Cellular Respiration: Harvesting Chemical Energy:

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1. Energy Flow and Chemical Cycling in the Biosphere.

Diagram the flow of energy and cycling of chemicals in ecosystems, See figure 6.3

Define the following terms related to ecosystems and modes of nutrition:

• photosynthesis
• autotrophs
• heterotrophs
• producers
• consumers

Comment: autotrophs come in two types: photosynthetic autotrophs rely on sunlight as a source of energy. They include plants, certain protists and some bacteria, especially cyanobacteria. chemosynthetic autotrophs rely on simple inorganic molecules such as hydrogen, hydrogen sulfide,nitrogen compounds or even Fe++ ions as a source of energy and hence do not rely on sunlight at all. Many members of the Domain Archaea are chemosynthetic autotrophs.

2. Overview of cellular respiration:

• Give the overall equation for aerobic cellular respiration of glucose.
• Explain the role of oxygen in aerobic cellular respiration. See fig 6.6
• Define redox reaction in terms of electron transfer.
• Diagram cellular respiration as a set of redox reactions. See p 91 bottom.
• Explain the role of NAD+ and other electron acceptors in cellular respiration
• Explain the function and location of electron transport systems in the mitochondrion.

3. The Metabolic pathway of cellular respiration.

• Starting with glucose as a substrate, list the location, reactants and products of each of the three main stages in cellular respiration:
  • Glycolysis
  • The Kreb's cycle
  • Electron Transport
• Explain how the electron transport chains drive ATP synthesis in the mitochondrion.
• Study fig 6.12 carefully and be able to list the five steps involved in ATP synthesis in the mitochondrion.
• Explain the specific role of the electron transport chain, hydrogen pumps, hydrogen ions and ATP synthase in ATP production.
• Tell the function of oxygen in ATP synthesis.

Glycolysis in cytoplasm

Kreb's Cycle in matrix of mitochondrion

Electron Transport Phosphorylation

Comment! Note that cells make ATP by two processes.

• Substrate level phosphorylation. This is direct phosphate transfer from an organic molecule to ADP as shown in figure 6.9. This is probably the original way cells made ATP. All cells can do this in glycolysis and the little bit of ATP made directly in the Kreb's cycle is made this way.
• Electron transfer phosphorylation. Electron transport systems power production of ATP from ADP and inorganic phosphate. See figure 6.12. This is the way many cells make most of their ATP.

4. Explain the five big steps in electron transport phosphorylation

1. NADH and FADH2 donate electrons to electron transport chains

2. Electron transport chains pump H+ to outer compartment of mitocondrion

3. H+ Diffuse to inner compartment through ATP synthase channels

4. ATP synthase catalyzes production of ATP from ADP + Pi(inorganic phosphate)

5. Electrons from the Electron transport chains are accepted by oxygen along with hydrogen ions to make water.

5. Define and explain anaerobic respiration

• Define fermentation
• Explain the function of fermentation. See figure 6.15
• Explain the importance of lactate fermentation in humans
• Distinguish between facultative anaerobes and obligatory anaerobes.

Comment: Fermentation is not the only type of anaerobic respiration. Certain bacteria are able to produce ATP via electron transport in the absence of oxygen. They do this by using some other electron acceptor. For common alternatives include carbon dioxide or nitrate or sulfate ions. Also note the text's comments about glycolysis being the most wide spread metabolic pathway common to all cells. This suggests that glycolysis evolved very early in the evolution of life and the other stages of cellular respiration developed later.

Terms:

pgd 09/19/02 revised 09/21/06