Prelim 3 Spr07 Key - 1. a. (1 point) Explain why ATP is...

Info iconThis preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon
1. a. (1 point) Explain why ATP is stable in water even though its standard free energy of hydrolysis is extremely favorable (-7.3 kcal/mol). (Nelson & Cox, p. 496) Although the free energy of hydrolysis is extremely favorable, the activation energy is large and so ATP is quite stable in water. Enzymes increase the rate of a reaction by stabilizing the transition state thereby reducing the energy of activation and allowing the favorable hydrolytic reaction to take place. b. (1 point) The standard oxidation-reduction potential for the reduction of O 2 to H 2 O is given as 0.82 V in Nelson & Cox. However, the value given in textbooks of chemistry is 1.23 V. Account for this difference. (Nelson & Cox, p. 510) Biochemists use E'°, the value at pH 7, whereas chemists use E°, the value in 1 M H + . The prime denotes that pH 7 is the standard state. 2. a. (3 points) Using structures , write a balanced equation for the net reaction catalyzed by glyceraldehyde 3-phosphate dehydrogenase. (You may use standard abbreviations for any cofactors or coenzymes.) (Nelson & Cox, step 6, p. 529) b. (1 point) In the reaction catalyzed by glyceraldehyde 3-phosphate dehydrogenase, a "high energy bond" is created. Where did the energy needed to create this bond come from? Oxidation - much of the free energy of oxidation of the aldehyde group of glyceraldehyde 3-phosphate is conserved by formation of the acyl phosphate group at C-1 of 1,3- bisphosphoglycerate. (1 point) Draw the structure of the high energy intermediate formed in the above reaction. You should have drawn the structure of the thioester intermediate shown in Fig. 14-7 on p. 530.
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
BioBM330 third Prelim ANSWERS 2 3. a. (2 points) Name the two overall processes that occur in the conversion of pyruvate to acetyl CoA. (not counting the addition of CoA.) (Nelson & Cox, pp. 602-6) 1) Decarboxylation 2) Oxidation b. (3 points) After a pair of electrons is removed from pyruvate, they are transferred through a series of cofactors in the pyruvate dehydrogenase complex. Name (in order) the three cofactors that successively accept these electrons. 1) Lipoyl lysine 2) FAD 3) NAD + c. (1 point) Does covalent modification increase or decrease the activity of the pyruvate dehydrogenase complex? (circle one) (Nelson & Cox, p. 621) decrease (1 point) Name the class of enzyme that adds the modifying group. Kinase (1 point) Name the class of enzyme that removes the modifying group. Phosphatase 4. (2 points) Name the branch of the pentose phosphate pathway that enables ribose 5-phosphate to be used to produce ATP? Explain briefly. Ribose 5-phosphate is converted to glyceraldehyde 3-phosphate using the reversible non-oxidative pathway. It can then enter the glycolytic pathway to generate reducing power and ATP.
Background image of page 2
BioBM330 third Prelim ANSWERS 3 5. a. (3 points) Using structures and including the intermediate , write in balanced form, the two reactions catalyzed by citrate synthase. (You
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 4
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 11

Prelim 3 Spr07 Key - 1. a. (1 point) Explain why ATP is...

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online