BILD 1 Oct. 28, 2003
Schmidt Answers
PROBLEM SET #3
1. Identify three key components of mitochondria that are essential for the production of ATP and state why they are important.
1) Electron transport chain: Creates proton gradient
2) Inner membrane: Provides barrier so proton gradient can form.
3) H+-ATP synthase Synthesizes ATP using proton gradient.
2. Describe the role/function in photosynthesis of each of the following and where they are located in the cell: (1) NADPH, (2) RUBISCO, (3) thylakoid membranes, (4) grana, (5) stroma, (6) chlorophyll.
NADPH: made during light reaction, carries reducing power to dark
reactions (stroma).
RUBISCO: enzyme that fixes CO2 in dark reaction (stroma).
Thylakoid membranes: make up grana where photosynthetic reaction
centers for light reactions are located, serves as barrier for
proton gradient (grana).
Grana: stacks of thylakoid membranes for light reaction (chloroplast)
Stroma: fluid surrounding grana where dark reactions occur (").
Chlorophyll: light harvesting pigment in thylakoid membranes.
3. Certain compounds called uncouplers (eg. dinitrophenol) prevent the synthesis of ATP in mitochondria. They do not interfere with the passage of electrons down the electron transport chain to oxygen, but they can shuttle protons across a membrane. How might these uncouplers prevent ATP synthesis?
ATP synthesis requires a proton gradient across the inner membrane of the mitochondria. Uncouplers release the gradient by shuttling protons across the membrane and thus prevent ATP from being made.
4. The Krebs cycle and the Calvin cycle play important roles in cells. Where in the cell do these cycles occur? Can the Krebs cycle and the Calvin cycle occur in the same cell? What are the key molecules that store or provide chemical energy for these cycles?
Calvin cycle occurs in the stroma of the chloroplast, and the Krebs cycle occurs in the matrix of the mitochondria. These cycles both occur in green plant cells.
Krebs cycle stores energy in ATP, NADH, FADH2 by oxidizing pyruvate. Calvin cycle uses energy stored in ATP and NADPH to synthesize carbohydrates.
5. What are the light and dark reactions of photosynthesis and how are they related?
Light reactions capture solar energy in the thylakoid membranes and synthesize NADPH and ATP. The dark reactions fix CO2 and synthesize sugars in the stroma. Light and dark reactions are related by the fact that both (1) occur in the chloroplast and (2) involve the compounds NADPH and ATP, the light reactions produce them (from NADP+ and ADP) and the dark reactions use them.