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BMS242 Cell and Molecular > L24 - Vesicular Transport > Flashcards

L24 - Vesicular Transport Flashcards

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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
Once in the early endosome describe what happens to LDL
Fusion with the lysosome | LDL broken apart and free cholesterol is produced
26
Once in the early endosome describe what happens to the receptor
Recycled to the membrane in transport vesicles
27
What disease can defective endocytosis cause
Atherosclerosis
28
Describe how mutations can cause atherosclerosiss
Mutation blocks formation of the coated pit by preventing the actiion of adaptor proteins Acculation of lipoporteins - formation of plaques
29
What do adaptor molecules also bind
PIP2 ligand recruiting clathrin to form vesicles
30
What is phosphatifylionsitol is a minor ______________ but a major ________________
Minor component of the membrane | Major signalling lipid
31
Where is phosphatidylinosityl located What is it the target of What is the action when activated
On the inner leaflet PI kinases Phosphorylation of the inositol sugar
32
What is the structure of the clathrin
Tri-legged triskelia
33
Describe the role of dynamin
Pinches - invagination to form a vesicle GTPase Gets its energy from thee hydrolysis of GTP
34
What is protein similar to clathrin used by the ER
COPII
35
What is protein similair to clathrin used by the Golgi
COPI
36
What compartment uses clathrin
The plasma membrane
37
What is phagocytosis an example of
Vesicle formation which does not require clathrin
38
Phagocyres use what to forms pseudopods
Actin driven membrane invagination
39
Phagocytes form and extend ___________
Pseudopods
40
Phagosome fuses with the lysosome to form the
Phagolysosome
41
What does the the lysome contains
Acid hydrolases
42
What is the role of actin in phagocytosis
Actin makes up the insdie of the pseudopods which extend around the material to be phagocytosed
43
What does autophagy allow
The elimination of malfunctioning organelles
44
Describe the process of autophagy
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
What is the fundamental barrier to the fusion of two membranes
Repulsion from both - two negative charges
46
Exocytosis is responsible for
Secretion of hormones and digestive enzymes | Recycling of plasma membrane receptors and neuronal communication
47
What are the two types of exocytosis
COnsitiutive and regulated
48
Describe constiutive exocytosis
cont. secretion of material
49
Describe regulated exocytosis
Secretion in response to a sstimuli
50
What type of exocytosis is used in the secretion of insulin
Regulated | Release of insulin from b-islet cells only happens in response
51
What is the role of SNARE proteisn
Overcome the repulsion of negatively charged membranes
52
v-SNARE
Vesicular SNARE
53
vAMP
Vesicle associated membrane protein
54
What are the two vSNAREs
vAMP and synaptobrevin
55
t-SNARE
target membrane SNARE
56
What are tSNAREs
Syntaxin | SNAP25
57
How many helicies does SNAP25 contribute
Two helicies
58
Describe how a coiled coil forms
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
What enzyme catalyses the disociation of SNARES, what does this require
NSF enzyme | Hydrolysis of ATP
60
What is the target of botulinum neurotoxin
SNARE proteins
61
Botulism happens upon
Consumption of contaminated foods
62
Tetanus could occur
Due to skin cuts during childbirth or dirty needle injections
63
Describe what normally happens at synapses
Synaptic veiscle containing synaptobrevin fusing with the PM containing syntaxin and SNAP-25
64
Describe the effect on bot. neurotxoin on the synapse
Attacks and cleaves the SNARE protein preventing vesicle fusion CLEAVES SNAP-25 - COILED COIL UNABLE TO FORM PROPERY
65
Describe the method of botox
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
How long does Botox last for
Until the enzymes have been resynthesised - leading to the full resumption of neuronal transmission
67
What are the medical uses of botox Upon what principle does it work on
Spasm, systonia and in cosmetic medcine Local muscle paralysis
68
What does Botox cleave
SNAP25

BMS242 Cell and Molecular (26 decks)

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