Chapter 9: Cellular Respiration Energy flows into an ecosystem as sunlight and ultimately leaves as heat, while the chemical elements essential to life are recycled

Catabolic Pathways  Fermentation (anaerobic) Catabolic process; the partial degradation of sugars that occurs without the use of oxygen  Cell Respiration (aerobic) Catabolic process; complete degradation of organic fuels; most prevalent and efficient; oxygen is consumes as a reactant along with organic fuel; occurs in the mitochindria Organic Compounds + O 2  CO 2 + H 2 O + Energy Yield energy by oxidizing organic fuels  Catabolism is linked to work by a chemical drive shaft - ATP

Redox Reactions LEO the lion goes GER OIL RIG Loss of Electrons is Oxidation Oxidation Is Loss Gain of Electrons is Reduction Reduction Is Gain

 Oxidation: the loss of electrons from one substance  Reducing Agent: electron donor  Reduction: the gain of electrons to another substance  Oxidizing agent: electron acceptor; ex: oxygen

C 6 H 12 O 6 + 6O 2  6CO 2 + 6H 2 O + Energy As hydrogens are transferred to oxygen (and the status of electrons changes), energy is produced!!!

Molecules needed for Cell Respiration NAD + : coenzyme; an electron acceptor that functions as an oxidizing agent during respiration Dehydrogenase: enzymes that remove a pair of hydrogen atoms (2 electrons and 2 protons) from a substrate (thereby oxidizing it) and deliver 2 electrons and one proton to NAD+ creating NADH and H+ NADH: represents stored energy that can be trapped to make ATP when the electrons complete their “fall” down an energy gradient from NADH to Oxygen Electron transport chain: breaks the fall of electrons to oxygen into several energy-releasing steps instead of one explosive reaction; electrons are shuffled from one carrier molecule (usually protein) to another until the final electron acceptor - oxygen - accepts the electrons to make water

Molecules needed for Cell Respiration Electron’s “downhill” route:food  NADH  electron transport chain  oxygen e - --> food --> NADH --> etc --> oxygen

Difference between oxidative phosphorylation and substrate level phosphorylation WRITE DOWN!!!! Substrate-level phosphorylation- during Glycolysis & Kreb's Cycle. The physical addition of a free phosphate to ADP to form ATP. Substrate-level phosphorylation- during Glycolysis & Kreb's Cycle. The physical addition of a free phosphate to ADP to form ATP. Oxidative phosphorylation- takes place along the electron transport chain. ATP is synthesized indirectly via a proton gradient and movement of H+ protons back across the membrane through the protein channel, ATP synthase. Oxidative phosphorylation- takes place along the electron transport chain. ATP is synthesized indirectly via a proton gradient and movement of H+ protons back across the membrane through the protein channel, ATP synthase.

A Preview to Cellular Respiration Glycolysis: catabolic; occurs in the cytosol; Glycolysis: catabolic; occurs in the cytosol; Glucose  2 pyruvate substrate level phosphorylation

A Preview to Cellular Respiration Citric Acid Cycle: catabolic; occurs in mitochondrial matrix; completes the breakdown of glucose & gives off CO 2 substrate level phosphorylation Citric Acid Cycle: catabolic; occurs in mitochondrial matrix; completes the breakdown of glucose & gives off CO 2 substrate level phosphorylation

A Preview to Cellular Respiration Electron Transport Chain: accepts electrons, passes them along, and are accepted by oxygen to make ATP (oxidative phosphorylation) Electron Transport Chain: accepts electrons, passes them along, and are accepted by oxygen to make ATP (oxidative phosphorylation)

Glycolysis “ splitting of sugar ” Use 2 ATP for activation Glucose --> 2 Pyruvate 2 NADH 2 NADH 2 ATP (net) 2 ATP (net)

Intermediate Step Bridge between Glycolysis & Krebs

The Krebs/Citric Acid Cycle What goes in: 1 pyruvate, 4 NAD + 1 ADP + P, FAD What is produced: 3 CO 2, 4 NADH 1 ATP, FADH 2

