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Bio*1090 Part 2 Flashcards > Lecture 15 > Flashcards

Lecture 15 Flashcards

1
Q

Function of Biological Membranes

A

1) Define Cell Boundary
2) Define Enclose Compartments
3) Control Movement of Material into and out of the Cell
4) Allow Response to External Stimuli
5) Enable interactions between cells
6) Provide Scaffold for biochemical

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2
Q

What does a muscle cell contain?

A

A plasma membrane, and sarcoplasmic reticulum

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3
Q

Why are red blood cells useful as a model for studies of membrane structures?

A

They do not contain nuclei or internal membranes

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4
Q

What is the plasma membrane?

A

A trilaminar (three layer) structure made of a phospholipid bilayer

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5
Q

How thick is the plasma membrane?

A

6nm

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6
Q

What do lipid molecules do?

A

Spontaneously aggregate to bury their hydrophobic tails in the interior and expose their hydrophilic heads too water.

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7
Q

What is a micelle formed by?

A

Fatty acids with only one hydrophobic chain.

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8
Q

What are phospholipids?

A

Amphipathic, which means they have both hydrophobic (non-polar) and hydrophilic (polar) regions.

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9
Q

What part of the phospholipid is polar?

A

Hydrophilic Head

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10
Q

What part of the phospholipid is non polar?

A

Hydrophobic tail

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11
Q

Hydrophilic

A

A molecule attracted to water molecules

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12
Q

Hydrophobic

A

A molecule not attracted by water

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13
Q

What do phospholipids consist of?

A

Two fatty acyl molecules, glycerol backbone and phosphate residue

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14
Q

What positions are the fatty acids, glycerol and phosphate on?

A

Fatty Acids: sn-1 and sn-2 positions of glycerol

Head group linked by phosphate residue at the sn-3 position.

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15
Q

Where does phospholipids making the plasma membrane come from?

A

Synthesis occurs at the interface of the cytosol and outer endoplasmic reticulum membrane, which has all the enzymes for synthesis.

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16
Q

1st Step of Phospholipid synthesis?

A

In the cytosol, fatty acids are activated by the attachment of a CoA molecule

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17
Q

2nd Step of Phospholipid Synthesis?

A

The activated fatty acids bond to glycerol-phosphate and are inserted into the cytosolic leaflet of the ER membrane via acyl transferase

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18
Q

3rd Step of Phospholipid Synthesis

A

The phosphate is removed by a phosphatase enzyme

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19
Q

4th Step of Phospholipid Synthesis

A

A choline already linked to phosphate is attached via choline phosphotransferase

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20
Q

5th Step of Phospholipid Synthesis

A

Flippases transfer some of the phospholipids to the other leaflet.

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21
Q

What is the final step of Phospholipid Synthesis

A

A vesicle will come off from the ER containing phospholipids for the cytoplasmic cellular membrane on its exterior leaflet and phospholipids for the exoplasmic cellular membrane on its inner leaflet.

22
Q

Fluid

A

Individual lipid molecules move

23
Q

Mosaic

A

Diverse ‘particles’ like proteins, carbs, and cholesterol penetrate the lipid layer

24
Q

What is the plasma membrane viewed as?

A

Two-dimensional liquid that restricts the diffusion of membrane components

25
Q

What is embedded in the plasma membrane?

A

Different proteins, that can interact and are mobile

26
Q

What are the dynamics of the plasma membrane?

A

Lipids move easily, laterally within leaflet

Lipids movement to other leaflet is difficult and slow

27
Q

Membrane proteins diffuse within the bilayer:

A
  • Movement of proteins is restricted
  • Rapid movement is spatially limited
  • Long range diffusion is slow
  • Biochemical modification can alter protein mobility in the membrane
28
Q

What is the Frye-Edidin Experiment

A

Just after the fusion. of the two cells, the surface proteins are segregated, but after a short period of time, the surface proteins of both cells diffuse around the unified membrane and mingle

29
Q

What properties do all membrane share?

A

Approximately 6nm thick

Stable, flexible and capable of self assembly

30
Q

What does the inner membrane of mitochondria contain?

A

A very high concentration of protein necessary for electron transport chain and ATP synthesis

31
Q

What does myelin sheath consist of?

A

Layers of plasma membrane wrapped around a neurons axon.

32
Q

What are the three types of proteins?

A

Integral, Peripheral, and lipid-anchored

33
Q

Integral Proteins

A

Membrane proteins that span the lipid bilayer (are inside)

34
Q

Peripheral Proteins

A

Membrane proteins associated with the surfaces of the lipid bilayer

35
Q

Lipid Anchored Proteins

A

Proteins that attach to a lipid in the bilayer

36
Q

What are the functions of integral proteins?

A

1) Transport of nutrients and ions
2) Cell-Cell Communication
3) Attachment

37
Q

What are biological membranes?

A

Asymmetrical

38
Q

What does the outer leaflet contain?

A

Glycolipids and glycoproteins

39
Q

What does temperature affect?

A

The fluidity of biological membranes

40
Q

What does warming do?

A

Increases fluidity

41
Q

What does cooling do?

A

Decreases fluidity

42
Q

What is membrane fluid determined by?

A

The nature of the lipids in membrane

43
Q

What do unsaturated lipids do?

A

Increases fluidity

44
Q

What do unsaturated lipids do?

A

Reduce fluidity

45
Q

In responses to change in temperature, lipid composition of membranes can be changed by:

A

1) Desaturation of lipids
2) Exchange of lipid chains

46
Q

What does balance between ordered and disordered structure allow?

A
  • Mechanical support and flexibility
  • Membrane assembly and modification
  • Dynamic interactions between membrane components (Proteins can come together reversibly)
47
Q

What does cholesterol modulate?

A

Membrane fluidity

48
Q

What does cholesterol act as?

A

A bidirectional regulator of membrane fluidity
- High temperatures, it stabilizes the membrane and raises its melting point
- Low temperatures, it intercalates between phospholipids and prevents them from stiffening

49
Q

If cholesterol is added to a liquid crystal membrane:

A

Fluidity will decrease

50
Q

If cholesterol is added to a crystalline gel membrane:

A

Fluidity will increase

51
Q
A

Bio*1090 Part 2 Flashcards (3 decks)

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