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Reading:
Rieke, F., and D. A. Baylor, 1998, "Single-photon detection by rod cells of the retina," Reviews of Modern Physics, 70(3), 1027-1036. Download [PDF] [From Publisher Site (UW restricted)]

And one of the following:
Aidley Chapter 10 p 173-190
or KSJ (4th edition) Chapter 14 p 253-270
or KSJ (3rd edition) Chapter 13

1. Read the paper by Rieke & Baylor ("Single-photon detection by rod cells of the retina" handed out in class). I don't expect you to understand all the details of the paper, just the big picture. The last paragraph of the paper (page 1035, section VII) lists 3 fundamental unanswered questions. Choose ONE of the 3 questions and then in TWO PAGES OR LESS do the following: (1) Explain the motivation for the question (i.e. why the answer is important to understanding how we see). (2) Briefly summarize what is known about the question and/or the possible hypotheses.

2. When a baby is born, its retina is still developing. Their rods are just like the rods of adults, except that they are much shorter--baby's rods have only a dozen or so disks in their outer segments compared to several hundred in an adult's rods. Many parameters are the same for adult rods and baby rods, including: concentration of all proteins in the disk (rhodopsin, transducin, phosphodiesterase), properties of the inner segment, the density of channels in the outer segment, the concentration of cGMP, etc.

Below is a list of parameters we've talked about in class. Ignore the effects of calcium for this problem. For each of the parameters, do the following: (1) explain whether you'd expect it to be the same or different in baby rods compared to adult rods. (2) explain why it is the same or different. (3) if different, explain qualitatively (i.e. say bigger/smaller, faster/slower, etc) how the baby rod would be different & why.

A: Probability of absorbing a photon of a given wavelength
B: # of thermal activations of rhodopsin/unit time/rod
C: Relative absorbance spectrum of the rod
D: Magnitude of the current flowing into the outer segment in the dark
E: Magnitude of the current flowing into the outer segment in bright light
F: # of transducin molecules activated by a single active rhodopsin
G: Fraction of cGMP molecules in the rod outer segment destroyed as the result of a single active rhodopsin