Cellular Energy: Respiration. Goals: Aerobic cellular respiration occurs in 3 stages. Aerobic respiration

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1 Cellular Energy: Respiration Aerobic respiration Goals: Define and describe the 3 sets of chemical reactions that comprise aerobic cellular respiration Describe the 2 types of anaerobic respiration Compare anaerobic and aerobic cellular respiration Use knowledge of cellular respiration to solve problems related to human health and disease Aerobic cellular respiration occurs in 3 stages 1- Glycolysis. 2- Citric acid cycle. 3- Oxidative phosphorylation. 1

2 Review Stage 1: Glycolysis Reactants Glucose, 2 ADP, 2 P, 2 NAD+ Products 2, 2 NADH+H, 2 Pyruvate 2 42 ADP + 42 P Glucose 2 NAD + 2 NADH is formed by. Substrate level phosphorylation NAD+ is to REDUCED NADH. INITIAL INVESTMENT = 2 TOTAL PRODUCED = 4 NET PRODUCED = Pyruvate 2 ADP + 2 P 2 Glucose GLYCOLYSIS 2 Pyruvate Review Anaerobic Respiration 2 NAD + 2 NADH 2 NADH 2 NAD + LACTIC ACID or ALCOHOLIC fermentation NADH+H from glycolysis is OXIDIZED back to NAD+ 2 ADP + 2 P 2 2 CO 2 released Glucose GLYCOLYSIS 2 Pyruvate 2 NAD + 2 NADH 2 NADH 2 NAD + 2 Lactate 2 Ethanol The citric acid cycle completes the oxidation of glucose in aerobic cellular respiration 2

3 Stage 2: Citric acid cycle A set of 5 enzyme-driven chemical reactions, collectively called a metabolic pathway. Occurs in the mitochondria (within the matrix and inner membrane). Does not use oxygen. The net molecular products of the citric acid cycle for 1 glucose molecule are: - 4 CO 2-6 NADH - 2 FADH - 2 Pyruvate from glycolysis is first groomed The pyruvate molecules produced by glycolysis are modified after being transported into the mitochondria. - One carbon is removed as CO 2 - One electron is removed when NAD + is reduced to NADH - The compound coenzyme A is added to make acetyl coenzyme A (acetyl ) 2 made per original glucose Stage 2: The Citric Acid Cycle Two carbons (acetyl) are carried to the start of the cycle by coenzyme A 2 CO 2, 1 FADH 2, and 1 exit the cycle How many pyruvates (and therefore acetyle s) per glucose? 2! 3

4 Stage 2: The Citric Acid Cycle Oxaloacetate Acetyl 2 carbons enter cycle 1 CITRIC ACID CYCLE Step 1 Acetyl stokes the furnace. Stage 2: The Citric Acid Cycle Oxaloacetate Acetyl 2 carbons enter cycle 1 Citrate NAD + CITRIC ACID CYCLE 2 NAD CO 2 leaves cycle ADP + P Alpha-ketoglutarate 3 CO 2 leaves cycle NADH + NAD + Step 1 Acetyl stokes the furnace. Steps 2 3 NADH,, and CO 2 are generated during redox reactions. Stage 2: The Citric Acid Cycle Oxaloacetate Acetyl 2 carbons enter cycle 1 Citrate NAD NAD + Malate 5 CITRIC ACID CYCLE 2 NAD + NAD CO 2 leaves cycle ADP + P FADH 2 4 Alpha-ketoglutarate FAD 3 Succinate CO 2 leaves cycle NADH + NAD + Step 1 Acetyl stokes the furnace. Steps 2 3 NADH,, and CO 2 are generated during redox reactions. Steps 4 5 Redox reactions generate FADH 2 and NADH. 4

