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BMS242 Cell and Molecular > L24 - Vesicular Transport > Flashcards

L24 - Vesicular Transport Flashcards

1
Q

Endocytosis allows

A

Capture of molecules from the outside

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2
Q

Exocytosis allows

A

The secretion of molecules from the inside

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3
Q

What are the three major components of the PM

What are the roles of each

A

Lipids - continutiy and flexibility
Proteins - traverse the membrane and have functions in transport
Carbohydrates - cell protection and tagging

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4
Q

Describe what happens at the PM in a harsh environment

A

Harsh environment the carbohydrates form a protective layer round the cell

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5
Q

What are the three phospholipids in the membrane

A

Ehtanolamine
Serine
Choline

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6
Q

What is the most common PL in the membrane

A

Choline

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7
Q

What is the PL which has an overal negative charge

A

Serine

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8
Q

Why must the membrane contain unsaturated PLs

A

To provide flexibility

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9
Q

What sort of bonds are present in unsaturated hydrocarbons

A

C=C // Cis
Cause a kink in the chain
Prevent the phospholipids from packing so tightly

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10
Q

Describe omega 3 fatty acids

A

Contains a cis double bond at carbon 3

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11
Q

Where are omega 3 fatty acids produced

A

Sea plants

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12
Q

Describe omega 6 fatty acids

A

COtnain a double bond at carbon 6

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13
Q

Where are omega 6 fatty acids produced

A

Land plants

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14
Q

What is the role of cholesterol in the plasma membrane

A

Helps to seal the membrane making the barrier very tight

Stabilises the membrane

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15
Q

Describe the strucutre of cholesterol

A

OH group

Polar head group

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16
Q

What is the composition of cholesterol

A

17%

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17
Q

What is significant about the inside of the membrane

What is the relevance of this

A

Negatively charged

Most IC molecules and veiscles are negatively charged and thus are repulsed by each other and the membrane

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18
Q

What are the two reasons why phosphatidyl serine is exclusively found on the intracellular leaflet

A

To keep the inside leaflet negatively charge

PLserine trafficked to the otuer leaflet when apoptosis is to be triggered

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19
Q

Two types of membranes associated with the membrane

A

Transmembrane protein

Peripheral proteins

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20
Q

What carries cholesterol in the blood

A

Low density lipoprotein

LDL

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21
Q

What binds to the IC domain of the LDL recepotr … what does this cause the recruitment of … what does this aid

A

Adaptin

Recruits clathrin

Aids with the invagination

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22
Q

What causes the dissociation of LDL from its receptor

A

Low pH of the early endosome

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23
Q

Why is the pH of the early endome so low

A

Proton pump

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24
Q

What is Cholesterol taken up by

A

Receptor mediated endocytosis

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25
Q

Once in the early endosome describe what happens to LDL

A

Fusion with the lysosome

LDL broken apart and free cholesterol is produced

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26
Q

Once in the early endosome describe what happens to the receptor

A

Recycled to the membrane in transport vesicles

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27
Q

What disease can defective endocytosis cause

A

Atherosclerosis

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28
Q

Describe how mutations can cause atherosclerosiss

A

Mutation blocks formation of the coated pit by preventing the actiion of adaptor proteins
Acculation of lipoporteins - formation of plaques

29
Q

What do adaptor molecules also bind

A

PIP2 ligand recruiting clathrin to form vesicles

30
Q

What is phosphatifylionsitol is a minor ______________ but a major ________________

A

Minor component of the membrane

Major signalling lipid

31
Q

Where is phosphatidylinosityl located
What is it the target of
What is the action when activated

A

On the inner leaflet
PI kinases
Phosphorylation of the inositol sugar

32
Q

What is the structure of the clathrin

A

Tri-legged triskelia

33
Q

Describe the role of dynamin

A

Pinches - invagination to form a vesicle
GTPase
Gets its energy from thee hydrolysis of GTP

34
Q

What is protein similar to clathrin used by the ER

35
Q

What is protein similair to clathrin used by the Golgi

36
Q

What compartment uses clathrin

A

The plasma membrane

37
Q

What is phagocytosis an example of

A

Vesicle formation which does not require clathrin

38
Q

Phagocyres use what to forms pseudopods

A

Actin driven membrane invagination

39
Q

Phagocytes form and extend ___________

A

Pseudopods

40
Q

Phagosome fuses with the lysosome to form the

A

Phagolysosome

41
Q

What does the the lysome contains

A

Acid hydrolases

42
Q

What is the role of actin in phagocytosis

A

Actin makes up the insdie of the pseudopods which extend around the material to be phagocytosed

43
Q

What does autophagy allow

A

The elimination of malfunctioning organelles

44
Q

Describe the process of autophagy

A

Small vesicles fuse around the defective organelles
Fusion of more and more vesicles until organelle is internalised in an autphagosome
Fusion with the lysosome

45
Q

What is the fundamental barrier to the fusion of two membranes

A

Repulsion from both - two negative charges

46
Q

Exocytosis is responsible for

A

Secretion of hormones and digestive enzymes

Recycling of plasma membrane receptors and neuronal communication

47
Q

What are the two types of exocytosis

A

COnsitiutive and regulated

48
Q

Describe constiutive exocytosis

A

cont. secretion of material

49
Q

Describe regulated exocytosis

A

Secretion in response to a sstimuli

50
Q

What type of exocytosis is used in the secretion of insulin

A

Regulated

Release of insulin from b-islet cells only happens in response

51
Q

What is the role of SNARE proteisn

A

Overcome the repulsion of negatively charged membranes

52
Q

v-SNARE

A

Vesicular SNARE

53
Q

vAMP

A

Vesicle associated membrane protein

54
Q

What are the two vSNAREs

A

vAMP and synaptobrevin

55
Q

t-SNARE

A

target membrane SNARE

56
Q

What are tSNAREs

A

Syntaxin

SNAP25

57
Q

How many helicies does SNAP25 contribute

A

Two helicies

58
Q

Describe how a coiled coil forms

A

Two a helicies that could around each other
One side of each helix is alpiphatic, one side is poalr
Makes each helix amphipathc
Corresponding regions align

59
Q

What enzyme catalyses the disociation of SNARES, what does this require

A

NSF enzyme

Hydrolysis of ATP

60
Q

What is the target of botulinum neurotoxin

A

SNARE proteins

61
Q

Botulism happens upon

A

Consumption of contaminated foods

62
Q

Tetanus could occur

A

Due to skin cuts during childbirth or dirty needle injections

63
Q

Describe what normally happens at synapses

A

Synaptic veiscle containing synaptobrevin fusing with the PM containing syntaxin and SNAP-25

64
Q

Describe the effect on bot. neurotxoin on the synapse

A

Attacks and cleaves the SNARE protein preventing vesicle fusion

CLEAVES SNAP-25 - COILED COIL UNABLE TO FORM PROPERY

65
Q

Describe the method of botox

A

Botulinum binds first go gangliosides on neuronal membranes
Then enters the luminal space
Following endocytosis one subunit (SNARE protease) escapes the vesicle enters the synaptic cytosol and cleaves SNARE prtoein
Cleaves SNARE cant support fusion
BLOCKADE OF NEUROTRANSMISSION

66
Q

How long does Botox last for

A

Until the enzymes have been resynthesised - leading to the full resumption of neuronal transmission

67
Q

What are the medical uses of botox

Upon what principle does it work on

A

Spasm, systonia and in cosmetic medcine

Local muscle paralysis

68
Q

What does Botox cleave

BMS242 Cell and Molecular (26 decks)

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