quiz3_s - MIT Department of Biology 7.014 Introductory...

Info iconThis preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon
MIT Department of Biology 7.014 Introductory Biology, Spring 2005 7.014 Quiz III Solutions Class Average = 61.8 Median = 62 Grade Range % A 80 - 100 10 B 68 - 79 43 C 49 - 61 27 D 37 – 48 9 F 0 – 36 8
Background image of page 1

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

View Full DocumentRight Arrow Icon
Name:________________________________________ TA:____________________ Question 1 (20 points) The table below lists types of metabolism in the left column. Type of metabolism Electron source Carbon source Energy source fermentation sugar sugar sugar sulfur oxidation chemosynthesis H 2 S CO 2 heat, H 2 S oxygenic photosynthesis H 2 O CO 2 light anaerobic respiration sugar sugar sugar nitrification chemosynthesis NH 3 CO 2 heat, NH 3 aerobic respiration sugar sugar sugar anoxygenic photosynthesis H 2 S CO 2 light a) For each type of metabolism, i) use the following list to fill in Electron source (column 2) and Carbon source (column 3) in the table above. A. sugar (Note, “sugar” here is a generic term for any organic carbon compound (CH 2 O) n ). B. Water (H 2 O) C. hydrogen sulfide (H 2 S) D. methane (CH 4 ) E. carbon dioxide (CO 2 ) F. NH 3 ii) fill in Energy source (column 4) in the table above. For this part, you are not limited to the list above. b) For a number of the metabolisms above, the electron source is the same as the energy source. Explain why they are not the same for photosynthesis. The energy source in photosynthesis is light. While other energy sources are also sources of electrons (e.g. sugar), the energy source of photosynthesis, light, does not contain electrons. Therefore, organisms using light as an energy source must use a different source of electrons. donor c) Organisms carrying out respiration need a final electron acceptor to keep the electron transport chain (ETC) functional. (Circle the correct term above.) Explain how this compound enables the ETC to remain functional. The final electron acceptor removes the electrons after they have traveled the length of the ETC. This then frees the last protein in the ETC to pull the next pair of electrons from the next to last protein in the chain. The newly freed protein can in turn pull the electrons from (only slightly) less electronegative protein. If no final acceptor existed, the ETC would get “backed up” by accumulating electrons to capacity on ever less electronegative proteins. This back up would propagate to eventually saturate all proteins in the chain. Having a final electron acceptor relieves this potential problem. 2
Background image of page 2
Name:________________________________________ TA:____________________ Question 1, continued d) Using an argument based on redox and energetics, explain how aerobic respiration generates more ATP per molecule of glucose than anaerobic respiration. O 2 is the electron acceptor used in aerobic respiration. All the possible electron acceptors used in anaerobic respiration are less electronegative than O 2 . That means that each of these acceptors would operate with a shorter electron transport chain than O 2 . A shorter chain would include fewer proton
Background image of page 3

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

View Full DocumentRight Arrow Icon
Image of page 4
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 10

quiz3_s - MIT Department of Biology 7.014 Introductory...

This preview shows document pages 1 - 4. Sign up to view the full document.

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