BCH 451 Spring 2008                                   Exam #4 

1.         (3) Write the net balanced equation for A = glycolysis; B = gluconeogenesis; C = Citric Acid Cycle:

2.         (4) For step of glycolysis, name the enzyme, give the class of the enzyme, draw the structures of the non-cofactor substrate(s) and product(s) connected by the reaction arrows, which show the reversibility or irreversibility, show the co-substrates coming in and out of the reaction as appropriate using the usual abbreviations, and list all other cofactors under the reaction arrow(s):

Enzyme name:                                    Enzyme class:

Reaction:

3.         (4) For step of the Krebs cycle, name the enzyme, give the class of the enzyme, draw the structures of the non-cofactor substrate(s) and product(s) connected by the reaction arrows, which show the reversibility or irreversibility, show the co-substrates coming in and out of the reaction as appropriate using the usual abbreviations, and list all other cofactors under the reaction arrow(s):

Enzyme name:                                    Enzyme class:

Reaction:

4.         For complex in oxidative phosphorylation,:

(0.3)    full and complete name of the complex:

(0.2)    number of protons which enter the complex from the matrix:

(0.2)    number of protons pumped out of the complex into the inner membrane space:

(0.4)    substrates and/or co-substrates [full names and not abbreviations; no structures]:

(0.4)    products and/or “co-products” [full names and not abbreviations; no structures]:

(0.6)    non co-substrate cofactors and/or prosthetic groups:

5.         (2) PUZZLER Next week, we will learn how fatty acids are broken down into multiple acetyl-CoA molecules using the β-oxidation cycle in the matrix. In these process, many molecules of NADH and QH₂ are also produced. A cell which has access to both glucose and fatty acids will preferentially utilize the fatty acids as a source of energy. Propose an explanation of this preference.

6.         Compare and contrast the glycerol-3-phosphate shunt and the malate-aspartate shuttle:

            a.         (1) Define shuttle:

            b.         (0.4 each) What enzymes are in each shuttle?

            c.         (1.5) Why are cytosolic and mitochondrial forms of the same enzyme called isozymes?

            d.         (1) What is the purpose of these two shuttles?

            e.         (1) Where are they located?

            f.         (2.5) How are they different from each other than part b? [continue on back of page 3 as necessary]

7.         Uncouplers

            a.         (1) Define uncouplers:

            b.         (0.5) Draw the structure of 2,4-dinitrophenol:

            c.         (1) From your knowledge of organic chemistry, what are the nitro groups doing to this molecule other than making it yellow in color?

            d.         (1) What does 2,4-dinitrophenol uncouple?

            e.         (2) Based on your comments in part c, why does 2,4-dinitrophenol act as an uncoupler?

8.         (0.3 each) Fill in the blanks:

Enzyme #3 in glycolysis

Enzyme in gluconeogenesis which replaces the previous enzyme [#3 in glycolysis]

Regulators and their effects on the previous enzyme in gluconeogenesis

Regulator and its effects on enzyme #4 in the TCA cycle

Energy of a thioester as compared with ATP

Energy of cAMP as compared with ATP

Regulators and their effects on enzyme #3 in glycolysis

Relationship between free energy and EMF

Where in the cell is pyruvate carboxylase located

The total number of ATP molecules synthesized per the complete oxidation of pyruvate

Mannose uses these two enzymes to enter glycolysis

These two enzymes are found in the bisphospho-glycerate shunt