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C Bio > PM Part 1 (16) > Flashcards

PM Part 1 (16) Flashcards

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Biology 101 flashcards
1
Q

what does the PM distinguish?

A

exterior & life

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2
Q

what makes the PM dynamic?

A

capable of fusing without losing continuity

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3
Q

external membrane

A

PM encloses the entire contents of the cell

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4
Q

internal membrane

A 
Nuclear envelope
Mitochondrial membranes 
Chloroplast membranes
Lysosomal membrane
ER
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5
Q

what are functions of membranes?

A

Compartmentalization
Eukaryotes
Defines diff functions of the cell

Site of biochemical activities
Scaffolding of PROs
Chloroplasts –> photosynthesis facilitated by integral PROs

Selectively permeable membrane

Transporting solutes (proton pump)
	Creates gradients

Responding to external signals
Intercellular interaction
Cell-to-cell attachment & communication

E transduction
Ion gradients enable production of ATP

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6
Q

what is the membrane permeable to?

A

lipids

steroids

O2 & CO2 (gas)

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7
Q

what is the membrane impermeable to?

A

water soluble compounds

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8
Q

what do membranes consist of?

A

polar lipids in a bilayer

PROs

CARBs

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9
Q

fluid mosaic model

A

fluid composition of lipids, carbs & PROs

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10
Q

How do PROs appear in the fluid mosaic model?

A

discontinuous particles

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11
Q

how do the interactions occur in the fluid mosaic model?

A

transient interactions

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12
Q

what is the evidence of the fluid mosaic model?

A

2 cells with diff dye fused together

the combined cell had the dyes dispersed –> move freely

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13
Q

how do you fuse cells?

A

electric shock

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14
Q

what lipids are found in the cell membrane?

A

o Phosphoglycerides
o Sphingolipids & Glycolipids
o Cholesterol

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15
Q

diglyceride

A

one saturated & one unsaturated FA

straight chain

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16
Q

3rd OH group is coupled to a phosphate plus either

A

Choline – phosphatidyl choline

Ethanolamine – phosphatidylethanolamine

Serine – phosphatidylserine

Inositol – phosphatidylinositol

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17
Q

Sphingosine

A

amino alcohol with a long hydrocarbon chain

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18
Q

role of sphingolipids

A

membrane structure, decreases fluidity making it more gel-like –> provides resistance to stressors

signaling & cell membrane recognition with glycolipids

Tighter packing since only one FA chain is attached

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19
Q

glycolipids play a role in

A

Cell membrane recognition

Electrical conduction (ex: myelin around nerve cells)
Rigidity provides insulated properties
Myelin sheath acts as an insulator

Inter-cell communication

Binding bacterial toxins (ex: botulism) & some viruses permitting their entrance into the cell
Enable bacteria to target the glycolipid to infect us

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20
Q

what type of cells is cholesterol absent in?

A

bacteria

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21
Q

What type of cholesterol is in plant cells?

A

phytosterol

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22
Q

how does cholesterol effect lipids at high temp?

A

reduces membrane fluidity

Fills gaps b/w phospholipids preventing them from becoming too fluid

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23
Q

how does cholesterol effect lipids at low temp?

A

helps prevent membranes from freezing, increases fluidity

When lipids become too compact the cholesterol creates spaces b/w the molecules 

Lipids composition changes, creating more unsaturated bonds creating more bends in the chains  not as compact
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24
Q

fluidity/viscosity

A

measure of freedom of movement within the membranes

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25
Q

why is fluidity important? & When is it relevant in cell processes?

A

mobility & organization (moving PROs)

cell growth
cell division
inter-cell junctions
endocytosis & vesicle traffic

26
Q

heterogeneity

A

local patches of membrane may have unique fluidity

27
Q

exs of heterogeneity

A

sphingolipid rich particles

cholesterol on lipid rafts

28
Q

what is fluidity dependent on?

