilayer membrane symmetric?

A

No

The two layers are asymmetric and the inner/outer leaflets can have different lipid constituents

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7
Q

Integral membrane proteins

A

imbedded in the protein

have membrane spanning sections

amino acids are hydrophobic

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8
Q

How can integral membrane proteins be removed?

A

detergents interact with the hydrophobic regions and remove integral membranes

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9
Q

Peripheral membrane proteins

A

associated with other proteins/components of the membrane

Not imbedded in the membrane or held covalently to the membrane

Associated to membrane through weak interactions

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10
Q

Amphitropic membrane proteins

A

association with membrane is biologically regulated

can have covalent interactions with the membrane

dynamic association

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11
Q

Transmembrane alpha-helicies

A

strongly anchor proteins in the membrane

can have one or multiple helicies

regions with high hydropathy on a plot can indicate where transmembrane alpha-helicies lie

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12
Q

Example of a transmembrane alpha-helix

A

bacteriorhodopsin-7

membrane spanning protein

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13
Q

Trp and Tyr residues in membranes

A

located at the interface (intersection of hydrophillic and hydrophobic regions) of the membranes

amphipathic quality of their R-groups allows for them to mediate between hydrophillic outer surface and hydrophobic intersurface

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14
Q

Where do positively charged amino acids tend to be located in the membrane?

A

on the inner leaflet of the cell

the cell tends to be negatively charged, so the positive amino acids interact with the negatively charged cell interior

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15
Q

The beta barrels

A

not as predictable or long as membrane spanning alpha helicies

beta sheet R groups are pointing out of the plane and into the plan in an alternating manner

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16
Q

Lipid linked membrane proteins

A

proteins are covalently attached to some membrane anchoring lipid

only found on the inner leaflet

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17
Q

Examples of lipid linked membrane proteins

A

Phosphatidylserine and PIP2

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18
Q

GPI proteins

A

found only on extracellular surface of the cell

in general, carbohydrate groups are found on the outside of the cell membrane in order to serve as cellular identification

ex: blood type sphingolipids

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19
Q

What happens to membrane fluidity if temp is under the physiological temp?

A

enter the gel phase with restricted motion and paracystalline structures

too rigid

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20
Q

What happens to membrane fluidity if temp is above the physiological temp?

A

liquid disordered state, too much fluidity and the cell might start letting in molecules that it shouldn’t

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21
Q

What happens to membrane fluidity when temp is at the physiological temp?

A

At the physiological temp, liquid ordered state, less thermal motion, but still allows for lateral movement in the plane of the bilayer

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22
Q

What type of lipids does the membrane use at higher temperatures?

A

lipids that are more saturated, making the membrane less fluid

*reverse is true at lower temps

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23
Q

How to visualize cholesterol?

A

acts like a barrel floating on top of the cell membrane

24
Q

Cholesterol at high temperatures

A

the barrels will impede the movement of water

water bumps into the barrel and stops

25
Q

Cholesterol at low temperatures

A

cholesterol stops the water molecules from associating with each other (barrels are physically in the way)

increases fluidity

26
Q

hop diffusion

A

moves lipids to different regions of the membrane very quickly

then, fast local movement occurs within a region

27
Q

Why is moving of phospholipids from one leaflet to the other unfavored?

A

Inside of membrane is hydrophobic, so it is hard to get hydrophilic head to move through the hydrophobic region to the other side

28
Q

Why do we need to regulate lipid movement from one leaflet to the other?

A

over time, an equillibrium would be reached and the membrane would become symmetric

29
Q

Flipases

A

take aminophospholipids (PE and PS) on the extracellular leaflet and move to cytosolic leaflet

requires ATP

Flip extracellular leaflets that might signal apoptosis to the inside, so apoptosis is not triggered

30
Q

Floppase

A

take phospholipids on the intracellular leaflet and flip them to the extracellular leaflet

Require ATP

31
Q

Scramblase

A

scrambles the concentrations of phospholipids in the membrane and opens the door for the phospholipids to move down their natural concentration gradients

Phospholipids will approach equilibrium/symmetric gradient faster

Scramblases have a role in apoptosis

ATP not needed since moving phospholipids down their concentration gradient

32
Q

Lipid rafts

A

areas of the bilayer are thicker because they are composed of phospholipids that have longer chains of fatty acids

made of glycosphingolipids (gangliosides/cerebrosides)

saturated fatty acids

33
Q

What do lipid rafts create?

A

regions with specific proteins associated that controls the chemistry in these regions

specific environment within the membrane

34
Q

Simple diffusion

A

small hydrophobic molecules can get through the membrane

35
Q

Facilitated diffusion

A

going down a concentration gradient

No ATP required

using a protein to allow molecule to travel down the gradient

36
Q

Ion channels

A

free flow of materials through the membrane, mostly using the concentration gradient

generally don’t use ATP

37
Q

Uniport

A

moves one molecule down gradient

38
Q

Synport

A

moves two molecules in the same direction

39
Q

Antiport

A

moves two molecules in different directions

40
Q

Differences between transporters and channels

A

Transporters bind the molecule with high selectively and can be saturated

Transporters do not increase rate that much compared to channels

Channels carry molecules with low selectively

41
Q

Aquaporins

A

a type of channel

move water through membrane at high rate

42
Q

Aquaporins and hydronium

A

prevent hydronium from passing through by placing positively charged histidine and asparagine within the interior of the porin

43
Q

NPA sequence

A

aparaginine proline and aspartate

Asparagine is able to hydrogen bond to water

By replacing hydrogen bonds between water and water, with water and asparagine we keep the movement of water energetically favorable

44
Q

How do you regulate and turn off the flow of water?

A

phosphylate at serine

Changes the structure and removes NPA regions from central region and water cannot go through the aquaporin

45
Q

GLUT1

A

a type of passive transporter for glucose

made up of alpha helicies with hydrophobic outside and hydrophillic inside

46
Q

Chloride-bicarbonate exchanger

A

another type of passive transporter

exchanges chloride for bicarbonate as bicarbonate is pushed out of the cell

negative for negative charge maintains electrical balance

antiport: two molecules move in different directions

no ATP since moving with the gradient

47
Q

Pumps

A

move solutes up concentration gradient and require ATP

48
Q

Primary active

A

solute accumulation coupled directly to an exergonic reaction (like ATP hydrolysis)

49
Q

Secondary active

A

endergonic transport of one solute couples to the exergonic flow of another solute that was originally pumped uphill by a primary active pump

50
Q

Sodium-Potassium pump

A

primary active transporter

antiport: 2 K+ comes in and 3 Na+ goes out

Cotransporter: phosphorylation of a critical Asp causes conformational changes

51
Q

Lactose transporter

A

secondary active transporter

Initial endergonic pumping of H+ out / the exergonic flow of H+ in is coupled to allow lactose to flow against its gradient

After H+s are pumped against their gradient, they fall back down their natural gradient and take lactose with them

52
Q

Hydrogen cyanide

A

blocks the proton gradient and therefore blocks lactose from flowing into cell

does the same thing with ATP synthesis

53
Q

What prevents phospholipids from moving from leaflet to leaflet?

A

high energetic cost of moving the hydrophilic heads across the hydrophobic interior

54
Q

Where are phosphatidylethanoalmine and phosphatidylserine found?

A

on the inner membrane leaflet

55
Q

Where are phosphatidylcholin and sphingomyelin found?

A

on the outer membrane leaflet

Biochem (20 decks)

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