Cell Membrane 2

Question 1

What is the difference between eukaryotes and prokaryotes in terms of energy?

Answer 1

prokaryotes utilize the proton motive force while in eukaryotic cells, energy comes from mitochondria and chloroplasts

Question 2

What is group translocation?

Answer 2

a group of proteins work together to chemically modify an incoming molecule, as a result the sugar is always traveling down its concentration gradient

Question 3

In a sugar phosphotransferase system, which is worse, a mutation in enzyme 1 or enzyme 2? why?

Answer 3

a mutation in enzyme 1, as it would remove all sugar options, while a mutation in enzyme 2 would only remove one sugar option.

Question 4

What do siderophores do?

Answer 4

essentially steal iron off of eukaryotic cells and then return to bacterial cells

Question 5

WHat are ferrichromes and enterobactin?

Answer 5

iron scavenging proteins

Question 6

What are the two pathways for protein export?

Answer 6

SEC pathway or TAT pathway

Question 7

What is the sec pathway mediated by?

Answer 7

the sec pathway is an ATP mediated system

Question 8

What are the signal peptides in the sec pathway composed of?

Answer 8

about 15-20 amino acids long, generally contain few positively charged amino acids, have a hydrophobic core, and polar grouping of amino acids

Question 9

where are the signal peptides for the sec pathway found?

Answer 9

in the N-terminus (amino terminal), and they come out first

Question 10

What is the transporter protein in the sec pathway?

Answer 10

secYEG

Question 11

What two proteins does the sec pathway use for signal recognition?

Answer 11

SecA, and SRP (signal recognition particles)

Question 12

What two proteins mediate trafficking through secYEG?

Answer 12

secA and SRP

Question 13

what is the tat pathway mediated by?

Answer 13

the proton motive force

Question 14

what does tat stand for?

Answer 14

twin arginine translocase

Question 15

What are the signal proteins found in the tat pathway?

Answer 15

two twin arginine residues at the N-terminus

Question 16

What recognizes the signals in the tat pathway?

Answer 16

tatBC

Question 17

What happens when a signal peptide binds to tatBC?

Answer 17

tatA oligomerizes into a pore

Question 18

What are the main differences between the sec and tat pathways?

Answer 18

main difference: the tat pathway does not have a transporter waiting, it requires the recognition of a signal peptide to form.
other differences: sec uses secA and SRP as signal proteins while tat uses twin arginine residues, sec is mediated by ATP while tat is mediated by proton motive force, sec transports unfolded proteins while tat transports folded proteins

Question 19

What are the 4 attributes of the sec pathway?

Answer 19

transports unfolded proteins, requires signal peptides within secreted proteins, uses two proteins for signal recognition, mediated by ATP

Question 20

What are the 4 attributes of the tat pathway?

Answer 20

transports folded proteins, requires signal proteins, transporter requires signal recognition in tatBC, mediated by proton motive force

Question 21

What are the four general steps of group translocation?

Answer 21

phosphoenol pyruvate transfers a phosphate molecule to enzyme 1, which then gets transferred to HPr, then gets transferred to enzyme 2 which differs depending on which sugar, then the phosphate is added to a sugar in enzyme 2C as it comes into the cell.