Cell Membrane 2 Flashcards
What is the difference between eukaryotes and prokaryotes in terms of energy?
prokaryotes utilize the proton motive force while in eukaryotic cells, energy comes from mitochondria and chloroplasts
What is group translocation?
a group of proteins work together to chemically modify an incoming molecule, as a result the sugar is always traveling down its concentration gradient
In a sugar phosphotransferase system, which is worse, a mutation in enzyme 1 or enzyme 2? why?
a mutation in enzyme 1, as it would remove all sugar options, while a mutation in enzyme 2 would only remove one sugar option.
What do siderophores do?
essentially steal iron off of eukaryotic cells and then return to bacterial cells
WHat are ferrichromes and enterobactin?
iron scavenging proteins
What are the two pathways for protein export?
SEC pathway or TAT pathway
What is the sec pathway mediated by?
the sec pathway is an ATP mediated system
What are the signal peptides in the sec pathway composed of?
about 15-20 amino acids long, generally contain few positively charged amino acids, have a hydrophobic core, and polar grouping of amino acids
where are the signal peptides for the sec pathway found?
in the N-terminus (amino terminal), and they come out first
What is the transporter protein in the sec pathway?
secYEG
What two proteins does the sec pathway use for signal recognition?
SecA, and SRP (signal recognition particles)
What two proteins mediate trafficking through secYEG?
secA and SRP
what is the tat pathway mediated by?
the proton motive force
what does tat stand for?
twin arginine translocase
What are the signal proteins found in the tat pathway?
two twin arginine residues at the N-terminus
What recognizes the signals in the tat pathway?
tatBC
What happens when a signal peptide binds to tatBC?
tatA oligomerizes into a pore
What are the main differences between the sec and tat pathways?
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
What are the 4 attributes of the sec pathway?
transports unfolded proteins, requires signal peptides within secreted proteins, uses two proteins for signal recognition, mediated by ATP
What are the 4 attributes of the tat pathway?
transports folded proteins, requires signal proteins, transporter requires signal recognition in tatBC, mediated by proton motive force
What are the four general steps of group translocation?
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.
