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my packs: (wizeprep) (biochem 2280) > Chapter 6: 6.2 Membranes > Flashcards

Chapter 6: 6.2 Membranes Flashcards

1
Q

Different membranes have different —– ——–

A

Lipid profiles

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2
Q

What are membranes made up of?

A

A variety of lipids and proteins

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3
Q

What do the membrane compositions represent?

A

Represents a fluid mosaic model

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4
Q

What diffuses rapidly throughout the plane of the membrane?

A

Lipids

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5
Q

True or False:

In membranes, protein composition is always the same

A

False, protein composition is random

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6
Q

Protein are able to travel ——— throughout the membrane

A

Laterally

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7
Q

What forces are involved in membrane lipid assembly?

A
  1. Hydrophobic effect
  2. Van der Waals forces
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8
Q

Different lipids yield different membranes, what lipid shapes are there?

A
  1. Cone
  2. Cylinder
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9
Q

Why do polar lipids aggregate?

A

To minimize contact between water and their hydrocarbon chains

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10
Q

What do cone shaped lipids form?

A

Micelles

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11
Q

What do cylinder shaped lipids form?

A

Bilayers

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12
Q

What does membrane fluidity depend on in the membrane?

A

Lipids within the membrane

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13
Q

List:

Properties of lipids that affect membrane fluidity

A
  1. Saturation
  2. Hydrocarbon length
  3. Cholesterol
  4. Headgroup
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14
Q

Define:

Tm

A

Phase Transition Temperature
* Midway point between gel-like and fluid membranes

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15
Q

Describe:

Structure of membrane hydrocarbons as it moves from solid to fluid

A

Hydrocarbons chang from anti-conformation to gauche conformation resulting in more “kinks”

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16
Q

What R Groups affect Tm?

A
  • Choline
  • Ethanolamine
  • Glycerol
17
Q

True or False:

The longer the chain length, the higher the Tm

A

True

18
Q

The tighter the packing of the kipids…

A

The more solid the membrane

19
Q

At lower temperatures, membranes have more…

A

Unsaturated hydrocarbon chains

20
Q

At higher temperatures, membranes have more…

A

Saturated hydrocarbon chains

21
Q

What does cholesterol act as in membrane fluidity?

A

Cholesterol acts as a “buffer”

22
Q

What does it mean that cholesterol acts as a “buffer”?

A

It disrupts lipid packing as well as provides rigidity

23
Q

Describe:

High Temperature Adaptations of Hypothermophilic Archaea

A

Have a lipid called caldarchaeol
* Stabilizes the membrane even more at high temperatures

24
Q

What high temperature adaptations are present on hydrocarbons chains?

A

Hydrocarbon chains are linked with glycerol at both ends

25
Q

Describe:

Membrane Lipid Dynamics

A

Lipids move laterally in the membrane very rapidly (1 μm/s)
* Transverse diffusion is much slower

26
Q

Why is transverse diffusion so much slower?

A

The polar head group does not easily pass through the hydrophobic interior

27
Q

In transverse diffusion:

What move lipids from the outer membrane to the inner membrane?

A

Flippases

28
Q

In transverse diffusion:

What moves lipids from the inner membrane to outer membrane?

A

Floppases

29
Q

In transverse diffusion:

What transports lipids from either side of the membrane to the other?

A

Scramblases

30
Q

Define:

FRAP

A

Fluorescence Recovery After Photobleaching

31
Q

State:

Steps of FRAP

A
  1. Fluorescently label lipids
  2. Bleach membrane
  3. Monitor how quickly fluorescence returns
32
Q

What does FRAP show?

A

Show that lipids rapidly diffuse laterally

33
Q

Describe the process of:

Freeze Fracture EM of the Membrane

A
  1. Freeze cells to -196°C in liquid nitrogen
  2. Fracture membrane )opens along interface of lipids)
  3. Separate the two halves
  4. Make a carbon-metal replica of each half
  5. Observe via electron microscopy (EM)
34
Q

What can freeze fracture EM of the membrane show?

A

Shows that membrane protein distribution is random

35
Q

Describe the process of:

Single Molecule tracking of Phospholipids/proteins

A
  1. Label phospholipid/protein
  2. Place in a live kidney (contains compartments)
  3. Track with microscope
36
Q

What can single molecule tracking of phospholipids/proteins?

A

Shows that lipids diffuse quickly and freely between compartments, but protein remained contained within compartments longer

37
Q

What can diffusion be impeded by? (4)

A
  1. Actin cytoskeleton barriers on the underside of membrane
  2. Organelle membranes contacting the plasma membrane
  3. Extracellular matrix linked to the membrane proteins
  4. Immobile membrane protein and lipid clusters

my packs: (wizeprep) (biochem 2280) (19 decks)

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