Chapter 8: Cellular Respiration

I.  How cells acquire ATP

          A.  cellular respiration: step by step break down of food molecules for energy of ATP

          B.  aerobic respiration: used oxygen to breakdown glucose to CO₂ and H₂O

                    1.  oxidation: (loss of electrons) C₆H₁₂O₆ -> CO₂

                    2.  reduction: (gain of electrons) O₂ -> H₂O

                    3.  exergonic: C₆H₁₂O₆ + 6O₂ -> 6CO₂ + 6H₂O + energy

                    4.  endergonic: ADP + P + energy -> ATP

          C.  coenzyme NAD⁺ and FAD are carriers of electrons

                     1.  reduction: 2H⁺ + 2e^- + NAD -> NADH₂

                     2.  oxidation: NADH₂ -> NAD + 2H⁺ + 2e

          D.  metabolic pathways

                     1.  glycolysis: glucose (C₆) -> 2 pyruvate (C₃) + 2 ATP

                    2.  transition reaction: O₂ + pyruvate -> acetyl (C₂) + CO₂

                    3.  Krebs cycle: O₂ + acetyl -> CO₂ + 2 ATP

                    4.  electron transport system: carriers move electrons to make ATP

                    5.  fermentation: (no O₂) pyruvate -> alcohol + CO₂ + 2 ATP

II.  Outside the mitochondria (anaerobic)

          A.  glycolysis: in the cytoplasm, takes place in all cells, no O₂ needed

                    1.  2 P from 2 ATP activate glucose

                    2.  phosphorylation:

                              a.  ADP + P + energy <-> ATP

                              b.  ATP releases energy and P

                    3.  (coenzyme) NAD⁺ + H₂ -> NADH -> electron transport system

III.  inside the mitochondria (aerobic)

          A.  Mitochondria: double membrane system "powerhouse"

                     1.  cristae: folds of inner membrane, site of electron transport

                         system

                    2.  matrix: gel, site of transition reaction and Krebs cycle

          B.  aerobic respiration: goes through glycolysis first

                     1.  transition reaction: from glycolysis to Krebs cycle

                              a.  C₃ pyruvate -> acetyl group (C₂) + CO₂ + H₂O

                              b.  NAD⁺ + H₂ -> NADH -> electron transport system

                    2.  Krebs cycle or citric acid cycle

                              a.  acetyl-CoA -> 2 ATP + CO₂

                              b.  NAD⁺ + H₂ -> NADH -> electron transport system

                              c.  FAD + H₂ -> FADH -> electron transport system

                    3.  electron transport system:

                              a.  H⁺ picked up by coenzymes NAD and FAD

                              b.  chemiosmotic theory: movement of H⁺ across

                                   membranes to produce ATP

                              c.  gain of aerobic respiration: 36 ATP

10 NADH -> 28 ATP

2 FADH₂ -> 4 ATP

glycolysis -> 2 ATP

Krebs cycle-> 2 ATP

IV.  Metabolic pool: contains the parts to make molecules or energy as needed

          A.  catabolism: breaking down of molecules

                    1.  triglyceride -> glycerol + 3 fatty acids

                              a.  glycerol (C₃) -> PGAL -> pyruvate

                              b.  fatty acids -> acetyl -> Krebs cycle

                    2.  protein -> amino acids

                              a.  amino -> urea -> urine

                              b.  keto group -> pyruvate

          B.  anabolism: (synthesis) building up of molecules

                    1.  one molecule in the metabolic pool is converted to another

                    2.  too much carbohydrate is stored as fat

                              a.  PGAL -> glycerol

                              b.  acetyl -> fatty acids

                    3.  essential amino acids and fatty acids must be in the diet, can't

                           be synthesized

V.  fermentation: glycolysis first

          A.  alcoholic fermentation: glycolysis first, then

                    1.  glucose -> pyruvate -> alcohol + CO₂ + 2 ATP

                    2.  used for: brewing, baking

          B.  lactic acid fermentation: glycolysis first, then

                    1.  glucose -> pyruvate -> lactate + 2 ATP

                    2.  used in: making yogurt, sour cream, cheese, sauerkraut

                    3.  in O₂ starved muscles

                    4.  oxygen debt: O₂ + lactic acid -> pyruvate

          C.  advantages : rapid burst of ATP

          D.  disadvantages: low energy yield, toxicity