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MCB1 Block 3 > Endocytosis > Flashcards

Flashcards in Endocytosis Deck (52):
1

What is covering the macrophage surface?

Receptors

2

What are the 3 different types of endocytosis?

1. Pinocytosis
2. Phagocytosis
3. receptor-mediated endocytosis

3

Pinocytosis spontaneously makes _____

vesicles

4

Receptor-mediated endocytosis have a protein ____ on membrane whose purpose is to what?

coat, to deform the membrane

5

What does receptor-mediated endocytosis create in order to engulf vesicle?

A protein coat to engulf vesicle

6

Which 2 endocytosis mechanisms are specific?

Phagocytosis & receptor-mediated endocytosis

7

Which endocytosis mechanisms need receptors?

Phagocytosis & receptor-mediated endocytosis

8

What changes in the cell during phagocytosis?

reorganization of the cytoskeleton

9

What are the 2 functions of endocytosis?

Bring material into cell
Recycle PM

10

All cells use what form of endocytosis?

pinocytosis

11

Pinocytosis is useful for bulk ___ ____

nutrient uptake

12

During pinocytosis there is no cop protein or reorganization of PM, but what is still needed when vesicle enters cell to guide it in?

motor protein walking on microtubule

13

What does phagocytosis consume?

large cells like bacteria and dying cells

14

Phagocytosis is ____ triggered but ____ independent

receptor, clathrin

15

What happens to the macrophage membrane when it engulfs another cell?

The membrane changes shape (reorganization of cytoskeleton) and starts to form around the cell it is engulfing

16

What is the first step in phagocytosis?

phagosyte binds to opsonins

17

What does the phagosome bind to when phagocytosis starts?

opsonins

18

When receptors on macrophage bind to bacteria, what happens to the membrane?

there is reorganization of the cytoskeleton - actin filaments grow and the membrane spreads around the bacteria until it fuses around the bacteria.

19

When does a macrophage become a phagosome?

after it engulfs a bacteria

20

When does a phagosome become a lysosome?

When the pH drops enough or when it fuses with a lysosome

21

How does the pH lower in a phagosome?

H-pump are constantly pumping out H and it is lowering the pH

22

What is a primary lysosome?

brand new lysosome, hasn't fused with anything yet

23

What is a secondary lysosome?

a lysosome that is or has already digested things

24

A phagolysosome will become what?

lysosome

25

What might happen to a phagosome as its degraded?

It could end up with residual body as lipfuscin

26

How does receptor-mediated endocytosis engulf?

They all bind to LDL. When receptors bind to LDL it triggers binding of COP proteins which deforms the membrane. No changes in actin, COP protein deforms the membrane.

27

Where do receptors for receptor-mediated cluster?

lipid rafts

28

In receptor-mediated endocytosis the cargo _____ binds to the cargo _____

protein, receptor

29

After the receptor binds to the protein in receptor-mediated endocytosis what protein binds next?

adaptin

30

What does adaptin bind to?

clathrin

31

What is the purpose of clathrin?

it binds to adaptin and causes deformation in membrane

32

As soon as the vesicle buds in receptor-mediated endocytosis what happens to the coat?

the clathrin coat disassembles

33

Rab-GTPase initiates what?

docking of protein to target membrane, allows v-snare to interact with t-snare

34

What's the purpose of NSF/SNAP complex?

disassembles v-snare and t-snare so v-snare can be recycled

35

What is the purpose of coating the membrane in clathrin?

to deform it and allow vesicle to enter cell

36

What is the function of adaptins?

they control coated vesicle formation in receptor-mediated endocytosis

37

Adaptins interact directly with ______ sorting signals

cytoplasmic

38

What is the structure of clathrin?

triskelion

39

What is a triskelion?

3 polypeptide chains form 3-legged structure

40

how many triskelions form a lattice around the vesicle?

36

41

What part of clathrin binds adaptin?

inner layer

42

Once the cop protein disassembles on vesicle, what is going to interact?

Rab and v-snare and t-snares will interact

43

What will an endosome become?

lysosome

44

Vesicles form at trans golgi with M6P tag, what will bind around this receptor and bring it to lysosome

adaptin

45

the longer an endosome exists, what happens to its pH?

it lowers

46

Cholesterol is transported in blood as what?

LDL (cholesteryl esters)

47

What is needed for membrane synthesis?

cholesterol

48

When a vesicle fuses with endosome, what happens to LDL?

LDL disassociates from LDL-R

49

As the pH lowers and endosome becomes lysosome, what happens to LDL?

LDL is hydrolysed to free cholesterol, can now e used to make new membranes

50

What is caveolin?

another type of protein coat that can form, but it's not well understood

51

Where do caveolae form?

lipid rafts

52

Contrast clathrin vs. caveolae

caveolae have spoked-coat morphology