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Molecular Cell Biology > Chapter 4: The Structure and Function of the Plasma Membrane > Flashcards

Chapter 4: The Structure and Function of the Plasma Membrane Flashcards

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1
Q

What are the functions of the membrane and describe each! (7)

A
  1. compartmentalization - encloses cell boundary and intercellular spaces..each compartment has different contents so specialized activities can occur without interference ..interference = diseases. *Independently regulated.
  2. framework for biochemical rxns- ensures components are arranged for effective interaction
    -ie. all ETC molecules are embedded in MIT M
  3. selectively permeable M - prevents unrestricted exchange of molecules…method of communication (gap junctions in cardiac cells ex)….aquaporins = how water gets into cells.
  4. transport- substances can be moved up or down [ ] gradient…up= expenditure of ATP….establishes ion gradients
  5. signal transduction - bind ligands to M receptors…changes internal cellular activities (2nd messenger) ex: cyclic AMP= common messenger
  6. intercellular interaction - recognition and signalling occurs between cells…ex: immune system!
  7. energy transduction - one type of energy is converted into another~>..example photosynthesis.. Light+sugar
    L> Sugar —>ATP= cellular respiration
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2
Q

Describe the structure of the plasma membrane!

A
  • lipids
  • carbohydrates
  • ratio of lipid to protein in membrane depends on which membrane , which cell and which organization it is in!
  • glycoproteins: carb attached to protein
  • glycolipid : carb attached to lipid
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3
Q

Mitochondrial membrane concentration?

A
  • high [] of protein to lipid!
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4
Q

Neuron membrane concentration?

A
  • high [] of lipid to protein
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5
Q

What is between the inner and outer leaflets? Also what the fuck are inner and outer leaflets? (maybe answer in the reverse order)

A
  • inner leaflet is the phospholipids closest to the inside of the cell…outer is closer to the exterior
  • between them is a hydrophobic region
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6
Q

What are the three membrane lipids?

A
  • phosphoglycerides
  • sphingolipids
  • cholesterol
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7
Q

All lipids that make up a membrane are _____

A
  • amphipathic…have a water loving and hating region!
    O - hydrophilic region
    | \ - hydrophobic region…..
    **they aggregate spontaneously in a membrane
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8
Q

Phosphoglycerides:

- ____ and ___ backbone

A
  • phospholipid and glycerol
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9
Q

Phosphoglycerides:

- What are the four major phospholipids?

A
  1. choline
  2. ethanolamine
  3. serine
  4. inositool
    * phosphatidic acid (base of phospoglyceride)
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10
Q

Phosphoglycerides:

- tail composed of?

A
  • saturated FA and Unsaturated FA
  • unsaturated = membrane fluid = not as compact…ie why there is a bend in the tail!

————————–phosphate
choline |
polar head group —-glycerol backbone |========= fatty chain

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11
Q

The polar head group can vary in phosphoglycerides. What are they? (6)

A
  1. Dioleoyl Phosphatidic acid
  2. Phosphatidic acid
  3. Phosphatidyl-cholne (lecithin) (PC)
  4. Phosphatidyl- serine (PS)
  5. Phosphatidyl-ethanolamine (cephaline) (PE)
  6. Phosphatidyl-inositol (PI)
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12
Q

PC?

A
  • mainly found on the outer leaflet
  • important in cell signalling
  • some viruses can use it to gain entry into the cell
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13
Q

PE?

A
  • found in cell M mainly of platelets
  • important in blood clotting
  • promotes membrane curvature
  • inner leaflet of M = where it is found
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14
Q

PE and PC?

A
  • neutral phsophoglycerides
  • also have EPA ( five double bonds in FA tail) and DHA(6 double bonds in FA tail) aka omega 3’s
    L> FA that lowers cholesterol
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15
Q

PS?

A
  • inner leaflet of PM
  • flippase are enzymes that ensure they are on the right leaflet
  • sign something is wrong if it is on the outer
    L> aka cell is not functioning right
  • prevents memory loss
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16
Q

PI?

A
  • inner leaflet

- cell signalling and emulation of cellular metabolism and growth

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17
Q

Cardiolipin?

A
  • commonly found in the inner mitochondrial membrane
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18
Q

PS and PI have what kind of charge?

A
  • negative
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19
Q

Sphingolipids:

- ceramide molecules??

A
  • sphingosine (sugar) + FA chain

* * sugar containing lipid molecule at the PM surface

20
Q

Sphingolipids are the most or least abundant lipid in PM?

A
  • least
21
Q

Sphingolipids:

- ceramide molecules types?

A
  • Sphingomyelin ( ceramide + phosphorylcholine)
  • Glycolipid (ceramide + CHO)
    L> cerebroside (simple sugar)
    L> ganglioside(cluster of sugars)
22
Q

Sphingolipids

- functions???

A
  • protects PM from harsh exterior …lipid acts a buffer to low pH of other enzymes
  • electrical insulation : insulates axons
  • cell recognition : cell service receptor
  • binds cell to extracellular matrix ..helps it bind so the cell can grow.
23
Q

-Ceramide function?

A
  • cell signalling
  • can be released from PM to act as a signalling molecule for differentiation or proliferation of other cells… Also signal of cell death!
24
Q

Sphingosine functions in?

A

signal transduction in PM

25
Q

Accumulation of Sphingomyelin leads to?

