Question

Name: 4. Put the following reactions in the order they occur in elycolysis. Indicate reactions do not occur (exactly in reverse) in the gluconeogenic pathway and also which steps are likely to be catalyzed by a highly regulated enzyme. Also indicate which step would "back up" under anaerobic conditions if fermentation did not occur (16 pts) (a) Dehydration of 2-Phosphoglycerate to form PEP (b) Phosphorylation of Fructose-6-Phosphate to form Fructose-1,6-bis- Phosphate (c) 1,3-Phosphoglycerate reacts with ADP to generate ATP (d) Phosphorylation of Glucose to form Glucose-6-Phosphate (e) Reaction of NAD, Glyceraldehyde-3-Phosphate and inorganic phosphate to yield 1,3-Phosphoglycerate and NADH 5. Identify in the following structure: (A) a readily broken (e.g. via an aldol cleavage or similar reaction) C-C bond, (8) a hydroxyl group that can be epimerized via an enediol intermediate, (C) a hydroxyl group that would likely be epimerized via reversible oxidation to a ketone, (D) a C-C bond that can be broken using thiamine as a cofactor, (E) a leaving group that could facilitate formation of an ether (2 pts each) HO ?? ?? (image accessed from the Wikipedia Commons, 7 May 2017)

Answer 1

4] The sequence of reactions will be in the following order---

[d] Phosphorylation of glucose to form glucose -6-phosphate.

The glucose ring is phosphorylated i.e. a phosphate group is derived from ATP and added to glucose . Thus , one molecule of ATP is consumed .

   [b] Phosphorylation of fructose -6- phosphate to form 1,6 fructose biphosphate

   One molecule of phosphate is derived from ATP and added to fructose -6- phosphate to convert it into 1,6-fructose biphosphate. Thus, one more molecule of ATP is consumed.

  [e] Reaction od NAD+ , glyceraldehyde -3-phosphate and inorganic phosphate to yield 1,3- phosphoglycerate and NADH.

Glyceraldehyde-3-phosphate is oxidised by the coenzyme NAD . The molecule is phosphorylated by the addition of a free phosphate group.

[c] 1,3- phosphoglycerate reacts with ADP to generate ATP

In this step , 1,3 biphosphoglycerate is converted to 3-phosphoglycerate by the enzyme phosphoglycerate kinase. A phosphate group is transferred to a molecule of ADP yielding the first molecule of ATP. Since there are two molecules biphosphoglycerate, we get two molecules of ATP.

[a] Dehydration of phosphoglycerate to form PEP

   In this step, the enzyme enolase removes a molecule of water from 2-phosphoglycerate to form phosphoenol pyruvic acid [PEP] .

6]   B-helix -- [c] protein secondary structure consisting of parallel and anti-parallel extended strands connected by inter strand hydrogen bonds . Similar structures occur in cellulose fibers.

B-sheet -- [e] double helical structure of DNA in fibers prepared under hydrating conditions

  Lipid -bilayer --[b] structures formed by 'rod-shaped' amphiphathic lipids placed in aquous solution .The ability of lipids to form this structure is critical to the form and function of the cell membrane.

Pyranose -- [a] cyclic hemiacetal or hemiketal with a six carbon ring.

Allosteric site - [f] location on an enzyme's surface away from the active site where a regulatory compound or even the substrate binds that enzyme.

  Active site --[d] location of an enzyme where catalysis occurs.