LECTURE 13 OBJECTIVES

Question 1

protein synthesis by free ribosomes and membrane bound ribosomes

Free ribosomes in the cytosol are:

Answer 1

soluble

Question 2

protein synthesis by free ribosomes and membrane bound ribosomes

Where are FREE PROTEIN in the cytosol exported to?

Answer 2

Cytosol, Nucleus, Mitochondria, Chloroplasts, Peroxisomes

Question 3

Where are membrane-bound ribosomes located?

Answer 3

The rough ER

Question 4

Where are the PROTEIN in the RER Lumen exported to?

Answer 4

Golgi, and then from there they travel to endosomes, and then lysosomes.

OR

Golgi, and then they are either exported into the plasma membrane or as extracellular proteins (secretory vesicles).

requires vesicualr transport

Question 5

Where does translocation move proteins to?

Answer 5

lumen or memrbane of organelle

transport across membrane

Question 6

Where does gated transport import into?

Answer 6

the nucleus

Question 7

What do membrane-bound ribosomes do?

RER

Answer 7

They initiate protein sythenis in cytsol and complete it in RER

AKA: co-translational import

Question 8

What is a SRP

singal recognition particle

Answer 8

It recognizes N-term ER signal sequence

Question 9

Protein destination:

Answer 9

transmemrbane transport + vesicular transport

Question 10

What do signal sequences do?

Answer 10

direct proteins to correct compartments

Question 11

Singal sequences importing into the RER are rich in:

Answer 11

hydrophobic amino acids

Question 12

Singal sequences importing into the nucleus are rich in:

Answer 12

postiivlty charged amino acids

Question 13

What is the nuclear envelope?

Answer 13

A double membrane bound organelle

Question 14

Nuclear envelope

Outer membrane:

Answer 14

continous with ER

Question 15

Nuclear envelope

Inner memrbane:

Answer 15

Associated with nuclear lamina (made of lamins IF)

Question 16

What is the Nuclear pore complex?

Answer 16

Protein channels in.out transport using nucleoporins

Question 17

NPC

Simple diffusion transports:

Answer 17

small hydrophillic molecules

Question 18

NPC

Gated Transport , transports:

Answer 18

Large macromolecules

(RNA, folded proteins)

Question 19

NPC - GATED TRANSPORT

Cytosol → nucleus , uses what signal?

Answer 19

nuclear localization signal

Question 20

NPC - GATED TRANSPORT

What is the transport receptor used in Cytosol → nucleus?

Answer 20

IMPORTIN

Question 21

NPC - GATED TRANSPORT

Nucleus → cytosol, signal used?

Answer 21

Nucleaor export signal

Question 22

NPC - GATED TRANSPORT

What is the transport receptor used in Nucleus → cytosol ?

Answer 22

EXPORTIN

Question 23

Ran-GEF in nucleus promotes what exchange?

Answer 23

GDP → GTP

Question 24

Ran-GAP in the cytoplasm promotes what hydrolysis?

Answer 24

GTP → GDP

Question 25

Protein nuclear transport into the cytosol requires the energy released from:

Answer 25

GTP hydrolysis mediated by Ran GAP/GEF gradien

Question 26

Process of Gated Transport via Nuclear Import (IMPORTIN)

Answer 26

1. **Recognition by importin** – NLS on cargo protein recognized by importin 2. **Transport** – translocation through NPC 3. **Release of cargo** – Binding to Ran-GTP in nucleus releases cargo 4. **Recycling of importin** – importin-Ran-GTP transported into cytoplasm where Ran- GAP hydrolyzes GTP → GDP releasing importin

Question 27

Process of Gated Transport via Nuclear Export (EXPORTIN)

Answer 27

**1. Recognition by exportin** – NES on cargo protein recognized by exportin- Ran-GTP 2. **Transport** – export complex transported into cytoplasm through NPC 3. **Release of cargo** – Ran- GAP hydrolyzes GTP → GDP releasing exportin and cargo 4. **Recycling of exportin** – exportin is diffuses back into the nucleus

Question 28

What happens in vesicular transport?

Answer 28

transport vesicles bud off from one compartment and fuse with another

Question 29

Briefly summarize the process of vesicular transport.

Answer 29

Budding happens from the lumen within the cytosol carrying cargo molecules. Then, the budded vesicles are fused with the target compartment releasing the cargo into it.

Question 30

What secretory pathway leads to exocytosis?

Answer 30

ER → Golgi → Plasma membrane

Question 31

What secratory pathway ends in the Lysosomes?

Answer 31

ER → Golgi → Endosomes

Question 32

Endocytic pathway

Answer 32

Plasma Membrane (endocytosis) → Endosomes → Lysosomes

Question 33

# Protein Import into Mitochondria What is the cytosolic receptor in matrix protein import?

Answer 33

TOM import receptor

Question 34

# Protein Import into Mitochondria What is the transport channel in matrix protein import?

Answer 34

TOM/TIM

Question 35

# Protein Import into Mitochondria What does the TOM complex do?

Answer 35

translocase of outer mitochondrial memrbane

Question 36

# Protein Import into Mitochondria What does the TIM23 complex do?

Answer 36

Translocase of the inner mitochondrial membrane

Question 37

# Protein Import into Chloroplasts What is the cytosolic receptor in stromal protien import?

Answer 37

TOC IMPORT

Question 38

# Protein Import into Chloroplasts What is the transport channel in stromal protein import?

Answer 38

TOC/TIC

Question 39

# Protein Import into Chloroplasts What does the toc complex do?

Answer 39

translocase of the outer cholorplasts membrane

Question 40

# Protein Import into Chloroplasts What does the TIC complex do?

Answer 40

Translocase of the inner choloroplast memrbane

Question 41

What is the role of coat proteins?

Answer 41

Faciliate cargo selection and the budding of vesicles

Question 42

What are the three types of coat proteins?

Answer 42

Clarthin, COPI, COPII

Question 43

What are the two Clathrin pathways?

Answer 43

AP1 (adaptin): Golgi → Lysosomes AP2: Plasma membrane → Endosomes

Question 44

What is the pathway of COPI?

Answer 44

Golgi → ER

Question 45

What is the pathway of COPII?

Answer 45

ER → Golgi

Question 46

Briefly explain the mechanisms of vesicle budding.

Answer 46

1. Recruitment - coat-recruitment GTPASE 2. Vesicle Budding 3. Vesicle scission/fission 3. Small G protein GTP hydrolysis

Question 47

What does v-SNARE (vesicle membrane) bind to? | *(FUSION)*

Answer 47

t-SNARE | *(target membrane)*

Question 48

What is tetheirng/docking?

Answer 48

Rab-GTP binds to effort protein on target memrbane