1.What happens to the CO2 and H2O produced during acetyl-CoA formation and the Krebs cycle? It is released to the environment (animals and plants). In plants, some of itmay be used in photosynthesis. 2. No matter what the source of energy might be, organisms must convert it to ___ ATP _______, a form of chemical energy that can drive metabolic reactions.3.Give the overall equation for the aerobic respiratory route; indicate where energy occurs in the equation. C 6 H 12 O 6 + 6O 2 ———> 6CO 2 + 6H 2 O + energy (energy from this reaction istransferred to ATP, but the majority is lost as heat). 4.In the first of the three stages of aerobic respiration, __ glucose ________ is partially degraded to pyruvate.5.Glycolysis occurs in the __ cytoplasm ________ of the cell.6.Explain the purpose served by molecules of ATP reacting first with glucose and then with fructose-6- phosphate in the early part of glycolysis (see Figure 7.4 in the text). The ATP is “priming the pump”. That is, it is supplying activation energyfor subsequent reactions. 7.Four ATP molecules are produced by __ substrate_-__level________ phosphorylation for everytwo used during glycolysis. Consult Figure 7.4 in the text.8.Glycolysis produces ___ 2_______ (number) NADH, ____ 2 ______ (number) ATP (net) and ____ 2______ (number) pyruvate molecules for each glucose molecule entering the reactions.9.Consult Figures 7.4 and 7.6 in the text. State the events that happen during the preparatory steps and explainhow the process of acetyl-CoA formation relates glycolysis to the Krebs cycle. Preparatory Steps and the Krebs Cycle1.Pyruvate enters the mitochondria and is converted toacetyl-CoA, which then joins oxaloacetate already presentfrom a previous “turn” of the cycle.2.During each turn of the cycle, three carbon atoms enter(as pyruvate) and three leave as three carbon dioxidemolecules.3. The pyruvate conversion to acetyl-CoA is the linkfrom gylcolysis to the Kreb’s cycle. 1
10.Explain, in general terms, the role of oxygen in aerobic respiration. Oxygen joins with the “spent” electrons and H+to yield water. 11.Consult Figure 7.5 in the text and predict what will happen to the NADH produced during acetyl-CoAformation and the Krebs cycle. This NADH enters the Electron Transfer Phosphorylation pathwaywere it will supply energy to support the chemo-osmotic production of ATP. 12.State which factors determine whether the pyruvate (pyruvic acid) produced at the end of glycolysis will enter into the alcoholic fermentation pathway, the lactate fermentation pathway, or the acetyl-CoA formation pathway. Alcoholic Fermentation (Oxygen not present)a.Fermentation begins with glucose degradation topyruvate.b.Cellular enzymes convert pyruvate to acetaldehyde,which then accepts electrons from NADH to becomealcohol.c.Yeasts are valuable in the baking industry (carbondioxide byproduct makes dough “rise”) and inalcoholic beverage production.Lactate Fermentation (Oxygen not present)a.Certain bacteria (as in milk) and muscle cells have theenzymes capable of converting pyruvate to lactate.b.No additional ATP beyond the net two from glycolysisis produced but NAD+is regenerated. . Acetyl-CoA Formation Pathway.a. If oxygen is present, then the pyruvate will enter thepreliminary steps pathway.b. Pyruvate will react with CoA enzyme to from acetyl CoA.This in turn hands off acetyl to oxaloacetic acid to become part of theKreb’s cycle. 2
