Biology 107 (Dr. Harrington) Problem set 3

Biology 107 B2 - Problem set 3

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

a) an animal cell's gap junctions and a plant cell's plasmodesmata?

b) collagen and cellulose?

c) a Gram positive bacterial cell wall and a Gram negative bacterial cell wall?

d) the toxic LPS molecule and the Shiga toxin?

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

A. more ... more
B. more ... less
C. less ... more
D. less ... less

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).

Question 4 (organization) Draw labelled diagrams showing the structures found outside the plasma membrane of a Gram positive bactererium, a Gram negative bacterium, an Archaea cell, a yeast cell, a dandelion cell, and a human cell.