11. Fill in the following table with the carbon source and energy source of each
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11. Fill in the following table with the carbon source and energy source of each type of organism Organism Carbon Source Energy Source Photoautotroph Photoheterotroph Chemoautotroph Chemoheterotroph 12. Define oxidation-reduction, and differentiate between the following terms: a. b. c. Aerobic and anaerobic respiration Respiration and fermentation Cyclic and noncyclic photophsphorylation 13. The pentose phosphate pathway produces only one ATP. List three advantages of this pathway for the cell. 14. Compare and contrast carbohydrate catabolism and energy production in the following bacteria: a. b. c. Pseudomonas, an acrobic chemoheterotroph Spirulina, an oxygenic photoautotroph Ectothiorhodospira, an anoxygenic photoautotroph you were engaged in developing new antimicrobial drugs, how might you proceed to develop new enzyme inhibiting drugs? 15. Many of the drugs we use to combat infections by microorganisms act as enzyme inhibitors. IfExplanation / Answer
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12. Cellular respiration involves many reactions in which electrons are passed from one molecule to another. Reactions involving electron transfers are known as oxidation-reduction reactions (or redox reactions).
You may have learned in chemistry that a redox reaction is when one molecule loses electrons and is oxidized, while another molecule gains electrons (the ones lost by the first molecule) and is reduced.
The formation of magnesium chloride is one example of a redox reaction
Mg + Cl2 Mg2+ + 2Cl-
In this reaction, the magnesium atom loses two electrons, so it is oxidized. These two electrons are accepted by chlorine, which is reduced.
Oxidation and reduction reactions are fundamentally about the transfer and/or hogging of electrons. However, in the context of biology, there is a little trick we can often use to figure out where the electrons are going. This trick lets us use the gain or loss of H and O atoms as a proxy for the transfer of electrons.
In general:
If a carbon-containing molecule gains H atoms or loses O atoms during a reaction, it’s likely been reduced (gained electrons or electron density)
On the other hand, if a carbon-containing molecule loses H atoms or gains O atoms, it’s probably been oxidized (lost electrons or electron density)
For example, let’s go back to the reaction for glucose breakdown:
C6H12O6 + 6O2 6CO2 + 6H2O
In glucose, carbon is associated with H atoms, while in carbon dioxide, it is not associated with any Hs. So, we would predict that glucose is oxidized in this reaction. Similarly, the O atoms in O2 end up being associated with more Hs after the reaction than before, so we would predict that oxygen is reduced.
a. Both aerobic and anaerobic respiration involve chemical reactions which take place in the cell to produce energy, which is needed for active processes.
Aerobic respiration takes place in the mitochondria and requires oxygen and glucose, and produces carbon dioxide, water, and energy. The chemical equation is C6H12O6 + 6O2 6CO2 + 6H2O (glucose + oxygen -> carbon dioxide + water).
Anaerobic respiration also produces energy and uses glucose, but it produces less energy and does not require oxygen. This is useful in tissues which have a high energy demand such as in working muscles, in which there is not enough oxygen to produce all the energy needed by using aerobic respiration alone. Anaerobic respiration takes place in the cell cytoplasm and produces lactic acid. The chemical equation is C6H12O6 -> 2C3H6O3 (Glucose -> Lactic acid). The lactic acid then needs to be oxidised later to carbon dioxide and water afterwards to prevent it building up. This process requires oxygen and therefore following anaerobic respiration there is oxygen debt in the cell, as oxygen is needed to break down the lactic acid produced.
b. Fermentation and cellular respiration differ in that fermentation does not require oxygen while cellular respiration does. Fermentation and cellular respiration are also different because water molecules are not produced during fermentation but are produced during cellular respiration. All fermentation reactions occur in the cell's cytoplasm but during cellular respiration, only glycolysis occurs in the cytoplasm. Lastly, fermentation produces a net gain of 2 ATPs while cellular respiration produces a net gain of 32 ATPs.
c. Noncyclic photophosphorylation produces 1 molecule of ATP and 1 molecule of NADPH per electron pair; however, carbon fixation requires 1.5 molecules of ATP per molecule of NADPH. To address this issue and produce more ATP molecules, some plant species use a process known as cyclic photophosphorylation. Cyclic photophosphorylation involves only photosystem I, not photosystem II, and does not form NADPH or O2. In cyclic phosphorylation, high-energy electrons from photosystem I are transferred to the cytochrome b6-f complex instead of being transferred to NADP+. The electrons lose energy as they are passed through the cytochrome b6-f complex back to the chlorophyll of photosystem I and H+ is pumped across the thylakoid membrane as a result. This increases the concentration of H+ in the thylakoid space, which drives the production of ATP by ATP synthase.
The level of noncyclic versus cyclic photophosphorylation that occurs in a given photosynthetic cell is regulated based on the cell’s needs. In this way, the cell can control how much light energy it converts into reducing power (fueled by NADPH) and how much is converted into high-energy phosphate bonds (ATP).
13. Three advantages of pentose phosphate pathway are
Organism Carbon source Energy source Photoautotroph Carbon dioxide Sunlight Photoheterotroph Organic compounds from the environment like carbohydrates, fatty acids, and alcohols Sunlight Chemoautotroph Their carbon source is derived from sulfur, carbohydrates, lipids, and proteins. Inorganic energy sources such as hydrogen sulfide, elemental sulfur, ferrous iron, molecular hydrogen, and ammonia. Chemoheterotroph Gets organic carbon from the breakdown of other organic matter. Gets energy through the breakdown of organic molecules like sugarRelated Questions
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