7. Why is the doorway step needed to link glycolysis and the Krebs Cycle?

Glycolysis takes place inside the cytoplasm. Mitochondria is the site for kreb's cycle. Since both…

Answered: 7. Why is the doorway step needed to…

Biochemistry

9th Edition

ISBN:9781319114671

Author:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.

Publisher:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.

Chapter1: Biochemistry: An Evolving Science

Section: Chapter Questions

Problem 1P

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4. The urea cycle was the first metabolic cycle to be discovered, predating the description of the citric acid cycle by 5 years. Hans Krebs along with Kurt Henseleit used their Warburg manometer (pictured) to monitor the use of carbon dioxide and ammonia in the synthesis of urea. In the presence of a slice of liver, urea could be produced, but the reaction require ornithine and citrulline. Since citrulline is not consumed during the course of the enzymatic cycle, but is rather regenerated, Krebs described 2N citrulline as a "catalyst" of the process. ОН ÑH2 (a) What do initiation of the urea cycle and initiation of gluconeogenesis have in common? What is the first committed step of the urea cycle, what reactants are used, what product is (b) produced, where does it take place, how is it allosterically regulated, and how is the allosteric regulator produced?
2. What is the chemical reaction that lactase catalyzes? Write it below in word form as well as in its chemical equation.
1. With what molecule does the acetyl group entering the Kreb’s Cycle join? 2. What is the first intermediate compound in the Kreb’s Cycle?
5. The keto acids of the TCA cycle are also the other substrates of the aminotransferase family. How does this family of enzymes play a role in maintaining the NAD re-oxidation of NADH to NAD during glycolysis? (Use the amino acids alanine, aspartate, and glutamate in your explanation)
12.
11.Discuss three mechanisms through which lactate can be used as an energy source.
15. The second high energy intermediate metabolite of glycolysis that can be used for substrate level phosphorylation is also a precursor molecule for the synthesis of several amino acids. Name 5 of these amino acids.
28. Sucrose in human nutrition is hydrolyzed into its monosaccharide components by sucrase. Glucose can enter directly in cellular respiration while fructose is predominantly metabolized in the liver as illustrated in the figure below. Suppose 180 molecules of sucrose are to be catabolized, what is the net ATP production during glycolysis considering both substrate-level phosphorylation and oxidative phosphorylation of NADH shuttled by malate and aspartate to the mitochondrion? [Hint: Sum of net ATP yield in substrate-level phosphorylation and ATP from glycolytic NADH] Fructose Glucose Glycogen ATP- ATP- ADP4 ADP+ hexokinase glucokinase Glucose-6-P→→→→→ Glucose-1-P Fructose-6-P Fructose-1,6-BP fructokinase rapid Fructose-1-P Rate aldolase B limiting Dihydroxyacetone-P Glyceraldehyde ATP- triose kinase ADP Glyceraldehyde-3-P Liver Also intestinal cells and kidney cortex O a. 810 ATP O b. 1260 ATP O c. 1800 ATP d. 2520 ATP PFK-1 Dihydroxy- acetone-P Lactate F1,6bisphosphatase…
2. A person performs intense exercise (for example, runs away from danger) 30 minutes after a carbohydrate-rich lunch. Why does the glycogen synthesis stop in skeletal muscles in this situation? Why is glycogen breakdown stimulated? To answer the questions: a) write a diagram of glycogen synthesis, specify the reactions associated with energy consumption when a glucose molecule is included in a growing glycogen chain; b) write the glycogen mobilization diagram and calculate the ATP amount that can be produced if glucose 1-phosphate is further oxidized to CO, and H,O in the muscles; c) indicate the hormone with an increased level in blood under stress situations, and how this hormone affects the activity of regulatory enzymes of glycogen synthesis and breakdown.
D3
6) What are the biological functions of the pentose phosphate pathway? What are the two stages and what is the purpose of each? What are the key enzymes for transferring carbons and how do each work?
1. Diagram the connection of the following pathways: glycolysis, gluconeogenesis, pentose phosphate pathway, glycogen synthesis, glycogen synthesis, glycogen degradation. Use key intermediate names, pathway names and arrows in your diagram.

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