Endocytosis

Question 1

What is covering the macrophage surface?

Answer 1

Receptors

Question 2

What are the 3 different types of endocytosis?

Answer 2

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

Question 3

Pinocytosis spontaneously makes _____

Answer 3

vesicles

Question 4

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

Answer 4

coat, to deform the membrane

Question 5

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

Answer 5

A protein coat to engulf vesicle

Question 6

Which 2 endocytosis mechanisms are specific?

Answer 6

Phagocytosis & receptor-mediated endocytosis

Question 7

Which endocytosis mechanisms need receptors?

Answer 7

Phagocytosis & receptor-mediated endocytosis

Question 8

What changes in the cell during phagocytosis?

Answer 8

reorganization of the cytoskeleton

Question 9

What are the 2 functions of endocytosis?

Answer 9

Bring material into cell

Recycle PM

Question 10

All cells use what form of endocytosis?

Answer 10

pinocytosis

Question 11

Pinocytosis is useful for bulk ___ ____

Answer 11

nutrient uptake

Question 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?

Answer 12

motor protein walking on microtubule

Question 13

What does phagocytosis consume?

Answer 13

large cells like bacteria and dying cells

Question 14

Phagocytosis is ____ triggered but ____ independent

Answer 14

receptor, clathrin

Question 15

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

Answer 15

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

Question 16

What is the first step in phagocytosis?

Answer 16

phagosyte binds to opsonins

Question 17

What does the phagosome bind to when phagocytosis starts?

Answer 17

opsonins

Question 18

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

Answer 18

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

Question 19

When does a macrophage become a phagosome?

Answer 19

after it engulfs a bacteria

Question 20

When does a phagosome become a lysosome?

Answer 20

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

Question 21

How does the pH lower in a phagosome?

Answer 21

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

Question 22

What is a primary lysosome?

Answer 22

brand new lysosome, hasn’t fused with anything yet

Question 23

What is a secondary lysosome?

Answer 23

a lysosome that is or has already digested things

Question 24

A phagolysosome will become what?

Answer 24

lysosome

Question 25

What might happen to a phagosome as its degraded?

Answer 25

It could end up with residual body as lipfuscin

Question 26

How does receptor-mediated endocytosis engulf?

Answer 26

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.

Question 27

Where do receptors for receptor-mediated cluster?

Answer 27

lipid rafts

Question 28

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

Answer 28

protein, receptor

Question 29

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

Answer 29

adaptin

Question 30

What does adaptin bind to?

Answer 30

clathrin

Question 31

What is the purpose of clathrin?

Answer 31

it binds to adaptin and causes deformation in membrane

Question 32

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

Answer 32

the clathrin coat disassembles

Question 33

Rab-GTPase initiates what?

Answer 33

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

Question 34

What's the purpose of NSF/SNAP complex?

Answer 34

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

Question 35

What is the purpose of coating the membrane in clathrin?

Answer 35

to deform it and allow vesicle to enter cell

Question 36

What is the function of adaptins?

Answer 36

they control coated vesicle formation in receptor-mediated endocytosis

Question 37

Adaptins interact directly with ______ sorting signals

Answer 37

cytoplasmic

Question 38

What is the structure of clathrin?

Answer 38

triskelion

Question 39

What is a triskelion?

Answer 39

3 polypeptide chains form 3-legged structure

Question 40

how many triskelions form a lattice around the vesicle?

Answer 40

36

Question 41

What part of clathrin binds adaptin?

Answer 41

inner layer

Question 42

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

Answer 42

Rab and v-snare and t-snares will interact

Question 43

What will an endosome become?

Answer 43

lysosome

Question 44

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

Answer 44

adaptin

Question 45

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

Answer 45

it lowers

Question 46

Cholesterol is transported in blood as what?

Answer 46

LDL (cholesteryl esters)

Question 47

What is needed for membrane synthesis?

Answer 47

cholesterol

Question 48

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

Answer 48

LDL disassociates from LDL-R

Question 49

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

Answer 49

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

Question 50

What is caveolin?

Answer 50

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

Question 51

Where do caveolae form?

Answer 51

lipid rafts

Question 52

Contrast clathrin vs. caveolae

Answer 52

caveolae have spoked-coat morphology