Secretory Pathway

Question 1

Describe Step 1 of the Secretory Pathway

Answer 1

Free ribosome initiates protein synthesis

Question 2

Describe Step 2 of the Secretory Pathway

Answer 2

Hydrophobic N-terminal signal sequence produced

Question 3

Describe Step 3 of the Secretory Pathway

Answer 3

Signal sequence of protein is recognised and bound to by Signal Recognition Particle (SRP)

Question 4

Describe Step 4 of the Secretory Pathway

Answer 4

Protein synthesis briefly stops

Question 5

Describe Step 5 of the Secretory Pathway

Answer 5

GTP-bound SRP directs the ribosome to SRP receptors on cytosolic face of endoplasmic reticulum

Question 6

Describe Step 6 of the Secretory Pathway

Answer 6

SRP disassociates

Question 7

Describe Step 7 of the Secretory Pathway

Answer 7

Protein synthesis continues and newly formed protein fed into ER via peptide translocation complex

Question 8

Describe Step 8 of the Secretory Pathway

Answer 8

Signal sequence removed by signal peptidase once entire protein has been synthesised

Question 9

Describe Step 9 of the Secretory Pathway

Answer 9

Ribosome disassociates and is recycled

Question 10

How are ER membrane proteins retained?

Answer 10

Stop Transfer sequence (multiple sequences if multiple domains) specifically aims to make sure not all protein enters the ER.