5 Lactic Acid Fermentation Alcoholic Fermentation 2 Pyruvate 2 Lactate 2 NADH 2 NAD+ OR 2 Pyruvate 2 Ethanol + 2 CO 2 2 NADH 2 NAD+ Stage 3: Oxidative phosphorylation Produces lots of (about 32) by capturing the energy from electron carriers (NADH and FADH 2 ) generated in the first two steps of cellular respiration. Occurs in the mitochondria (across the inner membrane and in the intermembrane space) Involves the electron transport chain and chemiosmosis Transfers electrons to the terminal electron acceptor oxygen. Intermembrane space Intermembrane space Protein complex of electron carriers Electron carrier synthase Inner mitochondrial membrane Mitochondrial matrix FADH Electron 2 FAD flow NADH NAD H 2 O O ADP + P Electron Transport Chain Chemiosmosis OXIDATIVE PHOSPHORYLATION 5

6 Stage 3a: The electron transport chain The e -s associated with the coenzymes NADH and FADH 2 have a lot of potential energy. They give up small bits of their potential energy to protein complexes in the inner mitochondrial membrane. Electrons from glucose fall down an energy staircase NADH NAD + + 2e Electron transport chain Controlled release of energy for synthesis of 2e 1 2 O 2 H 2 O Stage 3a: The electron transport chain The e -s associated with the coenzymes NADH and FADH 2 have a lot of potential energy. They give up small bits of their potential energy to protein complexes in the inner mitochondrial membrane. Some of these complexes use this energy to pump ions across the membrane into the intermembrane space against their concentration gradient. e -s are transferred from membrane protein to membrane protein, giving up some of their energy with each transfer. 6

7 Stage 3a: The electron transport chain The final e - acceptor molecule is oxygen. - Each molecule of O2 picks up 2 H+ to form H2O. Without oxygen at the end to pull the e -s down the transport chain the earlier steps do not occur i.e. no ion gradient is formed across the membrane. Stage 3b: synthase Enzyme complexes in the inner membrane called synthases use the potential energy of the H+ ion gradient to phosphorylate ADP to. H+ ions flow through a channel in the synthase protein complex and, which energize it to produce. This is called chemiosmosis. Lactic Acid Fermentation Alcoholic Fermentation 2 Pyruvate 2 Lactate 2 NADH 2 NAD+ OR 2 Pyruvate 2 Ethanol + 2 CO 2 2 NADH 2 NAD+ 7

8 Which type of skeletal muscle fibers will have more mitochondria? Slow Twitch (Type I) The slow muscles are more efficient at using oxygen to generate more fuel (known as ) for continuous, extended muscle contractions over a long time. They fire more slowly than fast twitch fibers and can go for a long time before they fatigue. Therefore, slow twitch fibers are great at helping athletes run marathons and bicycle for hours. Fast Twitch (Type II) Because fast twitch fibers use anaerobic metabolism to create fuel, they are much better at generating short bursts of strength or speed than slow muscles. However, they fatigue more quickly. Fast twitch fibers generally produce the same amount of force per contraction as slow muscles, but they get their name because they are able to fire more rapidly. Having more fast twitch fibers can be an asset to a sprinter since she needs to quickly generate a lot of force. 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. Cells can use other organic molecules as fuel for cellular respiration. 8

9 Food, such as peanuts! Carbohydrates Fats Proteins Sugars Glycerol Fatty acids Amino acids Amino groups Glucose G3P Pyruvate GLYCOLYSIS Acetyl CITRIC ACID CYCLE OXIDATIVE PHOSPHORYLATION (Electron Transport and Chemiosmosis) Organic molecules also provide raw materials for biosynthesis. Biosynthesis of raw materials from food molecules CITRIC ACID CYCLE Acetyl GLUCOSE SYNTHESIS Pyruvate G3P Glucose Amino groups Amino acids Fatty acids Glycerol Sugars Uses! Proteins Fats Carbohydrates Cells, tissues, organisms 9

10 Supply and demand regulation Cellular respiration: If accumulates in a cell to high levels, the excess will inhibit glycolysis, slowing down respiration, and thus conserving resources. This type of regulation is called feedback inhibition. Feedback inhibition also regulates biosynthesis. Cellular Respiration A Case Study The Case You re working at the medical examiner s office at San Francisco County Hospital. It has been a particularly light day. Just as you re flipping the switch, you get a call from your secretary. Francesca, he says. We ve got a dead kid up here that you ll want to look at right away. Might be foul play. Thinking of your four-year old daughter waiting for you at home, you grimace. OK Jon, I m heading to the morgue. Performing autopsies on kids is the least favorite part of your job. But you are paid to solve medical mysteries, and it looks like you ve got one here. 10

