M+C lecture 2

Question 1

what is the job of the rough ER?

Answer 1

folding and assembly of its own proteins and proteins destined for other locations

Question 2

where does protein translocation occur?

Answer 2

via the translocon pore

Question 3

what is the job of the N terminal signal peptide and how is it removed?

Answer 3

connect ribosomes to available ER protein channels, it is removed by signal peptidase

Question 4

what is the signal sequence made of out?

Answer 4

small hydrophobic amino acids

Question 5

what processes do proteins undergo to enhance stability before secretion?

Answer 5

glycolysation and disulphide bond formation

Question 6

what are protein bodies?

Answer 6

proteins stored for growth and development

Question 7

where are protein bodies in plants?

Answer 7

vacuoles

Question 8

what is ricin and how is it toxic?

Answer 8

poisonous protein body in castor beans which inhibits protein synthesis

Question 9

what is a clever feature of ricin?

Answer 9

it is not catalytically active until cleaved so it avoids poisoning its own ribosomes it is also rapidly degraded once the seed germinates

Question 10

what happens to mutant/incorrectly folded proteins?

Answer 10

they are retained in the ER and targeted for degradation by lysosomes or proteasomes

Question 11

what causes the symptoms of cystic fibrosis?

Answer 11

problems with the CFTR regulator means chloride ions aren’t removed efficiently from the lumen causing a build up of mucus

Question 12

what is autophagy and where does it occur in plant cells?

Answer 12

lysis and recycling of mis folded proteins in the vacuole

Question 13

how much volume of a leaf cell does the vacuole take up in epidermal and mesophyll cells?

Answer 13

99% in epidermal and 70% in mesophyll

Question 14

what are 4 uses of vacuoles?

Answer 14

1) storage of carbohydrates and seed storage proteins
2) isolation of toxic substances
3) anti herbivory substance to stop them being eaten
4) cell turgor