1. Which of the following stages in the breakdown of the piece of toast you had
ID: 61217 • Letter: 1
Question
1. Which of the following stages in the breakdown of the piece of toast you had for breakfast generates the most ATP?
- the digestion of starch to glucose
- glycolysis
- the citric acid cycle
- oxidative phosphorylation
1b. Explain your answer above, citing ATP numbers for each stage.
1c. If you weigh yourself on a scale one morning, then eat four pounds of food during the day, will you weigh four pounds more the next morning? Why or why not? (Hint: Your biomass consists of carbohydrates, fats, and proteins, all carbon-based molecules that can be broken down into the molecule acetyl CoA. This molecule enters the citric acid cycle and is broken down further to extract energy).
Explanation / Answer
1. a. Oxidative phosphorylation produces the heigest amount of ATP (about 24 to 36 ATP's per one glucose molecule).
b.
- the digestion of starch to glucose -----------> Do not produce ATP's (It is a digestion process, not metabolism)
- glycolysis -------------------------------------------->Generates 2 molecules of ATP
- the citric acid cycle ------------------------------> Generates 1 ATP molecule as a direct source of energy
- oxidative phosphorylation ------------------------> Generates 26 to 34 ATP molecules approximately
Glycolysis is an anaerobic process, through which one glucose molecules is breakdown into two molecules of three carbon pyruvate. The glycolysis of each glucose molecule generates 2 ATP molecules.
The pyruvate generated by the glycolysis is converted into acetyl-CoA that enters into the citric acid cycle. Citric acid cycle involves a series of reactions that occur in the presence of oxygen. Citric acid cycle generates NADH, which enters into the oxidative phosphorylation process. This cycle occurs in mitochondrial matrix; it consumes 2 water molecules, and generagenerates two carbondioxide molecules along with one ATP molecule as a direct energy source.
“Oxidative phosphorylation” is an aerobic process that involves a series of reactions, which include the transfer of electrons from the NADH or FADH2 to oxygen. This process involves the transfer of electrons (oxidation) by a series of electron carriers (electron transport system (ETS)) and attachment of phosphate group (phosphorylation). Pyruvate by oxidative phosphorylation gains 34 ATP molecules from each pair (each pyruvate generates 17 ATP molecules), this is an aerobic process.
The free energy released by oxidative phosphorylation contributes to the major part (nearly above 90%) of energy expenditure of our daily activities
c). No, the weight will not increase by four pounds in the next morning. This is because, the food what we eat is digested and the nutrients are metabolized to derive energy. Some of the energy is utilized for daily activities, and excess energy is stored. The unabsorbed food is excreted.
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