11 The Case II In the morgue, you find the report from the hospital. Glancing over it, you notice a narrative of the girl s last hours and read it carefully: At 10 AM, mother returns from the store to find girl vomiting, not feeling well, and sleepy. Mother put girl to bed. Ten minutes later, she noticed that the child s breathing became irregular and slow. She tried to wake her daughter but was not able to do so. The child became comatose. At noon, the girl was admitted to the hospital, with no heartbeat or spontaneous breathing. A police report states the following: The parents discovered that the girl had been giving her dog a bath using a flea dip called Fleacide. According to the label on the container, Fleacide is an insecticide made of plant material only and appropriate for external use on animals. New & Improved!! FLEACIDE Flea dip Kills fleas & Chewing Lice on contact! Guaranteed! Instructions for use: Add 1/3 cup per tub of full water. Dunk dog. Rinse. Repeat if necessary. Active Ingredients: Rotenone: CAS# % essential oils of clove. 2.0% essential oil of cinnamon.2.0 % essential oil of fir..2.0% essential oil of rosemary..2.0% Inert ingredients 85.0% Made from all natural products! Non-toxic. 1.) What could have been in the flea dip that killed the girl? 2.) How can a product that is normally harmless to humans and pets killed the girl? 3.) Is the label misleading? Why? Autopsy Report The girl died within two hours of first vomiting Immediate cause of death was hypoxia Tissue sections from the kidneys, lungs, thymus, and heart show massive cell death Staining with cellular dyes indicates that the mitochondria within the affected tissues were damaged Hypoxia: is a pathological condition in which the body as a whole (generalized hypoxia) or a region of the body (tissue hypoxia) is deprived of adequate oxygen supply. 11

12 Normal Necrotic Cellular Staining Kidney Liver Lung Given the autopsy report, and recalling your knowledge from your reading about the functions of cellular organelles, what functions of the cell did fleacide affect? As the medical examiner, what other information would you want to know? Analysis A more detailed analysis of the cells from the girls heart, showed that levels were reduced in the mitochondria. levels in the cytoplasm of these cells, however, was normal. What cellular process (or processes) was impaired by the Fleacide? 12

13 Cellular respiration (aerobic) occurs in 3 stages Intermembrane space Protein complex of electron carriers Electron carrier synthase Inner mitochondrial membrane Mitochondrial matrix FADH Electron 2 FAD flow NADH NAD H 2 O O ADP + P Electron Transport Chain Chemiosmosis OXIDATIVE PHOSPHORYLATION Using a new chromatographic technology developed late last year, you are able to determine the levels of various subcellular components in the heart cells. 13

14 Chromatography: is the collective term for a family of laboratory techniques for the separation of mixtures. Gas chromatography Thin layer chromatography Subcellular Analysis Metabolite Autopsy Finding Normal Levels Glucose 102 mmol 100 mmol Pyruvate 23 mmol 25 mmol NAD+ 6 mmol 75 mmol NADH 383 mmol 50 mmol 1. Given this new information, what specific cellular process do you think was affected by the Fleacide? Why? 2. Would artificial respiration or oxygenation save the girl? Why or why not? Intermembrane space Protein complex of electron carriers Electron carrier synthase Inner mitochondrial membrane Mitochondrial matrix FADH Electron 2 FAD flow NADH NAD H 2 O O ADP + P Electron Transport Chain Chemiosmosis OXIDATIVE PHOSPHORYLATION 14

15 Rotenone Cyanide, carbon monoxide Oligomycin synthase DNP FADH 2 FAD NADH NAD O H 2 O ADP + P Electron Transport Chain Chemiosmosis Rotenone Rotenone is a natural plant toxin used for centuries by indigenous peoples of Southeast Asia and South America Rotenone is chemically unstable and breaks down rapidly in the environment, yielding water soluble non-toxic products. Rotenone is a highly specific metabolic poison that affects cellular aerobic respiration, blocking mitochondrial electron transport 15