Biology 107 (Dr. Harrington) Problem set 3 answers

Biology 107 B2 - Answers to Problem set 3

Question 1 (exam) What are the similarities and differences between:

d) the toxic LPS molecule and the Shiga toxin?

One difference is that LPS is an endotoxin while the Shiga protein is an exotoxin. Endotoxins are components of bacterial cells that are only released when the cell dies and is broken up. Exotoxins on the other hand are actively exported from living cells to benefit their reproduction at the expense of their host.

I'll critique your answers for the other questions but they won't be posted.

Question 2 (exam) a Gram positive bacteria cell has _____ membrane lipids and _____ peptidoglycan than a Gram negative bacteria cell of the same size.

C. less ... more

Question 3 (thinking) Muscle cells aren't the only cells to use calcium ions as a signal. A sudden rise in cytosolic Ca⁺⁺ is the signal for neurons to release neurotransmitter molecules by exocytosis. Instead of storing Ca⁺⁺ in their SER they allow some ions to enter from outside. On this diagram showing how the calcium enters the cell, how exocytosis occurs, and how the cell restores calcium levels to normal afterwards (hint - it makes use of the Na⁺ gradient).