Energy Transfer: Cellular Respiration (CR) and Photosynthesis (PS)

1) What evidence provides support that mitochondria and chloroplasts were once free living prokaryotes?

2) Which of the above organelles are most likely more ancient? Support your answer with evidence with evidence from the geological rock record. (see chapter 25)

3) Compare (and contrast) the overall chemical formulas for both cellular respiration and photosynthesis. Also discuss the similarities and differences between the processes in terms of:

    a) reactants and products, buses (NAD+, FAD, NADP+) is glucose the final product of photosynthesis?

    b) cycles

    c) ATP synthase, chemiosmosis, membranes

    d) structural components of the organelles.

4) DNP (2,4-dinitrophenol),4-Dinitrophenol interfers with ion membrane permeability and was used as a diet aid in the 1930's.  DNP interacts with the inter-membrane by uncoupling the chemiosmotic machinery by making the lipid bilayer of the inner mitochondrial membrane leaky to H+; how does this contribute to weight loss and why DNP is quite dangerous and can lead to death. Who is still using DNP?

5) Why are the following enzymes so important? a) dehydrogenases and b) kinases?

6) Which organisms utilize alcohol fermentation? Lactic Acid fermentation? Why do organisms bother with these processes?

7) Compare substrate level phosphorylation with oxidative phosphorylation.

8) Why is oxygen so important in CR?

9) Why is phosphofructokinase considered the "pacemaker of respiration"? How is CR regulated by feedback mechanisms?(Pg. 181)

10) Compare (and contrast) C3, C4, and CAM photosynthesis. How did photorespiration drive natural selection (evolution) of C4 and CAM?

ECA: Cellular Respiration and Photosynthesis: College Board Standards

2.A.2. Organisms capture, use, and store energy in biological processes such as growth, reproduction and maintaining homeostatic processes.

a. Cellular metabolism captures energy. Evidence of student learning is a demonstrated understanding of the following concepts: 1. Photosynthesis 2. cellular respiration 3. fermentation.

b. Autotrophs capture energy from physical sources in the environment. 1. Photosynthetic organisms capture energy present in sunlight. 2. Chemosynthetic organisms harvest free energy from small molecules present in their environment. c. Heterotrophs capture energy present in carbon compounds produced by other organisms; heterotrophic pathways include cellular respiration and fermentation. Evidence of student learning is a demonstrated understanding of the following concepts:

1. If heterotrophs exhaust their supply of carbohydrates, they may metabolize lipids, proteins, and nucleic acids as sources of energy.

2. Fermentation produces organic molecules, including alcohol and lactic acid, and can occur in the absence of oxygen.

3. Chemosynthesis uses small, inorganic molecules as substrates and can occur in the absence of oxygen. Complete pathways for these processes are out of scope of the course and exam.

 d. Different energy-capturing processes use different terminal electron acceptors. Students should be able to demonstrate understanding of the above concept by using an illustrative example such as: NADP in photosynthesis and Oxygen in cellular respiration.

e. Photosynthesis, chemosynthesis, cellular respiration, and fermentation capture energy in the form of ATP and other small organic molecules.

f. Photosynthesis involves a series of coordinated reaction pathways that capture the free energy present in sunlight (or artificial light sources) to make ATP, NADPH2 and organic sugars. Evidence of student learning is a demonstrated understanding of the following concepts:

1. During photosynthesis chlorophylls absorb energy from light, boosting electrons to a higher energy level in Photosystems I and II.

2. Photosystems I and II are embedded in the internal membranes of chloroplasts and are connected by the exchange of higher free energy electrons through an electron transport chain (ETC).

3. When electrons are transferred between molecules in a sequence of reactions as they pass through the ETC, free energy is extracted by the formation of an electrochemical gradient of hydrogen ion across the membrane by chemiosmosis.

4. The formation of the proton gradient is coupled to the synthesis of ATP from ADP.

5. The energy captured in the light reactions via ATP and NADPH2 is used to produce carbohydrates from carbon dioxide in the Calvin cycle that occurs in the chloroplast.

Memorization of the steps in the Calvin cycle, the structure of the molecules, and the names of enzymes involved are out of scope of the course and exam.

g. Cellular respiration and fermentation involve a series of coordinated enzyme

1. Glycolysis generates ATP by rearranging bonds in glucose molecules.

2. Pyruvate oxidation connects glycolysis to the Krebs cycle by transporting catalyzed reactions that harvest free energy from sugars and other organic molecules. In respiration cells harvest free energy from glucose molecules in four multi-step pathways: glycolysis, pyruvate oxidation, the Krebs cycle, and the electron transport chain. Evidence of student learning is a demonstrated understanding of the following concepts: the two pyruvate molecules produced during glycolysis from the cell cytoplasm to the mitochondrial matrix.

3. In the Krebs cycle pyruvate is oxidized to carbon dioxide, and ATP is synthesized from ADP via substrate-level phosphorylation.

4. Electrons extracted from carbon dioxide in the series of Krebs cycle reactions are carried by NADH and FADH2 to the electron transport chain. Memorization of the steps in glycolysis and the Krebs cycle, or of the structures of the molecules and the names of the enzymes involved, are out of scope of the course and exam.

h. The electron transport chain captures energy from electrons in a series of coupled reactions that establishes an electrochemical gradient across organelle or cellular membranes. Evidence of student learning is a demonstrated understanding of the following concepts:

1. Electron transport chain reactions occur in chloroplasts (photosynthesis), mitochondria (cellular respiration), and plasma membranes (bacteria).

2. Energy trapped in an electrochemical gradient is used to generate ATP via chemiosmosis through ATP synthase.

3. Electrons delivered by NADH and FADH2 are passed to a series of electron accepts as they move toward the final electron acceptor, oxygen.

4. The passage of electrons is accompanied by the formation of a proton gradient across the inner mitochondrial membrane by chemiosmosis, with the membrane separating a region of high proton concentration from a region of low proton concentration.

5. The flow of electrons from the intermembrane space back into the matrix through membrane-bound ATP synthase generates ATP from ADP.

6. As a result of chemiosmosis, free energy captured as ADP is converted to ATP.

7. Decoupling oxidative phosphorylation from electron transport is involved in thermoregulation.

8. The importance of the terminal electron acceptor. The names of the specific electron carriers (i.e. cytochromes) are out of scope of the course and exam.

i. ATP synthesis and degradation is couple to many steps in metabolic pathways. Evidence of student learning is a demonstrated understanding of the following concepts:

1. ATP is produced through the breakdown of organic molecules in cellular respiration and fermentation.

2. ATP is a product of photosynthesis and chemosynthesis

3. ATP can be produced via phosphorylation from phosphate-containing organic molecules.

4. ATP is produced via the movement of H+ ions through ATP synthase.

5. ATP is recycled by phosphorylating ADP. ADP + Pi →ATP.

6. Energy is released for metabolism by the conversion of ATP →ADP.