Very good points, all. Thank you very much. Yes, I gave them credit. Chet Harbut, Ph.D. Biology Dept. Cerritos Community College 11110 E. Alondra Blvd Norwalk, CA 90650 (562) 860-2451 ext: 2684 -----Original Message----- From: HAPS-L-owner@xxxxxxxxxxx on behalf of Tom Lehman Sent: Mon 2/12/2007 12:55 PM To: HAPS-L@xxxxxxxxxxx Subject: RE: [HAPS-L] End-product inhibition Hi, I would argue, in this case, in favor of the students. They've shown that you may need to re-write your question to be more specific. You can state, in the question, that you're looking for a negative-feedback example in the control systems (which would exclude intracellular pathways). I've been caught by students on occasion who read a question differently than I but could justify their answer afterwards. It's hard to get mad at students who make me learn. Tom ________________________________ From: HAPS-L-owner@xxxxxxxxxxx [mailto:HAPS-L-owner@xxxxxxxxxxx] On Behalf Of Weck, Margaret Sent: Monday, February 12, 2007 8:59 AM To: HAPS-L@xxxxxxxxxxx Subject: RE: [HAPS-L] End-product inhibition But isn't this at a lower level of organization than the systems we usually refer to as "control systems"? I would say end-product inhibition is negative feedback, but it isn't an example of a "control system" because it is happening at the molecular rather than cellular level. What do others think? Margaret W. ________________________________ From: HAPS-L-owner@xxxxxxxxxxx [mailto:HAPS-L-owner@xxxxxxxxxxx] On Behalf Of James S. Miller Sent: Monday, February 12, 2007 9:19 AM To: HAPS-L@xxxxxxxxxxx Subject: Re: [HAPS-L] End-product inhibition Biochemistry is full of metabolic pathways where the end product, or even sometimes intermediates, inhibits the first or second enzyme in the pathway. This was always considered to be negative feedback in every text I've ever seen. So, if I understand you correctly, the answer is yes. It's a negative feedback homeostatic mechanism. Harbut, Chester wrote: On a recent essay exam I asked my students to give me an example of negative feedback. Most used parameters such as glucose concentration, temperature, even calcium concentrtion. Two students however used "end-product inhibition" of enzymes (with specific examples). I''m just curious, do most of you consider this negative feedback in the classical sense?
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