Exam 3 comments 2006 - EXAM 3 COMMENTS (2006) Multiple...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
EXAM 3 COMMENTS (2006) Multiple choice (Part I) Total Points = 68; 50 questions Mean Score = 46.66 out of 68 (68.62%) Std. Dev. = 9.64 pts (14.18%) Number of students taking regular exam = 614 Accepted answers (including Alternative Answers in Red ) Essay Questions (Part II) Mean Score Essay A = 6.67, S.D. = 2.63 Mean Score Essay B = 8.06; S. D. = 2.02 Essay A Different organisms sense (1) chemicals in their external environment, (2) hormones circulating in the blood, and (3) neurotransmitters released by nerve terminals, using a single class or “family” of closely related protein molecules. Give an example of one such class of molecules, from one or several organisms and cite specific examples of each of the three types of functions listed above. Explain in general terms the sequence of molecular steps involved in producing a cellular response to each of these signals. Suggested Answer G-protein coupled receptors serve as chemical sensors in yeast cells, in the nose, the tongue, in a variety of plant hormone receptors, and in many eukaryotic cells such as hormone receptors and nerurotransmitter receptors. Hormones like epinephrine, and neurotransmitters like acetyl choline (muscarinic ACh receptor) all affect GPCR’s each in their own way. Rhodopsin, a GPCR in the retina, detects light. G-protein receptors all have 7 trans-membrane domains, all are coupled to a G-protein which is an intracellular molecule. When the G-protein is activated it activates a second # Pts Ans # Pts Ans # Pts Ans # Pts Ans # Pts Ans 1 1 E 11 2 A D 21 1 E 31 1 E 41 2 A 2 1 A 12 2 A 22 1 E 32 1 BC D 42 1 A 3 1 B 13 1 A 23 1 B 33 1 A 43 2 E 4 1 A 14 2 A 24 1 B 34 1 E 44 1 ALL 5 2 C 15 1 D 25 1 A 35 1 B 45 2 B 6 2 D 16 1 E 26 1 B 36 2 A 46 2 D E 7 2 D 17 1 A B 27 2 C 37 2 C 47 2 A 8 1 B 18 1 E 28 1 C 38 2 C 48 1 E 9 1 C 19 1 D 29 1 C 39 2 E 49 1 C 10 1 B 20 1 B 30 2 D 40 1 B 50 2 A
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
BioG 101 Dec. 15, 2006 Cornell University C. D. Hopkins 2 Exam 3-2006 messenger signaling pathway such as cAMP or IP3. In response to the second messenger, the cell produces a complex biochemical responses involving protein kinases. The GPCRs are all related to each other; the genes have undergone descent with modification. Although their functions are diverse, the signaling pathways remain conserved in many diverse cell types. Essay B Plants often evolve anatomical or biochemical adaptations for improving photosynthesis in hot or arid environments. Explain at least three things that plants do differently in these habitats compared to cool and moist environments and explain for each how the structural or molecular changes are adaptive. Suggested Answer (1) Plants conserve water by closing stomata in the daytime when it is dry and hot. This reduces water loss via transpiration. Stomata close automatically when guard cells lose turgor pressure. Unfortunately closing stomata increases photorespiration which breaks down ribulouse 1-6 biphosphate, an intermediate compound in the Calvin cycle. As a
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 11

Exam 3 comments 2006 - EXAM 3 COMMENTS (2006) Multiple...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online