Ch 15

Question 1

Relationship between nucleus and ER

Answer 1

outer nucleus membrane is connected to membrane of ER

Question 2

Smooth ER function

Answer 2

steroid hormone synthesis in endocrine cells

Question 3

Golgi apparatus function

Answer 3

Receives proteins and lipids from ER, modifies them, and then dispatches (via vesicles) them to other destinations.

Question 4

Endosome function

Answer 4

sorts ingested molecules + recycles some

Question 5

lysosome function

Answer 5

degrades worn-out organelles, macromolecules and particles taken in by endocytosis
- contains hydrolytic enzymes (that can only function in acidic environments)

Question 6

peroxisomes function

Answer 6

breaks down lipids + destroy toxic molecules

Question 7

Properties of transport through nuclear pores

Answer 7

• proteins remain folded
• go through nuclear pores (selective to macromolecules, free diffusion to small micromolecules )

Question 8

Properties of Transport across Membranes

Answer 8

• proteins usually unfolded
• transport via protein translocators
  (proteins must unfold to bind to transolcators + pass through hydrophobic regions of membrane)

Question 9

Properties of transport by vessicles

Answer 9

• involved in endo / exocytosis
• move via transport vessicle
• proteins remain folded

Question 10

Signal sequences function

Answer 10

direct proteins to the correct destination
- 15 to 60 amino acids long

Question 11

Nucelus properties

Answer 11

• double membrane
• connects to ER (for export from nucleuss)
• has nuclear pores (for import into nucleus)

Question 12

Function of cystolic fibrils

Answer 12

weave in intricate formations to be selectively permeable to macromolecules

Question 13

How do nuclear proteins get into the nucleus?

Answer 13

through the help of a nuclear import receptor that binds to proteins

Question 14

What (and how does it) drives nuclear transport?

Answer 14

GTP hydrolysis

1. Ran-GTP binds to receptor inside nucleus (allows receptor to exist nucleus)
2. GTP is hydrolyzed, GDP dissociates from receptor (allows receptor to bind to proteins in the cytosol)

Question 15

How do proteins enter mitochondria?

Answer 15

1. protein binds to import receptors
2. they unfold and pass through a protein translocator in outer membrane
3. then, they pass through another protein translator in inner membrane
4. signal sequence is cleaved off once inside matrix of mitochondria (mature protein forms)

Question 16

Relationship between ribosomes and proteins

Answer 16

proteins bind to ribosomes to get synthesized.

Free ribosome cycle –> creates cytosolic proteins
membrane-bound ribosome cycle –> creates proteins that then enter the ER

Question 17

How do ribosomes bind to ER membrane

Answer 17

proteins synthesized by ribosomes meant to enter the ER have an ER signal sequence

signal recognition particle (SRP) attaches to ribosome and binds to SRP receptor on cytosolic side of ER.

Question 18

Where do stuff go in exocytosis?

Answer 18

1. From Golgi Apparatus to plasma membrane
2. From Golgi Apparatus to endosome to lysosome

Question 19

Clathrin function

Answer 19

forms coated vesicles (protects from other proteins that might digest vesicles before it gets to where it goes )

Question 20

What is glycosylation’s function?

Answer 20

• protects protein from degradtation
  (asparagine is glycosylated )
• holds it in ER until protein is folded
• helps guide it to appropraite organelle

Question 21

How does the cell deal with misfolded proteins

Answer 21

• retain in ER –> alters size of ER if there is many misfolded proteins
• unfolded protein response (UPR) –> activates chaperone proteins to refold proteins
• apoptosis (cell death) –> for a TON of misfolded proteins

Question 22

2 pathways of exocytosis

Answer 22

1. constitutive secretion (constant secretion)
2. regulated secretion (requires extracellular signal in order to secrete) ex. neurotransmitters leave presynaptic membrane in nerve conduction when voltage gates for Ca2+ open and let Ca2+ to enter cell)

Question 23

2 types of endocytosis

Answer 23

1. pinocytosis (<150mm vesicles)
2. phagcytosis (>250 mm vesicles)
   –> uses pseudopods to engulf large stuff like other cells

Question 24

How do virus enter the cell

Answer 24

• hack endocytic system (specifically by hijacking receptor-mediated endocytosis)

Question 25

3 pathways to lysosome

Answer 25

1. phagocytosis
2. endocytosis
3. autophagy via autophagosomes (automatic degredation of old organelles)