A
  • Niemann pick disease (lysosomal storage disease)
26
Q

Cerebroside?

L> potential disease associated ?

A
  • Gal + ceramide
  • defect in degradation of cerebroside causes organs to malfunction… Gaucher’s disease
    L> Type 1 and 2
    -type can be helped with an enzyme replacement therapy but for type 2 death occurs by age 2.
27
Q

Ganglioside?

A 
- GalNac + Gal + Glu + ceramide 
                   |
               SiA 
- Tay Sachs Disease
L> fatal...build up of lipid in brain...die by age four...homozygous recessive..... 
**GM2
28
Q

Ganglioside:

L> GM1 and GM3?

A
  • GM1
    L> acts as cell surface receptor
    L> influenze, cholera and bothcelism use to gain entry to the cell.
    *cholera attaches to GM1
    L> cyclic AMP (cAMP) increases in intracellular level of it which leads to an increase in sodium and water loss in the large intestine.
    -GM3:
    L> lack of it causes neurological diseases ..blindness…seizures etc
29
Q

Cholesterol:

-__,___ molecules

A
  • flat , rigid
30
Q

Cholesterol:

-interfere with the movement of?

A 
- FA tails...
when present they are not as tightly as packed...making them more fluid 
0
|\ 
| <== cholesterol stiffened region
31
Q

Plasma Membrane fluidity:

- is affected by?(3)

A
  • number of double bonds in FA tails..
  • FA chain length
  • cholesterol
    Fluid= more double bonds, short FA tails and less cholesterol….. stiff= less double bonds, long FA tails and more cholesterol.
32
Q

Plasma Membrane fluidity:

- Transition temperature?

A
  • the temp where the membrane movement becomes restricted
33
Q

What is a micelle?

A
  • bubble or sphere of phospholipids

L> FA tails are in the interior of it~…interior= hydrophobic

34
Q

what is a liposome?

A
  • double layer (lipid bilayer)
  • sphere shape
  • inner sphere is hydrophilic
35
Q

Discuss the spontaneous self assembly of M lipids!

A
  • single layers= micelle
  • bilayer = liposome
  • liposomes are used to deliver drugs/DNA
    L> PROBLEM?
    L> drug couldn’t get into the cell…our immune system in the BS detects it before its contents could be delivered (1st Gen liposomes)
  • 2nd Gen liposomes = stealth liposomes
    L> protective layer of polyethylene glycol (low toxicity)
    L> antibody in outer membrane ( for cell-cell recognition…aid in reaching the target cell)
    L> within the hydrophobic region= lipid soluble drug in bilayer..
    L> drug crystallizes in aqueous form in the hydrophilic region.
36
Q

Membrane CHO’s :

- ___ or ___

A

glycolipids

glycoproteins

37
Q

Membrane CHO’s :

- they are on the non-______ membrane side

A
  • cytosolic

aka carbohydrate is on the outside of the PM but if in the mitochondria it will be in the inside not in the cytosol!

38
Q

Membrane CHO’s :

- ___ composition and structure

A
  • varied
39
Q

Membrane CHO’s :

- specificity with respect to ?

A
  • molecular interactions
    ex: blood….. they have different terminal modifications for O, A and B antigens…
  • o enzyme is not working and AB have enzymes that modify to have both antigens
40
Q

Membrane CHO’s :

- membrane is composed of ___% glycolipids and ___% glycoproteins.

A

10

90

41
Q

Membrane CHO’s :

- what is the most complex process that can go on?

A
  • addition of carb to a protein
    L> important role in cell-cell interactions
    L> sorting of membranes into different compartments.
42
Q

Membrane Proteins:

- three types

A
  1. Integral proteins
    L> transmembrane aka they go through the membrane completely and if pulled out they would disrupt the membrane.
  2. Peripheral proteins
    L> outside the lipid bilayer
    L>mobile protein
    L> if pulled out it will not disrupt the M
  3. Lipid-anchored proteins
    L> covalently linked to a lipid in the M bilayer
    L> GP1- glycophosphatidyl inositol
    L>main function: adhesion…aka other cells to base membrane…in cancer these are not maintained i.e. metastasizing ..or they are completely removed.
43
Q

Function of M-proteins:

  • Integral
  • Peripheral
  • Lipid-anchored
A
  • receptors, channels, agents in ETC, enzymes
  • anchors, glycocalyx(cell coat), factors in transducing signals, enzymes
  • receptors, cell adhesion and enzymes
44
Q

Dynamic Nature of the PM?

i.e. human and mouse example

A
  • human cell+ addition of sendai (fusing virus regardless of species)
  • mouse cell
  • two cells fuse
    -after 40 mins
    the proteins have completely mixed up…its no longer half and half…
45
Q

Three membrane sections?

A
  • apical plasma membrane (free end of cell)
    L> regulation of nutrient and water intake
    L>regulated secretion
    L> protection
  • lateral plasma membrane
    L> cell contact and adhesion
    L> cell communication
  • Basal membrane
    L> cell substratum contact
    L> generates ion gradients….base membrane
46
Q
  • hypotonic solution +cell?
  • hypertonic solution + cell?
  • isotonic solution + cell?
A
  • net water gain..cell swells (taking in water)
  • net water loss…cell shrinks (giving up solutes)
  • no net loss or gain

Molecular Cell Biology (6 decks)

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