10/6/2014 1 Energy flow and chemical recycling in ecosystems + JUDGLHQWV Figs. 9.1 & 9.2 ATP (review) $GHQLQH 5LERVH 3KRVSKDWHV Also see Fig. 8.9 ATP hydrolysis provides energy to drive cellular work and energy coupling (review) from Figs. 8.10 & 8.11
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10/6/2014
1
Energy flow and chemical recycling in ecosystems
+�
JUDGLHQWV
Figs. 9.1 & 9.2
ATP (review)
$GHQLQH
5LERVH
3KRVSKDWHV
Also see Fig. 8.9
ATP hydrolysis provides energy to drive cellular work and energy coupling (review)
from Figs. 8.10 & 8.11
10/6/2014
2
• Organic molecules (e.g., glucose, glycogen, starch) “store” energy– arrangement of e- in bonds between atoms (review)
• Enzymes catalyze degradation of organic molecules– from energy rich substrates– to simpler waste products with less energy
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Catabolic pathways – ATP production
• Some release energy ĺ work– remainder ĺ dissipated as heat
• Metabolic pathways that release energy stored in complex organic molecules are catabolic (review)
• Fermentation – one catabolic pathway for ATP production– partial degradation of sugars in absence of oxygen (Anaeorbic
metabolism)
• Cellular respiration - a more efficient and widespread catabolic process for ATP production– Oxygen (O2) is a reactant to complete the
breakdown of organic molecules– Most of process occurs in mitochondria
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Cellular Respiration
• Overall process:– Organic compounds + O2 ĺ CO2 + H2O + Energy– Carbohydrates, fats, and proteins can all be used as fuel
Oxidation and reduction Motivation: In the next severa; lectures, we will go over the primary ways in which cells obtain energy (synthesize ATP!) that is necessary for maintaining life. In the first lecture, we focus on the common theme of oxidation-reduction reactions in these processes. Objectives: ¾ Define oxidation and reduction ¾ Explain how redox reactions are involved in energy exchanges ¾ Write the summary equation for cellular respiration. Write the specific chemical
equation for the degradation of glucose. ¾ Describe the role of NAD+ during respiration
Photosynthesis/chloroplast Fermentation Cellular respiration/Mitochondrion Oxidation Oxidizing agent Reduction Reducing agent Redox Coenzyme Nicotinamide adenine dinucleotide (NAD+/NADH) Dehydragenases (a class of enzymes)
BSC 2010 Chase
Aerobic Respiration Motivation: Aerobic respiration, most of which occurs in mitochondria, is the most efficient metabolic pathway for ATP production. Objectives: ¾ Name the three stages of cellular respiration and state the region of the eukaryotic cell
where each stage occurs. ¾ Describe how the carbon skeleton of glucose changes as it proceeds through glycolysis. ¾ Explain why ATP is required for the preparatory steps of glycolysis. ¾ Identify where substrate-level phosphorylation and the reduction of NAD+ occur in
glycolysis. ¾ Describe where pyruvate is oxidized to acetyl CoA, what molecules are produced, and
how this process links glycolysis to the citric acid cycle. ¾ List the products of the citric acid cycle. Explain why it is called a cycle. ¾ Distinguish between substrate level phosphorylation and oxidative phosphorylation. ¾ Explain where and how the respiratory electron transport chain creates a proton
gradient. ¾ Describe the structure and function of the four subunits of ATP synthase. ¾ Summarize the net ATP yield from the oxidation of a glucose molecule (include
coenzyme production during glycolysis and cellular respiration). Oxidative phosphorylation Substrate-level phosphorylation Kinase (a class of enzymes) Glycolysis (10 steps) Energy investment and payoff phases Intermediates Pyruvate Citric acid cycle, also known as the Krebs cycle (8 steps) Acetyl coenzyme A (acetyl CoA) Intermediates
BSC 2010 Chase
Electron transport chain NADH/FADH2
Cytochromes O2
Chemiosmosis Proton-motive force (electrochemical gradient for H+) ATP synthase Rotor Stator Rod (stalk) Knob (catalytic sites for ADP phosphorylation)
BSC 2010 Chase
Anaerobic metabolism Motivation: Anaerobic respiration is a metabolic pathway for ATP production in the absence of oxygen. It is commercially important, and was significant in early evolution because oxygen was not a significant part of the earth’s atmosphere. Objectives: ¾ State the basic function of fermentation. ¾ Compare what happens to pyruvate in alcohol fermentation and lactic acid fermentation. ¾ Compare the processes of fermentation and cellular respiration. ¾ Describe the evidence that that suggests that glycolysis is an ancient metabolic
pathway. (Connecting glycolysis and the citric acid cycle to other metabolic pathways) ¾ Describe how food molecules other than glucose can be oxidized to make ATP. ¾ Explain how glycolysis and the citric acid cycle can contribute to anabolic pathways. ¾ Explain how ATP production is controlled by the cell and describe the role that the
allosteric enzyme phosphofructokinase plays in the process. Alcohol fermentation Acetaldehyde Ethanol Lactic acid fermentation Lactate Facultative anaerobes