Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

BIO353 > Chapter 11 - Membrane Structure > Flashcards

Chapter 11 - Membrane Structure Flashcards

1
Q

How do cells perform their functions?

A

A series of specific chemical reactions (in aqueous solutions).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Cells must have a physical barrier to ____ their ___ ___ from the ___ ___

A

separate, internal contents, outside environment.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

A membrane cannot be…?

A

Randomly permeable to most of the hydrophilic molecules, or water soluble.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What does a membrane need to provide?

A

Selective permeability to specific molecules under specific conditions.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What do membranes do?

A

1) Partition (divides) water and molecules soluble in water

2) Compartmentalize enzymes to increase chemical reaction efficiency.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are selectively permeable membranes?

A

A hydrophobic permeability barrier comprised of amphipathic (having both hydrophilic and phobic parts) molecules.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

The lipid bilayer sequesters what?

A

Hydrophobic phospholipid tails with hydrophilic head groups.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Are transport proteins present on the membranes?

A

Yes, and they enable selective permeability.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What are the major classes of lipids on the membrane?

A

Phospholipids, glycolipids, sterols, cholesterols, phytosterols, hopanoids (sterol-like molecules in prokaryotes).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What are the main components of fatty acids?

A

Carboxyl group (-COOH, favors water), and hydrocarbon chains (unfavors water).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What acts as a source of energy and a precursor of membrane phospholipids?

A

Fatty acids.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Fatty acids are used to form what?

A

Triglycerides.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

When a cell needs energy, the fatty acid chains can be released from the _____ and broken down.

A

Triacylglycerols.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What are the most abundant types of lipid in membranes?

A

Phospholipids.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What are the major lipid component of cell membranes?

A

Phospholipids.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Phospholipids are composed of two ____ fatty acid tails joined to a ____ head.

A

hydrophobic, hydrophilic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Can phospholipids differ in their head group?

A

Yes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

(T/F) Cholesterol is present in all animal membranes?

A

True

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What fits between phospholipids, especially those with unsaturated fatty acid tails?

A

Cholesterol

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What resolves the conflicting forces that amphipathic molecules are subjected to in an aqueous environment?

A

The formation of the lipid bilayer.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

(T/F) The membrane bilayer are in constant motion.

A

True.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

(T/F) The higher the temperature for a lipid bilayer the slower they move.

A

False.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What are the three movements phospholipids can undergo?

A

1) Rotation and flexion (being bent)
2) Lateral diffusion
3) Transverse diffusion/ flip-flop.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What are used for phospholipid translocators?

A

Flippases and scramblases

25
Q

A fluid bilayer permits ___ ___ of membranes as well as ___.

A

lateral diffusion, proteins.

26
Q

Where does membrane phospholipid synthesis occur?

A

In the ER on the cytosolic side of the membrane.

27
Q

What does scramblases do?

A

It moves newly synthesized phospholipids to the opposite monolayer.

28
Q

(T/F) Most lipids (and proteins) are distributed unequally between the two monolayers.

A

True

29
Q

What organelle causes membrane asymmetry?

A

The Golgi apparatus.

30
Q

What initiates and maintains membrane phospholipid asymmetry?

A

Flippases.

31
Q

What is transition temperature (Tm)?

A

the membrane gels (“freezes”) when cooled and becomes fluid again (“melts”) when warmed.

32
Q

What is phase transition?

A

The change in the state of the membrane?

33
Q

The ___ can function properly - only when ____.

A

membrane, the temperature is above its Tm.

34
Q

Homeoviscous adaptation

A

Oranisms can compensate for temperature changes by altering the lipid composition of their membranes, thereby regulating membrane fluidity.

35
Q

What do forces between phospholipids influence?

A

Membrane fluidity.

36
Q

What forces make a membrane more gel-like?

A

Attractive forces (long fatty acid tails mean more van der Waal attractions, and H-bonds between head groups).

37
Q

What forces make a membrane more fluid?

A

Repulsive forces (charged head groups, double bonds in unsaturated fatty acid tails).

38
Q

What causes steric hindrance?

A

Double bonds in unsaturated fatty acid tails. Double bonds cause kinks in tails which keep phospholipids apart.

39
Q

What is steric hindrance?

A

The slowing of chemical reactions due to their bulky size.

40
Q

What leads to less fluidity in the membrane?

A

Increasing length of fatty acid side chains.

41
Q

What leads to more fluidity in the membrane?

A

Increasing percentage of unsaturated fatty acids.

42
Q

What causes the membrane to be less fluid at higher temperatures?

A

Cholesterol.

43
Q

What causes the membrane to be more fluid at lower temperatures? How?

A

Cholesterol, by preventing snugly fitting of saturated fatty acid side chains to form gels.

44
Q

Integral Membrane Proteins

A

Possessing one or more hydrophobic regions that exhibit an affinity for the hydrophobic interior of the lipid bilayer. Embedded in and/or extend through the membrane.

45
Q

Peripheral Membrane Proteins

A

Bound to membrane surfaces through weak electrostatic forces and hydrogen bonds. Primary though interactions with integral proteins.

46
Q

What must be used to extract integral membrane proteins from the membranes?

A

Detergents.

47
Q

Transmembrane proteins form either ___ or ___ as they pass through the hydrophobic interior of the membrane.

A

alpha helices, beta barrels.

48
Q

What maximally satisfies the tendency of the hydrophilic polypeptide backbone to form H-bonds?

A

alpha helix and beta barrels.

49
Q

For single-pass alpha helix transmembrane proteins, the ___ side chains are exposed to ___, contacting the ____.

A

hydrophobic, the outside of the helix, hydrophobic lipid tails.

50
Q

For multipass alpha helix or beta barrel proteins, the ___ side chains face the ___, and the ___ side chains face ___.

A

For multipass alpha helix or beta barrel proteins, the hydrophobic side chains face the outside hydrophobic lipid tails, and the hydrophilic side chains face internal hydrophilic environment.

51
Q

What is the plasma membrane reinforced by?

A

The underlying cell cortex

52
Q

What is cell cortex?

A

The animal cell membrane has no cell wall as reinforcement, so it is stabilized by a meshwork of fibrous proteins called the cell cortex.

53
Q

What is the cell cortext attached to?

A

The underside of the membrane via transmembrane proteins.

54
Q

What is spectrin?

A

The main compoent of cell cortex in red blood cells.

55
Q

Spectrin forms the ____ mesh by linking to transmembrane proteins via ___ and ___.

A

cell cortex, actin, attachment proteins.

56
Q

What causes membrane proteins move freely in the membrane?

A

Membrane proteins are linked to cell cortex, therefore cannot move freely in the membrane.

57
Q

Do membrane proteins vary in their mobility?

A

Yes.

58
Q

Membrane proteins have restricted mobility due to what?

A 
Slower than lipids.
Being tethered to: 
1) Cell cortex-cytoskeleton
2) Extracellular matrix (ECM)
3) Proteins of another cell surface.
Diffusion barriers
59
Q

Fluid-Mosaic Model

A

Membranes are composed of a Phospholipid Bilayer with various protein molecules floating around within it. The ‘Fluid’ part represents how some parts of the membrane can move around freely, if they are not attached to other parts of the cell.

BIO353 (8 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions