Chap. 8 part 2

Question 1

role of the golgi body (Golgi complex)

Answer 1

Cis Golgi Network - Functions to sort proteins the ER or the next Golgi station
Medial cisternae - where processing take place
Trans Golgi Network - functions in sorting proteins either to the membrane or various intracelluar destinations

Question 2

Functions of glycosylation

Answer 2

the N-linked oligossaccharide that was added to nearly every protein in the ER is further process int he Golgi apparatus
Gives a cell the ability to generate many chemically distinct molecules at the cell surface

Question 3

basic difference between vesicular transport and the cisternal maturation model

describe each model

Answer 3

Vesicular Transport Model
- cargo is shuttled through the cis to the trans Golgi network
Cisternal Maturation Model
- the vesicular tubular cluster matures into a cistern and moves along from the cis to the trans face

There is retrograde transport of vesicles in both models

Question 4

What is the VTC and where is it located?

Answer 4

it is the Vesicular Tubular Cluster and its located in the endoplasmic reticulum-golgi intermediate compartment
- it mediates traffic between the golgi and ER

Question 5

basic structure and role of COP1

Answer 5

Protein Coated vesicles that move materials backwards (retrograde transport) from the VTC in the ERGIC to the ER

Question 6

basic structure and role of COP2

Answer 6

Protein Coated vesicles that move materials forward (antegrade transport) to the VTC in the ERGIC from the ER

Question 7

role of clathrin coated vesicles

Answer 7

to move materials from the trans golgi network to endosomes and lysosomes

Question 8

Role of a KDEL sequence

Answer 8

This is the signal on the resident ER proteins that get transported to the golgi in COP2 vesicles to get them returned by to the ER by COP1 vesicles.
- if they don’t have this sequence, they will never return back
- the sequence binds to a KDEL receptor

Question 9

How does vesicle budding begin?

Answer 9

• a recruitment of GTP binding protein to the donor membrane
• binding of the cytosolic coat protein to the domain of the membrane cargo proteins

Question 10

Role of V SNARE and example

Answer 10

they mediate membrane fusion, they become incorporated in the membrane of the vesicles during budding

example: synaptobrevin

Question 11

role of T SNARE and example

Answer 11

they mediate membrane fusion, they are in the target membrane during budding

example: syntaxin

Question 12

Role of a mannose 6-phosphate tag

Answer 12

to get the lysosomal enzymes to the trans golgi

the TAG gets added in the cis golgi

Question 13

Role of a mannose 6-phosphate receptor

Answer 13

to detect the tag and get the lysosomal enzymes from the TGN to lysosomes

Question 14

Role of lysosome

Answer 14

they contain 50 types of hydrolytic enzymes (produced in the RER) virtually hydrolyze every type of macromolecule.

Optimal pH is 4.6

Question 15

How are hydrolytic enzymes targeted?

Answer 15

They get tagged with phosphorylated mannose residues and recognized by MPRs (mannose 6-phosphate receptor)

Question 16

what is bulk phase endocytosis?

Answer 16

aka Pinocytosis
its the non specific uptake of extracellular fluids

Question 17

what is the receptor mediated endocytosis?

Answer 17

or clathrin mediated endocytosis
bring the uptake of specific ligands to their receptor on the external surface of the plasma membrane

Question 18

The formation of clatherin coated vesicles

Answer 18

the outer shell is made of clatherin and triskelion which consist of three large and three small polypeptide chains
the inner shell is made of GGA adaptor proteins which interacts with the clathrin, MPR and G proteins

Question 19

Role of GGA Adaptor proteins

Answer 19

contain multiple subunits having different functions
- they engage the cytoplasmic tails of specific receptors to select bound cargo molecules and bind and recruit the clatherin molecules of the overlying lattice

Question 20

Role of dynamin

Answer 20

its a G protein needed to release clathrin-coated vesicle from the membrane where it forms
- it pinches off the vescicles from the exoplasmic face with the help of GTP

Question 21

Basic Mechanisms of Phagocytosis

Answer 21

reuptake of large particles and is receptor mediated in mammals

Question 22

4 compartments of mitochondria for protein

Answer 22

• matrix
• inner mitochondrial membrane (IMM)
• intermembrane space
• outer mitochondrial membrane (OMM)

Question 23

Basics of mitochondrial import

Answer 23

1) the protein has to be relatively unfolded or extended
2) Has to go through TOM
3) rather go through TIM22 or TIM23

Question 24

Role of TOM complex

Answer 24

Transporter of outermsmbrane which has an receptor on its channel

Question 25

Role of TIMs complexes

Answer 25

Transporter of inner membrane

TIM22: for integral proteins of the inner mitochondrial membrane
TIM23: for protein for the matrix

Both have receptors

Question 26

Role of location of signal sequences

Answer 26

for TIM22 the signal sequence is internal and remain a part of the molecule

for TIM23 the signal sequence is at the N terminus and it’s removed

Question 27

what is the structure of the nuclear envelope

Answer 27

it has 2 membranes and the outer one is continuous with the ER

Question 28

role of nuclear pores (nuclear pore complex)

Answer 28

allows ions, small metabolites and globular proteins to go through
ex. nuclear protein synthesized in the cytoplasm, mRNA, tRNA ribosomal subunits

Question 29

Nuclear Localization Signals

Answer 29

there is a specific stretch of positively charged amnio acids that allows access into the nucleus, if there is an mutation, the protein fails to localize into the cell.
if a NLS is fused on a non protein, that will become concentrated in the nucleus

Question 30

How does a protein get imported into the nucleus?

Answer 30

1) the importin alpha/beta cargo complex docks on the cytoplasmic filament before it moves into the nucleoplasm through the nuclear pore complex

2) in the Nucleoplasm, importing Beta interacts with Ran-GTP to release the cargo

3) They both relocate into the cytoplasm and Ran-GTP is hydrolyzed into Ran-GDP

4) importin alpha is brought into the cytoplasm by exportin

5) importin Beta can now bind to importin alpha
cycle restarts

Question 31

what kind of protein Ran is

Answer 31

its a member of a class of protiens called small-GTPases

Question 32

How does Ran-GTP turn into Ran-GDP?

Answer 32

Ran-GAP and Ran-GEF help with the enzymatic hydrolysis to REPLACE the RAN-GtP with RAN-GDP

Question 33

What is RAN-GAP

Answer 33

GAP are GTPase Activating Proteins

Question 34

What is RAN GEF

Answer 34

GEF is Guanine Nucleotide Exchange Factor