13. Which statement is true about cellular respiration? You cannot obtain energy

Question

13. Which statement is true about cellular respiration? You cannot obtain energy (ATP) from protein because of the energy expenditure You can obtain energy from both proteins and fat even though the initial energy expenditure is much A, B, and C are all true statements Neither A, B nor C is correct statement B) C) D) E) 14. Adenosine Triphosphate (ATP) is a transformed form of sun's energy fueling cellular work A) This statement is false as ATP is not ultimately derived from sun B) This statement is true as all energy form in our solar system is derived from sun C) ATP is generated from carbohydrates and the sun has nothing to do with it. D) I am a little confused by this question and answer choices The breaking apart of water in photosynthesis is critical to animals because it produces what 15. A) Generates ATP B) Regenerates RuBP. C) Creates a food source. D) Consumes carbon dioxide. E) Oxygen. 16. When glucose is the fuel source, what is the correct sequence of stages in cellular respiration? A) Krebs cycle, electron transport, glycolysis B) Electron transport, Krebs cycle, glycolysis C) Krebs cycle, glycolysis, electron transport D) Electron transport, glycolysis, Krebs cycle E) Glycolysis, Krebs cycle, electron transport

Explanation / Answer

13. Correct statement is C , both protein and fats can generate energy even though initial energy expenditure is much. Proteins are first broken down to amino acids. Proteosome hydrolyze the peptide bonds using ATP. Therefore the initial energy expenditure is much. Later on amino group of amino acids is removed to form alpha keto acids( carbon skeletons) and ammonia. carbon skeletons can be dregarded to acteyl CoA , pyruvate, alpha-ketoglutarate, succinyl-CoA, fumarate, oxaloacetate and aceto-acetyl CoA. The kreb cycle intermediates can be broken down via kreb cycle and give NADH and FADH2.   This  NADH and FADH2 can be used in electron transport chain to generate ATP ( energy). The kreb cycle intermediates ca be converted to glucose via gluconeogenesis and the newly sythesized glucose can be undergo glycolysis to generate ATP .

Fats can produce a large amount of energy. Fatty acid palmitic acid can generate 106 ATP via its oxidation. During oxidation of fats NADH, FADH2 and acteyl CoA  is generated. Acteyl CoA channels into kreb cycle and  NADH, FADH2 enter electron transport chain. But before fatty acid oxidation begins, each molecule has to be activated in a ATP dependet reaction to form fatty acyl CoA. The reactionis catalyzed by acyl CoA ligase. Therefore the initially energy is required to activate fatty acids.

14. correct statement is B , all energy in our solar system is derived from sun. Carbohydrates are synthesized by plants and plants use light energy to synthesize ATP and precursor for carbohydrate synthesis . For example: Glucose is synthesized via calvin cycle. A major metabolite required for functioning of this cycle is NADPH. This NADPH molecule is synthesized during cyclic photophosphorylation reaction. In cyclic photophosphorylation, photosystems ( containing chlorophyll and other accessory pigments) absorb light energy of different wavelengths (700 and 680 nm) . Using this light energy an electron is ejected from the special pair of chlorophyll. This electron then moves across gradient via different carrier ultimately reducing NADP+ to NADPH. The transfer of light energy takes place via electron to NADPH and ultimately to glucose molecule. Also during electron movement, proton motive force is generated which is used to make ATP. Thus light energy is ulitmately giving rise to ATP and glucose. Glucose is used by humans and other animals to generate ATP during glycolysis. Therefore we can say that sun is fuelling cellular work.

15. E oxygen. Splitting of H2O produces oxygen during photophosphorylation. Oxygen evolving complex breaks down water molecule. Electron released are given to oxidized chlorophyll molecule of photosystem II. Thus reduced chlorophyll is regenerated.

16. E glycolysis, kreb cycle , electron transport. Glucose is first broken down to pyruvate and energy released is stored in ATP and NADH molecules. Pyruvate is then oxidized to actely CoA . acteyl CoA enters krebs cycle to get further oxidized. Energy released is stored in NADH and FADH2. Electrons from NADH and FADH2 enter the electron transport chain to synthesize ATP.

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