Friday, January 9, 2009

Su-more TQTQ Answers

Anna asked the following three questions -
One of the chapter quizzes (11) had the following Question:
Lipid soluble signal molecules, such as testosterone, cross the plasma membranes of all cells but affect only their target cells because?
The answer:
Intracellular receptors are present only in target cells.
Could you please explain this?
Typically, lipid signal molecules such as testosterone will bind to a receptor molecule within the cytoplasm. This molecule, now activated will then turn on gene(s).

In chapter 10 there is the talk about photosystems I and II. Can a thylakoid membrane function without one of these? Well, the thylakoid membrane is where the proteins of photosystem I and II are embedded. So the membrane can be seen as scaffolding for the photosystems. They are both part of the photosynthetic structure called a chloroplast.

What exactly is Pyruvate? Recall that cellular respiration is composed of three main steps; glycolysis, Kreb's cycle, and electron transport chain. Glucose, the food molecule, is first processed in series of reactions called glycolysis which occurs in the cytoplasm. During this process glucose is transformed into two, three-carbon molecules called pyruvate. It is pyruvate with the help of a transport protein that enters the mitochondrion for further processing. The goal of glycolysis, Kreb's cycle, and electron transport chain is to harvest the energy and transfer it to form ATP. It is ATP that can be used for work in the cell.

From Keely, this is interesting -
Since genetic disorders come from mutation in chromosomes in gametes why doesn't the body find a way to destroy mutated gametes? Like how the body destroys mutated cells during mitosis. Answer - It does seem that just as defective cells are destroyed but the immune system the same should hold true for gametes. So why not? Until release, gametes are protected by cells that in effect guard them. The cells keep away the macrophages that may destroy them.

That's all for now. I see a couple of interesting questions from Ca. I will get to those tomorrow.

Mr. Baker

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