Chapter 7 - BSC 1010 Dr. Presley Chapter 7 CELLS HARVEST...

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BSC 1010 Dr. Presley Chapter 7 CELLS HARVEST CHEMICAL ENERGY Cells produce energy Review material from Chapter 6 Notes on energy and energy conversions Types of metabolism: catabolism and anabolism ATP is used to drive cellular work The recycling of ATP (Fig 6.6 on page 112) Active muscle cells use 10 million ATPs per second Ways cells make ATP: Phosphorylation - addition of phosphate group to compound. ADP + P i + energy —> ATP types: substrate- , oxidative- , photophosphorylation occurs in cytosol, mitochondrial matrix, stroma of chloroplast Chemiosmosis - occurs on inner mitochondrial membrane, thylakoid membrane of the chloroplast (Chapter 8) coenzymes and cytochromes provide energy to pump protons across membrane creating an electro-chemical gradient process in which energy is released when protons move along a gradient resulting in synthesis of ATP HOW DO CELLS USE ENERGY STORED IN FOOD TO MAKE ATP? Metabolic pathways - many steps are involved in the energy conversion in order to release only small units of energy along these steps instead of one big burst - controlled by specific enzymes with allosteric regulation - these metabolic pathways are similar in all organisms - Bomb calorimeter is an instrument which can oxidize glucose with an explosive release of a large amount of energy all at once (i.e. highly exergonic with a ΔG = -686 kcal/mol.). A single release of this much energy from glucose could not be managed by the cell at one time. The living system will release the stored energy in the chemical bonds of glucose in small amounts during a sequence of enzymatically controlled steps. These small amounts of energy released are of manageable quantities for the cell to handle. - the transfer of electrons can provide energy during chemical reactions - complete breakdown of glucose required the presence of oxygen gas and involves the four following steps: glycolysis, and the three steps of cellular respiration: pyruvate oxidation (transition reaction), Krebs Cycle, Respiratory Chain (electron transport system) See Figure 7.5 a, p. 128 - incomplete breakdown of glucose occurs when oxygen gas is not available and involves the two following steps: glycolysis and fermentation (alcoholic or lactate) See Figure 7.5 b, p. 128 - both prokaryotic and eukaryotic cells can perform this energy conversion, - Note the location of the metabolic processing in each cell type. - Study Table 7.1 on page 128 - Oxidation-reduction reactions (redox reactions) Study Fig. 7.2, p. 127 - these reactions transfer electron(s) from one reactant to another - this chemical conversion also involves changes in energy *Oxidation = loss of electrons (or Hydrogen atom) from a substance *Reduction = gain of electrons (or Hydrogen atom) by a substance - the electron donor is called the reducing agent and will become oxidized - the electron acceptor is called the oxidizing agent and will become reduced **because oxygen is so electronegative, it is a powerful oxidizing agent, note that as it becomes reduced by the addition of electrons, protons will also flow often resulting in the formation of water
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Chapter 7 - BSC 1010 Dr. Presley Chapter 7 CELLS HARVEST...

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