Anaerobic Cellular Respiration No () available Only produces the amount of ATP generated by glycolysis() Converts excess that cannot be processed in the Krebs cycle to or Fermentation – pathway taken by pyruvate to produce ATP in anaerobic conditions Two types: Lactate Fermentation Ethanol Fermentation

Lactate Fermentation Occurs in the Occurs when energy demands oxygen supply Cells convert molecules into lactate or Use as energy source Lactate is stored When oxygen levels increase lactate is converted back to pyruvate Pyruvate proceeds to Krebs cycle

Ethanol Fermentation Anaerobic process Occurs in the of cells Process in which and some convert to and CO 2 Used to produce alcoholic beverages and aid in the rising of bread

4 Anaerobic Respiration Both types of fermentation use energy and free to accept supplying a small amount of energy and preventing the cell from becoming acidic Various other chemical pathways exist which allow some organisms to thrive in anoxic and hypoxic conditions

Summary

Cellular Respiration Releases Energy from Organic Compounds - Review Three metabolic pathways make up aerobic cellular respiration. A. B. C.

Cellular Respiration Releases Energy from Organic Compounds - Review The first set of reactions in aerobic cellular respiration is called. It is an process. During glycolysis, a small amount of ATP is generated, and NAD + is reduced to NADH.

8 Stage 1 of Glycolysis Glucose ↓ (ATP -> ADP) [phosphorylation] glucose phosphate ↓ [rearranged] fructose phosphate ↓ (ATP -> ADP) [phosphorylation] fructose diphosphate ↓ [split] PGAL  PGAL a.a. b. c. d.

9 Stage 2 Glycolysis PGAL ↓NAD -> NADH PGA ↓ADP -> ATP PGA ↓ADP -> ATP Pyruvate a. b. c.

Cellular Respiration Releases Energy from Organic Compounds - Review The fate of pyruvate, the final product of glycolysis, depends on the availability of oxygen (anerobic and aerobic) and on the type of organism. When is available, enters the of the mitochondrion. A series of reactions yield carbon dioxide() and. NAD + is to NADH. Transition Reaction

Cellular Respiration Releases Energy from Organic Compounds - Review Acetyl-CoA enters the Krebs cycle by combining with a four-carbon compound  During the Krebs cycle, two carbon atoms are fully oxidized to carbon dioxide, NAD + and FAD are reduced to and, and a small amount of ATP is produced.() citrate

Cellular Respiration Releases Energy from Organic Compounds - Review The NADH and FADH 2 from the Krebs cycle their electrons to the electron carriers() in the electron transport chain. As electrons are passed from one carrier to the next, the energy that is released is used to pump hydrogen ions() across the mitochondrial inner membrane into the intermembrane space, creating a concentration gradient. The energy stored in the gradient is used to generate ATP by chemiosmosis.

Cellular Respiration Releases Energy from Organic Compounds - Review Organisms that carry out anaerobic cellular respiration use inorganic chemicals other than oxygen as the final electron-acceptor. This produces ATP for the cell, but not as much as in aerobic respiration. breakdown of glucose in the presence of oxygen 36 ATP breakdown of glucose by lactate or ethanol fermentation 2 ATP

Cellular Respiration Releases Energy from Organic Compounds - Review In muscle that is functioning anaerobically, pyruvate is converted to lactate and the reduced NADH is reoxidized so that glycolysis can continue. This process is called lactate fermentation.

Cellular Respiration Releases Energy from Organic Compounds - Review In yeast growing anaerobically, pyruvate is converted to carbon dioxide and ethanol. This process is known as ethanol fermentation.

Cellular Respiration Releases Energy from Organic Compounds - Review Fermentation is used on an industrial scale to produce ethanol. Ethanol is used as an additive to gasoline to reduce some environmental contaminants. Selected Fermentation Products and their Uses

Chapter Concept Organizer

Chapter Summary P/S and C/R proceed through many different rxns to produce energy-rich compounds and break them down to release their stored energy (ATP) When the bond to the last phosphate group is broken, leaving ADP and a free phosphate group, the energy released is available to do cellular work. In P/S the CO 2 and H 2 O are involved in two separate sets of reactions: H 2 O is split into hydrogen ions, electrons, and oxygen in the light- dependent reactions CO 2 is incorporated into carbohydrates in the light-independent reactions.

Chapter Summary (cont’d) light-dependent rxns (thylakoid membranes) capture light energy and use it to excite electrons to produce ATP and NADPH. light-independent reactions (stroma) use the chemical potential energy of ATP and the reducing power of NADPH to reduce carbon dioxide and form glucose via the Calvin- Benson cycle. Glucose is processed to release energy through glycolysis, the Krebs cycle, and electron transport Glycolysis is an anaerobic process that occurs in the cytoplasm and breaks down glucose into pyruvate Pyruvate enters the mitochondria, where it is broken down into carbon dioxide and acetyl CoA.

Chapter Summary (cont’d) Acetyl CoA enters the Krebs cycle (matrix) and energy released from breakdown of compounds in the Krebs cycle is used to reduce NAD -> NADH and FAD -> FADH NADH & FADH donate electrons to the ETC on the inner mitochondrial membranes Energy, released as electrons, is passed along the chain & used to create a hydrogen ion gradient that powers chemiosmosis, which generates ATP. Glycolysis is the only source of energy for some organisms. Pyruvate is broken down into carbon dioxide and alcohol (ethanol fermentation) or lactate (lactate fermentation). This process occurs anaerobically.

Chapter Review What molecule provides energy for most cellular processes? Would photosynthesis and respiration be able to proceed without enzymes? Why or why not? Where are chlorophyll molecules found? What happens when a compound is oxidized? Reduced? Which form contains more energy? What occurs during chemiosmosis? Where does it occur? What metabolic pathways are involved in cellular respiration? Where do they occur?