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Molecular cell > endomembrane system continued > Flashcards

endomembrane system continued Flashcards

1
Q

endosomal compartment

A

endosomal compartments are temporal sorting stations where the fate of endocytosed cargo is determined.

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2
Q

endosomal compartment is the same as

A

ENDOSOMES

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3
Q

which pathway are endosomal compartment part of

A

the endocytic cycle

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4
Q

how many types of endosomes are involved in processing endocytosed material and what are their names

A

3: early endosomes, recycling endosomes, late endosomes

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5
Q

membrane trafficking along the endocytic pathways

A

1) formation of a vesicle at the plasma membrane
2) fusion of vesicle with early endosome
3) decision: degradation or recycling?
4) recycling via recycling endosome
5) maturation of early endosome to late endosome
6) recycling from late endosome to golgi
7) maturation of lat endosome into lysosome

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6
Q

what is membrane trafficking

A

Membrane trafficking is the process by which proteins and other macromolecules are distributed throughout the cell, and released to or internalised from the extracellular space. Membrane trafficking uses membrane-bound vesicles as transport intermediaries.

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7
Q

what occurs to pH during maturation in the endosomal compartment

A

it decreases from 6.5 to 4.5

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8
Q

late and early endosomes can be distinguished because

A

they look different (early is much rounder)

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9
Q

EE

A

early endosome

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10
Q

LE

A

late endosome

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11
Q

recycling can occur in three ways:

A

1) straight from the early endosome and out of the cell
2) from he early endosome to the golgi and then out the cell
3) from the late endosome to the golgi and out of the cell

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12
Q

lysosomal compartment

A

also known as vacuole

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13
Q

what do lysosomes serve as

A

disposal containers

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14
Q

how does the pH in a lysosomes help serve their purpose

A

it is much lower than the rest of the cell (pH of 5 instead of 7)

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15
Q

what occurs in the the lysosome

A

acid hydrolases (proteases, lipase)

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16
Q

in order to reach the pH in the lysosome what is used

A

a H+ ATPase pump to create optimum pH for acid hydrolases

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17
Q

lysosomes ar known as ……. in plant and fungi cells

A

vacoule

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18
Q

lysosomes are much …. than vacoules

A

smaller compared to the cell size

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19
Q

hydrolases

A

chop proteins and lipids up into building blocks to be reused

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20
Q

three pathways that degrade lysosomes

A

1) phagocytosis
2) pinocytosis
3) autophagy

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21
Q

phagocytosis

A

in macrophages, cleans the body from invading pathogens and damaged cells. some pathogens stop the process and escape the phagocyte

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22
Q

incomplete phagocytosis

A

underlies the endosymbiont hypothesis

23
Q

endosymbiont hypothesis

A

concerns the origin of mitochondria and chloroplast–> according to this hypothesis, these organelles originated as separate prokaryotic organisms that were taken inside a primordial eukaryotic cell

24
Q

pinocytosis and receptor mediated endocytosis

A

endocytosis of solved proteins and molecules and receptor mediated uptake of membranes.
Simple:the ingestion of liquid into a cell by the budding of small vesicles from the cell membrane.

25
Q

autophagosome

A

organelles have a limited life span (liver mitochondrion- 10 days) autophagy recycles the organelle.

26
Q

more detail autophagy

A

Autophagy is a normal physiological process in the body that deals with destruction of cells in the body. It maintains homeostasis or normal functioning by protein degradation and turnover of the destroyed cell organelles for new cell formation. During cellular stress the process of Autophagy is upscaled and increased

27
Q

under starvation the cell

A

recycles cytosol by autophagy

28
Q

pinocytosis is also known as

A

endocytosis–> much smaller molecules than pathogens

29
Q

autophagy example

A

eating of own organelles. If a cell is starving before it dies it will eat its own mitochondria vesicles fuse around the organelle . Ultra phagosome will fuse with lysosome and it will be degraded. Organelles have a limited life span e.g. mitochondria have a 10 day life span. Under starvation the cell recycles cytosol by autophagy

30
Q

what fuses with the lysosome in autophagy

A

ultraphagosome

31
Q

mitochondrial life span in a liver cell

A

10 days

32
Q

under starvation the cell recycles cytosol by

A

autophagy

33
Q

transport vesicles

A

can move molecules between locations inside the cell, e.g., proteins from the rough endoplasmic reticulum to the Golgi apparatus. Membrane-bound and secreted proteins are made on ribosomes found in the rough endoplasmic reticulum.

34
Q

minimum size of a transport vesicle

A

25-30nm –> minimum size due tot eh bending of the membrane preventing it from being smaller

35
Q

example of a transport vesicle

A

synaptic vesicles

36
Q

how many types of proteins in transport vesicle

A

50 types

37
Q

how many types of phospholipids in a transport vesicle

A

7000

38
Q

how many cholesterol molecules in a transport vesicle

A

5700

39
Q

most prominent proteins found in vesicles are

A

vSNARES

40
Q

SNARES

A

The primary role of SNARE proteins is to mediate vesicle fusion, that is, the fusion of vesicles with their target membrane bound compartments (such as a lysosome). The best studied SNAREs are those that mediate docking of synaptic vesicles with the presynaptic membrane in neurons.

41
Q

fusion of vesicle with a target membrane (3)

A

1) tethering
2) docking–> involves interaction between tSNARES and vSNARES, this process docks it to the membrane and provides force to bend the membrane
3) fusion- tSNARE bound to vSNARE –> liana is now exposed to inner area of the endosome –> pH drops and this releases the ligand from the receptor

42
Q

what provides membrane specificity

A

SNARE receptors

43
Q

vSNAREs ligan will be complementary to

A

tSNARE receptor

e.g. an endocytic transport vesicle vSNARE will be complementary with early endosome target membrane but not the golgi apparatus target membrane 2

44
Q

vesicles can be

A

coated

45
Q

what role does the coat play

A

concentrates specific proteins in patches and moulds the forming vesicle

46
Q

coats are specific

A

for a particular place in the endocytic and exocytic pathway

47
Q

which protein coats the ER vesicle

A

COPII

48
Q

what protein coats the cis end of the golgi

A

COPI

49
Q

what protein coats the tans end of the golgi and all the early endosome

A

clathrin

50
Q

formation of a clathrin-coated vesicle in transport vesicles

A
  • specification is provided by the adaptor-receptor interaction
  • coat formation curves the membrane and shapes the vesicle
  • the coat gets rapidly least and the vesicles interact with the cytoskeleton for intracellular transport
51
Q

clathrin coat

A

triskelion (3 arms)- 6 proteins, three are clathrin heavy chains, 3 are clathrin light chains. A coat is formed when many trickskelion assemble together- due to proteins recognising each other- no proteins are needed

52
Q

no proteins ar needed to form

A

clathrin coat due to proteins recognising each other

53
Q

when is the cathrin coat removed

A

when he vesicle becomes active, the clathrin coat is recycled for the next vesicle

Molecular cell (21 decks)

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