Comprehension - L08-L09

Question 1

What 5 things are a part of the endo-membrane system?

Answer 1

ER
Golgi Complex
Endosomes
Lysosomes
Vacuoles

Question 2

What are the 3 steps of the endomembrane system?

Answer 2

1. Transport materials from donor to recipient compartment
2. Transport materials out of the cell (secretory)
3. Transport materials into the cell (endosytic)

Question 3

During the transport of materials from the donor compartment the recipient compartment, what happens to the proteins?

Answer 3

Proteins (secreted proteins, lysosomal enzymes, membrane proteins) are directed to the correct destination with sorting signals

Question 4

During the transport of materials from the donor compartment to the recipient compartment, what are the sorting signals and what do they do?

Answer 4

• Amino acid sequences
• Attached oligosaccharides
  Signals are recognized by receptors in the membranes of budding vesicles

Question 5

In the Secretory Pathway, what are the types of biomolecules synthesized in the ER?

Answer 5

• Lipids
• Steroid hormones
• Secreted proteins
• Integral membrane proteins
• Glycosolyation of proteins

Question 6

Modifications occur where?

Answer 6

The Golgi complex

Question 7

What happens in constitutive secretion?

Answer 7

• Materials are continually transported in secretory vesicles from their site of synthesis and secreted
• Contributes to the formation of the plasma membrane

Question 8

What happens in the regulated secretion?

Answer 8

Materials are stored in membrane bound compartments and only are released due to stimuli

Question 9

What happens in the endocytic pathway?

Answer 9

Materials move from the outer surface of the cell to compartments within the cell (endoscopes and lysosomes)

Question 10

In the endocytic pathway, what do endosomes do?

Answer 10

Materials are taken up and are transported to early endoscopes for sorting
Late endosomes are more acidic
Fuse with lysosomes to deliver cargo for degradation

Question 11

In the endocytic pathway, what do lysosomes do?

Answer 11

Hydrolytic (digestive) enzymes and acidic pH
Roles in breakdown of material and organelle turnover

Question 12

What is autoradiography?

Answer 12

Following the location of radioactively labeled materials in a cell
Pulse chase experiment

Question 13

What is the Pulse step of Pulse Chase?

Answer 13

Radio-labelled amino acids are incorporated in the digestive enzymes being synthesized
Exposed to the radio labelled aa for only a short time

Question 14

What is the Chase step of the Pulse Chase?

Answer 14

• Transfer cells to media with only unlabelled aa
• Enzymes synthesized during this time will not be radio labeled

Question 15

What are the characteristics of the Rough ER?

Answer 15

• Ribosomes bound on cytosolic surface
• Network of cistern
• Continuous with the outer membrane of nuclear envelope

Question 16

What are the characteristics of the Smooth ER?

Answer 16

• Lacks ribos
• Interconnected curved, tubular membranes
• Continuous with Rough ER

Question 17

What are the functions of the smooth ER?

Answer 17

• Synthesis of steroid hormones
• Synthesis of membrane lipids
• Detox of liver compounds
• Sequester Ca2+ ions in muscle

Question 18

What are some functions of the Rough ER?

Answer 18

• Protein synthesis
• Addition of sugars is initiated

Question 19

What happens in the RER ribosomes?

Answer 19

1/3 of proteins are made
Cotranslational translocation where peptides move into the lumen of the ER as it is being synthesized by the ribo

Question 20

What happens in the Free ribosomes?

Answer 20

2/3 of proteins are synthesized
proteins released into cytosol

Question 21

What is cotranslational translocation?

Answer 21

Synthesis of secreted proteins and soluble proteins that reside in endomembrane

Question 22

All protein synthesis begins on what?

Answer 22

A free ribosome

Question 23

Which end does cotranslational translocation synthesize first?

Answer 23

N-Terminal end gets synthesized first

Question 24

In cotranslational translocation, what does SRP Stand for and what does it do?

Answer 24

Signal Recognition Particle binds to the signal sequence and the ribosome
Polypeptide synthesis is halted temporarily

Question 25

The amino acids that flank the cytosolic end of the transmembrane domain are (Positive/Negative)

Answer 25

Positively charged amino acids

Question 26

What are the positively charged amino acids?

Answer 26

Arginine (R, Arg)
Lysine (K, Lys)
Histidine (H, His)

Question 27

What does PE do?
What does PS do?
What does PI do?

Answer 27

PE: Promotes curvature
PS: -ve charge interacts with transmembrane protein
PI: Roles in signal transduction

Question 28

What happens in cotranslational translocation if the positive charges are on the N terminal side of the transmembrane domain?

Answer 28

The translocon will reorient the transmembrane domain