15.1 - Intracell. Compartments & Prot. Trans.

Question 1

What is protein sorting?

Answer 1

The process by which proteins are directed to specific cellular locations.

Question 2

What determines the destination of a protein?

Answer 2

A sorting signal, an amino acid sequence in the protein.

Question 3

How do proteins destined for the nucleus reach their destination?

Answer 3

They pass through nuclear pores.

Question 4

What are the two types of ER?

Answer 4

Rough ER and Smooth ER.

Question 5

What is the function of the Signal Recognition Particle (SRP)?

Answer 5

It binds to the signal sequence, slows protein synthesis, and directs the ribosome to the SRP receptor on the ER

Question 6

What are the two types of proteins in the ER?

Answer 6

Soluble proteins and membrane proteins

Question 7

What is glycosylation?

Answer 7

The process of attaching oligosaccharides to proteins, converting them into glycoproteins

Question 8

What are the functions of glycosylation?

Answer 8

Protect proteins from degradation, guide proteins to organelles, and promote cell recognition

Question 9

What happens to misfolded proteins in the ER?

Answer 9

They are either folded correctly by chaperones or degraded if folding fails

Question 10

What is the cis face of the Golgi apparatus?

Answer 10

The entry side of the Golgi where proteins arrive from the ER.

Question 11

What are the two types of protein secretion?

Answer 11

Unregulated secretion and regulated secretion.

Question 12

What is an example of regulated secretion?

Answer 12

Insulin release based on blood glucose levels.

Question 13

Cells undergo translation to produce _____

Answer 13

polypeptides

Question 14

What happens to polypeptides after translation?

Answer 14

They are modified and transported within the cell to perform their functions

Question 15

What determines where a protein is sent in the cell?

Answer 15

A sorting signal (amino acid sequence) directs the protein to the correct location

Question 16

What are the destinations of proteins within a cell?

Answer 16

Nucleus (via nuclear pores).
Chloroplasts, mitochondria, peroxisomes, and ER (via translocators).
Other destinations (via vesicles from the ER).

Question 17

How does the sorting signal guide proteins?

Answer 17

It is a specific amino acid sequence that directs proteins to their appropriate locations.

Question 18

What are the structural differences between rough and smooth ER?

Answer 18

Rough ER has ribosomes attached to its surface, while smooth ER does not.

Question 19

What happens to proteins with an ER signal sequence?

Answer 19

Ribosomes synthesizing these proteins bind to the ER, and the proteins enter the ER via translocation channels

Question 20

What is the role of the Signal Recognition Particle (SRP)?

Answer 20

It binds to the signal sequence, slows protein synthesis, and guides the ribosome to the SRP receptor on the ER.

Question 21

What happens to soluble proteins in the ER?

Answer 21

They are released into the lumen of the ER, modified, and transported to their destinations

Question 22

What happens to membrane proteins in the ER?

Answer 22

They remain embedded in the ER membrane and are anchored by stop-transfer sequences

Question 23

What is glycosylation?

Answer 23

The addition of oligosaccharides to proteins, converting them into glycoproteins

Question 24

What is the function of oligosaccharides in glycosylation?

Answer 24

1. Protect proteins from degradation.
2. Guide proteins to other organelles.
3. Promote cell recognition

Question 25

What role do chaperone proteins play in the ER?

Answer 25

They ensure proper folding of proteins and direct misfolded proteins for degradation if necessary

Question 26

How do proteins leave the ER?

Answer 26

They bud off in vesicles and fuse with the Golgi apparatus.

Question 27

What are the entry and exit points of the Golgi?

Answer 27

Entry: Cis face Exit: Trans face

Question 28

What modifications occur in the Golgi?

Answer 28

Proteins undergo further oligosaccharide processing and are sorted to lysosomes, the cell surface, or back to the ER

Question 29

What is unregulated secretion?

Answer 29

Continuous delivery of membrane proteins (e.g., receptors) to the cell surface

Question 30

What is regulated secretion?

Answer 30

Controlled release of proteins, such as insulin, in response to specific signals like blood glucose levels

Question 31

How are ribosomes directed to the ER during protein synthesis?

Answer 31

Ribosomes synthesizing proteins with an ER signal sequence bind to the ER membrane, directing these proteins into the ER via translocation channels.

Question 32

What mechanism explains how proteins destined for the ER enter the organelle?

Answer 32

The ER signal sequence and translocation channels guide proteins into the ER as they are synthesized.

Question 33

What mechanism shows how proteins are guided to their destinations within a cell?

Answer 33

Signal sequences act as "addresses," guiding proteins to their correct locations in the cell based on their specific amino acid sequence

Question 34

What mechanism involves the Signal Recognition Particle (SRP) in guiding ribosomes to the ER?

Answer 34

SRP binds to the ER signal sequence, slows protein synthesis, and directs the ribosome to the SRP receptor on the ER membrane

Question 35

How does the SRP system ensure accurate targeting of proteins to the ER?

Answer 35

By binding to the signal sequence, SRP pauses synthesis and interacts with the SRP receptor to ensure the ribosome attaches to the ER correctly

Question 36

What mechanism explains how soluble proteins are released into the ER lumen?

Answer 36

Soluble proteins are guided into the ER lumen during synthesis and are released into the lumen to undergo modification and transport

Question 37

How do membrane proteins anchor themselves within the ER membrane?

Answer 37

Stop-transfer sequences within membrane proteins interact with the ER membrane, halting translocation and embedding the protein into the membrane.

Question 38

What mechanism describes how proteins are glycosylated in the ER?

Answer 38

Oligosaccharides are transferred from the lipid Dolichol to asparagine residues on proteins, converting them into glycoproteins. This process protects proteins, guides them to organelles, or aids in cell recognition.

Question 39

What mechanism involves chaperone proteins in ensuring proper protein folding?

Answer 39

Chaperones fold proteins properly in the ER, and if folding fails, they direct misfolded proteins for degradation. Properly folded proteins are packaged into vesicles for transport to the Golgi apparatus.

Question 40

What mechanism sorts and transports proteins through the Golgi apparatus?

Answer 40

Proteins enter the Golgi at the cis face, undergo further oligosaccharide modifications, and are sorted at the trans face for lysosomes, the cell surface, or recycling back to the ER.

Question 41

How does the Golgi apparatus handle proteins after modification?

Answer 41

The trans-Golgi network directs proteins to their destinations, such as the plasma membrane, lysosomes, or secretory vesicles.

Question 42

What mechanism explains how proteins are secreted from the cell?

Answer 42

Secretory vesicles transport proteins from the Golgi apparatus to the plasma membrane, where they are released via unregulated or regulated secretion.

Question 43

How does regulated secretion work?

Answer 43

Proteins, such as insulin, are stored in secretory vesicles and released only in response to specific signals, like changes in blood glucose levels.