Cellular Energy: Respiration Anaerobic respiration Goals: Define and describe the 3 sets of chemical reactions that comprise aerobic cellular respiration Describe the types of anaerobic respiration Compare anaerobic and aerobic cellular respiration Use knowledge of cellular respiration to solve problems related to human health and disease Cellular respiration and photosynthesis are chemical reactions that provide kinetic and potential energy for cells H O Sunlight energy Photosynthesis in chloroplasts CO + + Cellular respiration in mitochondria O Is photosynthesis exergonic or endergonic? Endergonic it absorbs energy from the environment and stores it as potential energy in sugar Is cellular respiration exergonic or endergonic? ATP Exergonic it breaks chemical bonds to release potential energy into kinetic energy (for cellular work) Heat energy 1
Respiration converts potential energy in glucose into kinetic energy + potential energy in ATP C 6 H 1 O 6 + 6 O 6 CO + 6 H O + ATPs Oxygen Carbon dioxide Water Accessible Potential Energy 40% of glucose energy is made into ATP, the molecule cells use to do work 60% of glucose energy is released as heat Respiration is a series of redox reactions Redox chemical reactions involve the movement of electrons from one molecule to another molecule! OIL RIG: Oxidation Is Loss, Reduction Is Gain Oxidation=LOSS of electrons Reduction = GAIN of electrons Loss of hydrogen atoms (oxidation) C 6 H 1 O 6 + 6 O Gain of hydrogen atoms (reduction) 6 CO + 6 H O + Energy (ATP) Respiration is a series of redox reactions Oxidation Dehydrogenase Reduction NAD + + H NADH + H + H + + e (carries electrons) NAD + /NADH is the main electron carrier that is reduced during cellular respiration FAD+/FADH is another important electron carrier
Cellular respiration occurs in 3 stages 1- Glycolysis. - Citric acid cycle. 3- Oxidative phosphorylation. Stage 1: Glycolysis Glycolysis is a set of 9 enzyme-driven chemical reactions, collectively called a metabolic pathway. Glycolysis occurs in the cytoplasm. Glycolysis does not use oxygen. The net molecular products of glycolysis of 1 glucose are: - pyruvate - ATP - +H Stage 1: Glycolysis Draw arrows indicating the reactants and products. ATP is formed by substrate level phosphorylation and can be used for work. Reactant ADP + P NAD + ATP + H + Product Pyruvate 3
Substrate-Level Phosphorylation: the formation of ATP by the direct transfer of a phosphate group to ADP Enzyme Enzyme P ADP + ATP P Substrate P Product Transfer of a phosphate group from a substrate to ADP Generates molecules of ATP Stage 1: Glycolysis Some kinetic energy is released NAD+ is reduced to NADH. NADH, H+, and pyruvate are used in the next stages of respiration: NADH + H oxidative phosphorylation pyruvate fermentation or citric acid cycle. Reactant ADP + P ATP + H + Product Pyruvate 4
Lactic Acid Fermentation Alcoholic Fermentation Pyruvate Lactate Pyruvate Ethanol + CO Glycolysis Alcoholic Fermentation Lactic Acid Fermentation Citric Acid Cycle Oxidative Phosphorylation Location Aerobic or anaerobic Reactants Products Number of ATP produced Fermentation is anaerobic respiration Anaerobic cellular respiration happens temporarily in our muscle cells, when the need for ATP is greater than the amount of oxygen we can deliver to our mitochondria. The metabolic pathway utilized to generate ATP is glycolysis. Obligate anerobes: oranganisms that require anaerobic conditions, O is toxic Facultative anerobe: organisms that can make ATP by both fermentation and oxidative phosphorylation depending on the availability of O. 5
ADP + P ATP GLYCOLYSIS Pyruvate 1) Lactic acid fermentation - Bacteria (yogurt and cheese). -Our tired-out muscle cells. NAD+ must be around as an electron acceptor! Lactate NAD+ is regenerated during lactic acid fermentation in order to keep glycolysis running!! Lactic Acid Fermentation Alcoholic Fermentation Pyruvate Lactate Pyruvate Ethanol + CO ADP + P ATP CO released GLYCOLYSIS Pyruvate ) Alcohol fermentation Yeast (beer and wine) NAD+ is regenerated during alcohol fermentation in order to keep glycolysis running!! Ethanol 6
Lactic Acid Fermentation Alcoholic Fermentation Pyruvate Lactate Pyruvate Ethanol + CO Diagram the pathway that produces and then breaks down lactic acid the working muscles generate energy anaerobically. This energy comes from glucose through a process called glycolysis, in which glucose is broken down or metabolized into a substance called pyruvate through a series of steps. When the body has plenty of oxygen, pyruvate is shuttled to an aerobic pathway to be further broken down for more energy. But when oxygen is limited, the body temporarily converts pyruvate into a substance called lactate, which allows glucose breakdown--and thus energy production--to continue. The working muscle cells can continue this type of anaerobic energy production at high rates for one to three minutes, during which time lactate can accumulate to high levels. Once the body slows down, oxygen becomes available and lactate reverts back to pyruvate, allowing continued aerobic metabolism and energy for the body s recovery from the strenuous event. Lactic acid is actually a fuel, not a caustic waste product. Muscles make it deliberately, producing it from glucose, and they burn it to obtain energy. The reason trained athletes can perform so hard and so long is because their intense training causes their muscles to adapt so they more readily and efficiently absorb lactic acid. Assignments: Fill in the diagram and table worksheets each worksheet will count as 1 quiz grade for a total of quiz grades. Re-draw the diagrams of glycolysis and both forms of fermentation from your notes 7