Golgi

Question 1

Golgi do to glycoprotein and membrane lipid

Answer 1

Process and sort them
Glycosylation and processing of carbohydrates side chain occurs, then distributed to other locations

Question 2

What happens to proteins released into ER lumen

Answer 2

Golgi apparatus
Secretory vesicles
Lysosome
Back to ER

Question 3

CGN

Answer 3

Sorting of proteins to be sent back to ER or on the golgi

Question 4

TGN

Answer 4

Segregating proteins into vesicles headed to plasma membrane

Question 5

Terminal glycosylation

Answer 5

Occur in golgi
Modification of glycoproteins through removal/addition of sugar side chain on the core oligosaccharide (added in ER)
Happen on luminal side

Question 6

Great diversity of type of glycosylation because ———

Answer 6

Enzyme being very specific for certain carbohydrates

Question 7

Each step of glycosylation depends on

Answer 7

Presence of previous carbohydrates
That why it is critical

Question 8

Glycosylation is a ——— process

Answer 8

Linear

Question 9

Glycosylation function

Answer 9

-proteins/lipid sorting
-makes glycoproteins more resistant to digestion by proteases
-recognition molecule in cell-cell interaction
-regulatory roles

GOVE CELL ABILITY TO GENERATE MANY CHEMICALLY DIFFERENT MOLECULES

Question 10

Movement through golgi

Answer 10

1- stationary cisternae model
2- cisternal maturation model

Question 11

Stationary cisternae vs cisternal maturation

Answer 11

Stationary:
Cisternae and resident s enzymes stay in place while cargi move forward
cargo would be found in vesicles
#there would be little change in golgi structure
++ealry and late golgi proteins would never co localize
Cisternal:
Cargo remain in cisternae while cisternae move forward
resident enzyme found in vesicles
#golgi would disappear
++ cisternae would express early then late resident proteins

Question 12

Movement of material toward plasma membrane

Answer 12

Anterograde transport

Question 13

Movement of material toward ER

Answer 13

Retrograde transport

Question 14

Sorting of proteins

Answer 14

Begin in ER
Final sort in TGN

Question 15

Protein Targeting

Answer 15

—Protein synthesized on RER must be directed to variety location
—Each protein has specifc tag targeting it to transport vesicle that take ot to correct location

Question 16

Protein residency

Answer 16

Proteins are kept by two mechanisms
Retention and Retrieval

Question 17

Retention

Answer 17

Resident molecules are excluded from transport vesicles

Question 18

Retrieval

Answer 18

Tags can be used to return escaped proteins

Question 19

Tags on proteins

Answer 19

Depends on proteins and destination
Tag can be amino acid sequence, hydrophobic domain or oligosaccharide side chain

Question 20

Protein composition of ER is maintained by

Answer 20

1- preventing proteins from escaping
2- returning others from golgi

*these proteins don’t need targeting sequence since they were synthesized in ER

Question 21

retention and retrieval is done by

Answer 21

1- soluble ER specific proteins
2- ER specific transmembrane proteins

Question 22

Soluble ER specific proteins

Answer 22

Most common ER retention tag is KDEL retrieval signal that mediate the return of soluble proteins to ER

Question 23

KDEL retrieval signal

Answer 23

C-terminal amino acid sequence

Question 24

ER-specific transmembrane proteins

Answer 24

Membrane proteins have Retention signals on their cytosolic domains which binds to vesicle coat proteins, facilitate their return to ER

Question 25

ER specific transmembrane Proteins

Answer 25

KKXX

Question 26

KDEL proteins are

Answer 26

ER residents

Question 27

If KDEL proteins escape to golgi

Answer 27

1- associate with KDEL receptors (efficient binding in low ph of gogli)

2- KDEL receptor package KDEL proteins in ER-bound transport vesicle

3- KDEL receptors release proteins in the ER (binding is inefficient in high ph of ER)

Question 28

Targeting to lysosome

Answer 28

Soluble lysosomal enzymes undergo n-glycosylation followed by removal of glucose and mannose in ER and early golgi
Then phosphrylated in golgi

Forming mannose-6-phosphate tag

Question 29

Mannose-6-phosphate tag

Answer 29

Ensure delivery of lysosomal proteins to lysosome

Question 30

Mannose-6-phosphate receptor

Answer 30

Mannose-6-phosphate tag and the enzyme bind to receptor

In low ph, dissociation of enzyme and receptor

Receptor is recycled