Electron Transport Chain Electron Transport Chain: a collection of molecules (mostly proteins) embedded in the inner membrane of the mitochondrion; cytochomes are proteins in the electron transport chain; does NOT make ATP directly – only eases the ‘fall’ of electons Electron Transport Chain: a collection of molecules (mostly proteins) embedded in the inner membrane of the mitochondrion; cytochomes are proteins in the electron transport chain; does NOT make ATP directly – only eases the ‘fall’ of electons FADH adds its electrons farther ‘down stream’ so they do not create as much ATP FADH adds its electrons farther ‘down stream’ so they do not create as much ATP Oxygen is the final e- acceptor (WRITE DOWN) Oxygen is the final e- acceptor (WRITE DOWN)

Chemiosmosis: The Energy-Coupling Mechanism ATP Synthase: ATP Synthase: Enzyme that makes ATP from ADP and inorganic phosphate Chemiosmosis Chemiosmosis Process in which energy stored in the form of a hydrogen ion gradient across a membrane is used to drive ATP synthesis

Chemiosmosis: Energy Coupling e- go ALONG the membrane H + pump OUT THROUGH the membrane

ATP Production ENERGY FLOW Glucose --> NADH --> etc --> Proton Motive Force --> ATP

Fermentation

Fermentation Alcoholic Fermentation Alcoholic Fermentation Pyruvate  ethyl alcohol + 2 CO 2 Pyruvate  ethyl alcohol + 2 CO 2 carried out by many bacteria and yeast carried out by many bacteria and yeast ex: brewing, winemaking, baking ex: brewing, winemaking, baking Lactic Acid Fermentation Lactic Acid Fermentation Pyruvate  lactate Pyruvate  lactate carried out by many bacteria and fungus carried out by many bacteria and fungus ex: cheese, yogurt, muscles ex: cheese, yogurt, muscles

Fermentation: Cellular Respiration:

Evolutionary Significance of Glycolysis MOST WIDESPREAD METABOLIC PROCESS Ancient prokaryotes probably used glycolysis to make ATP long before oxygen was present in Earth’s atmosphere (cyanobacteria produced oxygen through photosynthesis later) ex: bacteria The location (in the cytosol) implies great antiquity  does NOT require a membrane-bound organelle

The Versatility of Catabolism Carbohydrates, fats, and proteins can all be used as fuel for cellular respiration. Carbohydrates, fats, and proteins can all be used as fuel for cellular respiration. Monomers of these molecules enter glycolysis or the citric acid cycle at various points. Monomers of these molecules enter glycolysis or the citric acid cycle at various points. Glycolysis and the citric acid cycle are catabolic funnels through which electrons from al kinds of organic molecules flow on their exergonic fall to oxygen. Glycolysis and the citric acid cycle are catabolic funnels through which electrons from al kinds of organic molecules flow on their exergonic fall to oxygen.

Biosynthesis (Anabolic Pathways) In addition to calories, food must also provide the carbon skeletons that cells require to make their own molecules In addition to calories, food must also provide the carbon skeletons that cells require to make their own molecules ex: intermediate or precursor molecules ex: intermediate or precursor molecules

Regulation of Cellular Respiration Allosteric enzymes(ones that need to have a conformational shape change) at certain points in the respiratory pathway respond to inhibitors and activators that help set the pace of glycolysis and the citric acid cycle. Allosteric enzymes(ones that need to have a conformational shape change) at certain points in the respiratory pathway respond to inhibitors and activators that help set the pace of glycolysis and the citric acid cycle.

Regulation of Cellular Respiration Phosphofructokinase, the enzyme that catalyzes step 3 of glycolysis, is an allosteric enzyme. It is stimulated by AMP (derived from ADP) but is inhibited by ATP and by citrate. Phosphofructokinase, the enzyme that catalyzes step 3 of glycolysis, is an allosteric enzyme. It is stimulated by AMP (derived from ADP) but is inhibited by ATP and by citrate.

Regulation of Cellular Respiration This feedback regulation adjusts the rate of respiration as the cell’s catabolic and anabolic demands change This feedback regulation adjusts the rate of respiration as the cell’s catabolic and anabolic demands change Ex. Low ATP increases cellular respiration; High ATP decreases C.R. and organic molecules are diverted for anabolic pathways. Ex. Low ATP increases cellular respiration; High ATP decreases C.R. and organic molecules are diverted for anabolic pathways.