A

type of lipid & temperature

29
Q

lipid rafts

A

region of the PM rich in sphingolipids & cholesterol

aggregates of PROs of the same function

30
Q

what lipids aren’t amphipathic

A

glycolipids & cholesterol

31
Q

desaturase

A

remodeling enzyme, alters FA chains, increases the number of double bonds

32
Q

when does the cell increase the amount of desaturase?

A

cold conditions

33
Q

acetyl transferase

A

moves FAs b/w glycerol & attaches them to a new spot

Used to alter PM triglycerides to maintain correct fluidity

34
Q

phospholipase

A

splits FA from the glycerol backbone

Used to alter PM triglycerides to maintain correct fluidity

35
Q

how is membrane fluidity altered?

A

Remodeling enzymes for short-term response when temperature changes
Increase the amount of desaturase (converts FA saturated chains to unsaturated chains)
Presence of double bonds = increase in kinks = increases fluidity

Shuffling of FAs on phospholipids
Phospholipase: splits FA from glycerol backbone
Acetyltransferase: moves FAs b/w glycerol & attaches them to a new spot
Saturated –> unsaturated to increase fluidity

36
Q

what type of cells remodel their PMs?

A

prokaryotes & eukaryotes

37
Q

what is an ex of an animal modifying its PM composition?

A

hibernating animals

increase fluidity of membranes

38
Q

what maintains lipid composition on opp sides of the membrane?

A

Flippases & other PROS that move lipids from one side to the other

PROs that modify polar heads

lipid transport PROs that transport lipids through the cytoplasm

39
Q

why is membrane lipid asymmetry important?

A

diff lipids provide durability on each side providing –> can withstand physical stresses better

40
Q

which way to most carbs face on membranes?

A

outward into the extracellular space

41
Q

what organelle’s membrane carbs don’t face outwards? & why

A

lysosomes

lipids point inwards protecting lumen from digestive enzymes

42
Q

how are carbs assoc with the membrane?

A

glycoPROs

Glycolipids

43
Q

glycoPROs

A

short, branched oligosaccharides
Play roles in cell interactions
Attached to the R-group of: Asparagine (N-linked) or Serine or Threonine (O-linked)

44
Q

glycolipids roles

A

Provide tags to invaders (infectious diseases)

Identify cell types (ex: blood type)

45
Q

What percentage do PROs, lipids & carbs have in the PM?

A

52% PRO

40% lipid

8% carb

46
Q

glycocalyx

A

dense mass of glycoPROs on the cell surface protecting cells against abrasions & involved in cell signaling

47
Q

what role does glycocalyx serve in the gut?

A

protective function against digestive enzymes

48
Q

what role does glycocalyx serve in bacteria?

A

outer coating of the cell wall

49
Q

what type of interactions does glycocalyx have?

A

receptor/ligand interactions

50
Q

integral PRO

A

lipid soluble portion, cytosolic portion & exterior portion

51
Q

peripheral PROs

A

inside or outside the membrane, assoc with non-covalent bonds

52
Q

lipid anchored PROs

A

inside or outside, covalently linked to a lipid

53
Q

what are the 3 classes of membrane PROs?

A

integral PROs

peripheral PROS

lipid-anchored PROs

54
Q

what type of AAs are in the transmembrane portion of integral PROs? & what is its conformation?

A

hydrophobic or non-polar AAs

alpha helical

55
Q

how do we determine what AAs are found in the transmembrane portion of an integral PRO?

A

hydrophobicity plot

56
Q

how do peripheral membrane PROs attach to the membrane?

A

Bind to hydrophilic portion of phospholipids or

a hydrophilic portion of an integral PRO

57
Q

what is the role of peripheral membrane PROs on the cytoplasmic side?

A

transmembrane signal transduction

58
Q

what’s a major diff among lipid-anchored membrane PROs & peripheral membrane PRos?

A

lipid-anchored –> covalently bonded

peripheral –> non covalent

59
Q

what are the types of lipid anchors?

A

Lipid + carb (ex: glycosol phosphatidyl linked PRO) in the outer leaflet
or
long hydrocarbon chain in the inner leaflet

60
Q

what is the role of lipid-anchored membrane PROs?

A

cell signalling or adhesion

C Bio (30 decks)

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