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Mfouts
#1 Posted : Thursday, July 05, 2012 1:41:12 AM
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Hey,

Just a few misc. questions:

1. As a general rule of thumb, proteins produced in the Rough ER are destined to the inner membrane system, while those produced in the cytosol on free floating ribosomes can be distributed to other parts of the cell, but this isn't always the case, right? Or, are the majority of free-floating ribosome within the vicinity of the rough er, so they just describe it as being produced from the rough er? Let me know where i'm going wrong here...

2. How effective is bacterial aerobic respiration considering they don't have a membrane organelle to control the [H+]? They would be subjected to their environmental concentrations would they not?

3. Which of the ECM has the greatest strength? I know intermediate filaments are stronger than microfilaments (actin), I assume microtubules are stronger than intermediate? I'm trying to relate the strength to desmosomes, gap junctions, and tight junctions...

4. I'm having some trouble with questions dealing with genetic crosses where they give you a description of either a recessive autosomal/sex-linked and then ask the percentage of either boy or girl. What's tricking me is when you have to take into account whether to multiply the outcome of the passage of genotype (which i can do) by the occurrence of a boy/girl. Often they mix up the amount of kids and ask either boy or girl etc. So my question is how do you know when they want you to take in account the probability of male/female children? To me, it would seem obvious in the question stem, but i've found the way they word it can be confusing.

5. Last one, i think the answer key is wrong in the back for lec. 9 critical question 3. It states the answer is C, but the description matches B. Could you clarify the correct answer?

Thanks in advance !
alfredbasilious
#2 Posted : Tuesday, July 10, 2012 12:13:45 PM
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(1) Proteins destined to be membrane bound start their synthesis at free floating ribosomes. But once the signal peptide has been transcribed, the entire ribosome complex is carried to the SRP-receptor protein on the RER. Translation of the protein continues on the RER bound ribosome and the protien being synthesized is fed into the lumen of the RER.

(2) The bacteria use the cell membrane as the ETC. Their make more ATP per Glucose molecule because they don't lose ATP potential when they transport NADH from the cytosol and into the mitochondrion.

(3) In order of decreasing strength: Desmosomes, Tight Junctions, Gap Junctions.

(4) When we are talking about sex linked traits it is important to make a distinction between male and female children since they are XY and XX respectively and the probability of expressing a specific phenotype will vary between males and females. However, when looking at autosomal traits, male/female distinctions are not necessary since they both have the same probability of expressing a given phenotype.

(5)Yes, the answer is B for this question.
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