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EOM 1 - Test 1 > Lecture 11: Biomembranes > Flashcards

Lecture 11: Biomembranes Flashcards

Biomembranes

1
Q

What are four basic features of biomembranes?

A
  1. Phospholipid Bilayer
  2. Embedded Proteins
  3. Non Covalent Membranes (fluidity)
  4. Membrane Flexibility
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2
Q

What form are most of the carbohydrates in biomembranes?

A

Glycoproteins or Glycolipids

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3
Q

What are molecules w/both hydrophobic and hydrophilic regions?

A

Amphipathic

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4
Q

If the cross sectional area of the polar group is greater than that of the acyl side chain, what is likely to form?

A

Micelles

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5
Q

What causes liposomes to form spontaneously?

A

the unstable edges of the lipid bilayer

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6
Q

What are the most abundant lipids in cell membranes?

A

Phospholipids

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7
Q

What is the general structure of phospholipids?

A

Phosphate (polar head) + Glycerol + Hydrocarbon Chains of the Fatty Acid (non polar)

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8
Q

These lipids contain sphigosine.

What is sphingosine?

What is an example found in the neuron?

A

Sphingolipids

Amino-alcohol

Sphingomyelin

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9
Q

This amphipathic sterol is vital for regulation of the biomembrane’s fluidity.

A

Cholesterol

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10
Q

What are the major phospholipids found on the outer leaflet?

A

phosphatidylcholine

sphingomyelin

glycolipids

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11
Q

What are the major phospholipids found on the inner leaflet?

A

phosphatidylethanolamine

phosphatidylserine

phosphatidylinositol

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12
Q

Do all membranes have a uniform distribution of lipids?

A

No, different membranes have unique lipid distributions

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13
Q

What is the general process for generating lipid bilayers in lab?

A
  1. Treat w/organic solvent
  2. Remove insoluble protein, oligosaccharide residues
  3. Evaporate solvent
    4a. Rehydrate in water
    4b. Rehydrate in water w/planar bilayer
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14
Q

Why is the study of liposomes relevant for disease?

A

Artificially constructed liposomes can be filled with drugs and used as a delivery system in the treatment of disease

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15
Q

Why are individual lipids able to diffuse laterally rapidly?

A

The bilayer is held together by noncovalent forces

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16
Q

What is the result of low Temp on a phospholipid bilayer?

A

Gel-like consistency

Less Fluid

Thicker diameter

17
Q

What is the result of high Temp on a phospholipid bilayer?

A

Fluid-like consistency

More Fluid

Thinner diameter

18
Q

How is membrane fluidity regulated?

A

Altering membrane composition (proteins, cholesterol, etc)

19
Q

What affect does Cholesterol have on the bilayer in high and low T?

What is this termed?

A

High: Decreased membrane fluidity; attraction to cholesterol pulls them closer

Low: Increased membrane fluidity; increase distance between phospholipids

Paradoxical

20
Q

What is the effect of fatty acyl chain saturation on fluidity?

How could this be manipulated?

A

Saturated: Easier to pack, less fluid

Unsaturated (kinked): Harder to pack, more fluid

You could use a desaturase enzyme to decrease fluidity (or vise versa)

21
Q

What is the effect of fatty acyl chain length on fluidity?

How could this be manipulated?

A

Longer Tail: Less Fluid

Shorter Tail: More Fluid

You could use an enzyme to alter tail length

22
Q

What are localized regions of the membrane enriched with cholesterol, sphingolipids, and saturated phospholipids called?

What important class of glycoproteins are found here?

Why are they important?

A

Lipid rafts

GPI-anchored proteins

Lipid rafts and ^ likely play a role in signal transduction

23
Q

What does phospholipid synthesis occur?

What ensures even growth of both halves of the lipid bilayer?

A

The cytostolic surface of the Endoplasmic Reticulum (ER) membrane

Lipid translocators called Flippases

24
Q

How to phospholipids reach their final membrane destination?

Are they static during their journey?

What are formed while passing through Golgi apparatus?

A

Membrane trafficking via budding off and fusing

No, they are modified in other cellular compartments, example sphingomyelins and glyolipids are formed as vesicles pass through Golgi Apparatus

25
Q

What lipids are localized mainly on the extracellular leaflet?

What lipids are localized mainly on the cytostolic leaflet?

What does this MX require?

What lipid may play a role in apoptosis signaling?

A

Extracellular: phosphatidylcholine, sphingomyelin

Cytostolic: phosphatidylathanolamine, phosphatidylserine

Energy

Movement of phosphatidylserine to external surface for signaling with macrophages

26
Q

As vesicles bud and fuse during traficking, what is the result of the faces (direction) of the membranes?

A

They are conserved

27
Q

Describe uncatalyzed movement of phospholipids.

A

Lateral diffusion = fast (microseconds)

Transbilayer = slow (days)

28
Q

Describe catalyzed movement of phospholipids.

What do these require?

What catalyzed movement does not require the answer above?

A

Flippases/Floppases move lipids transbiolayer

They require ATP

Scramblases move along a concentration gradient, and do not require energy

29
Q

What are the two major classes of membrane proteins?

How are these bound?

What would be the result of removing these from the bilayer?

A

Integral - covalent - bilayer destruction

Peripheral - non-covalent - no disruption to bilayer

30
Q

What are the two structures of transmembrane proteins?

A

Most are alpha-helices composed of hydrophobic residues; if zig zag across will have both residues

Beta barrels are less common, but form porins for small molecules to transverse; found in mitochondria and some bacteria

31
Q

How are integral proteins attached to the plasma membrane?

What are three major locations and respective methods for these?

A

Lipid Anchors

Cytoplasmic - single covalent linkage between fatty acid acyl chain and N-terminal glycine in protein

Cyostolic - thioester bond between thiol group in cystein near c-terminus of peptide and hydrocarbon anchor

Exoplasmic - complex glycosylated phospholipid linked to C-terminus of protein; GPI example

32
Q

What are two experimental methods for evidence of protein mobility?

A

Human-Mouse Cell Hybrid

Label-Laser-Measure Experiment (quantitative)

33
Q

What conditions limit protein mobility?

A 
Protein-Protein interaction in membrane (self)
Adjacent cell protein (other)
Cytoskeletal interactions (in-cell)
Extracellular interactions (out-cell)
34
Q

What is the importance of membrane glycoproteins?

What is glycocalyx?

A

Cell-to-cell recognition; such as selectin binding with oligosaccharides in the inflammatory response of would healing

Glcocalyx is the carbohydrate coating of the outer surface which extends into the extracellular space

EOM 1 - Test 1 (16 decks)

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