Ch8 Cellular Respiration Grabowski Notes PDF

**[Chapter 8 -- Grabowski Notes]** **8.1 Cellular Respiration** **1. Cellular respiration involves various metabolic pathways that break down carbohydrates and other metabolites with the concomitant buildup of ATP.** **2. Cellular respiration consumes oxygen and produces CO~2~; because oxygen is...

**[Chapter 8 -- Grabowski Notes]** **8.1 Cellular Respiration** **1. Cellular respiration involves various metabolic pathways that break down carbohydrates and other metabolites with the concomitant buildup of ATP.** **2. Cellular respiration consumes oxygen and produces CO~2~; because oxygen is required, cellular respiration is aerobic.** **3. Cellular respiration usually involves the complete breakdown of glucose into CO~2~ and H~2~O.** **4. The net equation for glucose breakdown is: C~6~H~12~O~6~ + 6 O~2~ = 6 CO~2~ + 6 H~2~O + energy** **5. Glucose is a high‑energy molecule; CO~2~ and H~2~O are low‑energy molecules; cellular respiration is thus *exergonic* because it releases energy.** **6. Electrons are removed from substrates and received by oxygen, which combines with H^+^ to become water.** **7. Glucose is oxidized and O~2~ is reduced.** **8. The reactions of cellular respiration allow energy in glucose to be released slowly; therefore ATP is produced gradually.** **9. In contrast, if glucose were broken down rapidly, most of its energy would be lost as non-usable heat.** **10. The breakdown of glucose yields synthesis of 36 or 38 ATP (depending on certain conditions); this preserves about 39% of the energy available in glucose.** **11. This is relatively efficient compared to, for example, the 25% efficiency of a car burning gasoline.** **A. NAD^+^ and FAD** **B. Phases of Cellular Respiration** **8.2 Outside the Mitochondria: Glycolysis** **1. Glycolysis occurs in the cytoplasm outside the mitochondria.** **2. Glycolysis is the breakdown of glucose into two pyruvate molecules.** **8.3 Fermentation** 1. **Fermentation is an *anaerobic* (i.e., occurs in the absence of oxygen) process which consists of glycolysis plus reduction of pyruvate to either lactate or to alcohol and CO~2~ (depending on the organism).** 2. **Animal cell fermentation results in lactate.** 3. **Bacteria can produce an organic acid like lactate, or an alcohol and CO~2~.** 4. **Yeasts produce ethyl alcohol and CO~2~.** 5. **NADH passes its electrons to pyruvate instead of to an electron transport chain; NAD^+^ is then free to return and pick up more electrons during earlier reactions of glycolysis.** **A. Advantages and Disadvantages of Fermentation** **2. Fermentation products are toxic to cells.** **B. Efficiency of Fermentation** **C. Fermentation Helps Produce Numerous Food Products (*Science Focus box*)** **1. Yeast Fermentation** **2. Bacterial Fermentation** **3. Soy Sauce Production** **8.4 Inside the Mitochondria** **1. The next reactions of cellular respiration involve the preparatory reaction, the citric acid cycle, and the electron transport chain.** **2. These reactions occur in the mitochondria.** **3. A mitochondrion has a double membrane with an intermembrane space (between the outer and inner membrane).** **4. *Cristae* are the inner folds of membrane that jut into the *matrix*, the innermost compartment of a mitochondrion that is filled with a gel‑like fluid.** **5. The prep reaction and citric acid cycle enzymes are in the matrix; the electron transport chain is in the cristae.** **6. Most of the ATP produced in cellular respiration is produced in the mitochondria; therefore, mitochondria are often called the "powerhouses" of the cell.** **A. Preparatory Reaction** **B. Citric Acid Cycle** 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. a. **The six carbon atoms in the glucose molecule have now become the carbon atoms of six CO~2~ molecules, two from the prep reaction and four from the citric acid cycle.** **C. The Electron Transport Chain** **2. NADH and FADH~2~ carry the electrons to the electron transport system.** **3. Members of the Chain** **4. Cycling of Carriers** **a. By the time electrons are received by O~2~, *three* ATP have been made.** **b. When FADH~2~ delivers electrons to the electron transport system*, two* ATP are formed by the time the electrons are received by O~2~.** **5. The Cristae of a Mitochondrion and Chemiosmosis** **D. Energy Yield From Glucose Metabolism** **2. ETC and Chemiosmosis** **3. Efficiency of Cellular Respiration** **8.5 Metabolic Pool** **1. In a metabolic pool, substrates serve as entry points for degeneration or synthesis of larger molecules.** **2. Degradative reactions (catabolism) break down molecules; they tend to be exergonic.** **3. Synthetic reactions (anabolism) build molecules; they tend to be endergonic.** **A. Catabolism** **1. Just as glucose is broken down in cellular respiration, other molecules in the cell undergo catabolism.** **2. Fat breaks down into glycerol and three fatty acids.** **a. Glycerol is converted to G3P, a metabolite in glycolysis.** **b. An 18‑carbon fatty acid is converted to nine acetyl‑CoA molecules that enter the citric acid cycle.** **c. Respiration of fat products can produce 108 kcal in ATP molecules; fats are an efficient form of stored energy.** **3. Amino acids break down into carbon chains and amino groups.** **a. Hydrolysis of proteins results in amino acids.** **b. *R*‑group size determines whether carbon chain is oxidized in glycolysis or the citric acid cycle.** **c. A carbon skeleton is produced in the liver by removal of the amino group, by the process of deamination.** **d. The amino group becomes ammonia (NH~3~), which enters the urea cycle and ultimately becomes part of excreted urea.** **e. The size of the *R*‑group determines the number of carbons left after deamination.** **B. Anabolism** **1. ATP produced during catabolism drives anabolism.** **2. Substrates making up pathways can be used as starting materials for synthetic reactions.** **3. The molecules used for biosynthesis constitute the cell's metabolic pool.** **4. Carbohydrates can result in fat synthesis: G3P converts to glycerol, acetyl groups join to form fatty acids.** **5. Some metabolites can be converted to amino acids by *transamination*, the transfer of an amino acid group to an organic acid.** **6. Plants synthesize all the amino acids they need; animals lack some enzymes needed to make some amino acids.** **7. Humans synthesize 11 of 20 amino acids; the remaining 9 essential amino acids must be provided by the diet.** **C. The Energy Organelles Revisited** **1. Chloroplasts and mitochondria may be related based on their likeness, yet they carry out opposite processes.** **a. The inner membrane of the chloroplasts form the thylakoids of the grana. The inner membrane of the mitochondrion forms the convoluted cristae.** **b. In chloroplasts the electrons passed down the ETC have been energized by the sun. In mitochondria the electrons passed down the ETC have been removed from glucose products.** **c. In chloroplasts the stroma contains the enzymes of the Calvin cycle. In the mitochondria the matrix contains the enzymes of the citric acid cycle.** **2. Flow Of Energy** **a. Energy flows through organisms. For example, the sun is the energy source for producing carbohydrates in chloroplasts. In the mitochondria, the carbohydrate energy is converted into ATP molecules during cellular respiration.** **b. Chemicals cycle throughout cells. Mitochondria use carbohydrates and oxygen produced in chloroplasts, and chloroplasts use carbon dioxide and water produced in the mitochondria.**