Biology

Course Number: 211G A20

Course Name: Online – Natural History of Life

Instructor: Catherine Hartkorn

Individual/Partner Project – Biology Math Problems Assignment

Remember to write out your calculations and explanations for ALL problems.

Problem Set 3 – Problems on Enzymes and Cellular Respiration (3 problems):

6. Hydrogen peroxide is usually stored in a brown bottle away from sunlight because it

spontaneously (but slowly) decomposes into O2 and water. In the brown bottle, the free

energy of activation ∆G + = 18 kcal/mol. In the presence of a catalyst, the decomposition

is much faster. For each decrease of 1.36 kcal/mol in ∆G + , the rate of reaction is ten

times faster.

In the presence of catalase, an enzyme found in the blood, ∆G + = 7 kcal/mol. In the

presence of the inorganic catalyst platinum, ∆G + = 13 kcal/mol.

a. How much faster is peroxide decomposition in the presence of a catalase?

b. How much faster is peroxide decomposition in the presence of platinum?

c. How many times faster is peroxide degradation under the influence of a catalase

than degradation under the influence of platinum?

7. You eat a candy bar that has 180 calories. This energy is converted during respiration to

ATP. The reaction ADP + Pi  ATP requires 7.3 kcal/mol. One “dietary” calorie is

equal to 1000 “chemical” calories. Respiration is maximally about 39% efficient in

converting substrate calories to ATP calories.

a. Assuming that all of the energy in the candy actually gets to the respiratory site

in the cell, how many ATPs could your body make from this candy bar?

8. The first two stages in respiration are glycolysis and Kreb’s cycle. For each molecule of

glucose input,

10 NAD + molecules are reduced

2 FADs are reduced

4 ADPs are phosphorylated.

The free energy ∆G 0 ’ of the relevant “respiration reactions” is:

Reaction ∆G 0 ’ (kcal/mol)

NADH + H + + ½ O2  NAD

+ + H2O -51.7

FADH2 + ½ O2 FAD + H2O -43.4

ATP  ADP + Pi -7.3

Glucose + 6 O2  6 CO2 + 6H2O -686

a. How much of the energy from one mole of glucose is converted into ATP during

the first two stages?

b. How much of the glucose energy is conserved in the reduced coenzymes NAD+

and FAD?

The third stage of respiration is oxidation phosphorylation.

c. A total of 32 ATPs per glucose molecule are made during oxidative

phosphorylation from the reduce coenzymes. How much of the glucose energy is

conserved in ATP at the end of ALL three stages?

d. What percentage of the total ATP energy is converted by the oxidative

phosphorylation of the reduced coenzymes?

e. What percentage of the glucose energy was lost was heat?

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