Chapter 10 Exam III

Question 1

What are the three major types of work that cells carry out?

Answer 1

1. chemical work: synthesis of complex molecules.
2. transport work: take up nutrients, eliminate wastes and maintain ion balances.
3. mechanical work: cell motility and the movement of structures within cells.

Question 2

What is energy?

Answer 2

the capacity to do work or to cause particular changes.

Question 3

What is the first law of thermodynamics?

Answer 3

energy can neither be created nor destroyed.
the total energy in the universe remains constant.
energy may be redistributed either within a system or between the system and its surroundings.

Question 4

What is the second law of thermodynamics?

Answer 4

physical and chemical processes proceed in such a way that the disorder of the universe (entropy) increases to the maximum possible.
energy is measured in calories where 1 calorie is the amount of head energy needed to raise the temperature of 1 gram of water one degree celcius.

Question 5

How many joules are in one calorie?

Answer 5

4.2 joules.

Question 6

What is free energy?

Answer 6

the changes in energy that occur during chemical reactions.

Question 7

What is the free energy change?

Answer 7

the amount of energy in a system available to do work.

Question 8

What is the free energy change directly related to?

Answer 8

the equilibrium constant of the reaction.

Question 9

What is the standard free energy change?

Answer 9

the change in free energy under standard conditions of concentration, pH, pressure, and temperature.

Question 10

What if dG is negative?

Answer 10

the equilibrium constant is greater than one and the reaction goes to the right.
the reaction is said to be exergonic.

Question 11

What if dG is positive?

Answer 11

the equilibrium constant is less than one and little product will be formed at equilibrium.
endergonic.

Question 12

What are metabolites?

Answer 12

the products of reactions.

Question 13

What is metabolite flux?

Answer 13

the rate of turnover of a metabolite.

Question 14

What is a holoenzyme?

Answer 14

an enzyme consisting of a protein component (apoenzyme) and a nonprotein component (cofactor).

Question 15

What is a prosthetic group?

Answer 15

a cofactor that is firmly attached to the apoenzyme.

Question 16

what is a coenzyme?

Answer 16

a cofactor that is loosely attached to the apoenzyme; may dissociate from the apoenzyme and carry one or more of the products of the reaction to another enzyme.

Question 17

What is the Michaelis constant?

Answer 17

the substrate concentration required fro th ereaction to reach half maximal velocity; it is used as a measure for the apparent affinity of an enzyme for its substrate.

Question 18

What factors affect enzyme activity?

Answer 18

alterations in pH and temperature.

Question 19

why is regulation of metabolism essential?

Answer 19

for microorganisms to conserve energy and material and to maintain metabolic balance despite frequent changes in their environment.

Question 20

What are the three ways that metabolic processes can be regulated?

Answer 20

1. metabolic channeling: the localization of metabolites and enzymes in different parts of a cell.
2. Increasing or decreasing the number of enzyme molecules present (regulation of gene expression)
3. stimulation or inhibition of critical enzymes in a pathway (posttranslational regulation).

Question 21

Describe metabolic channeling.

Answer 21

1. compartmentation is a common mechanism. enzymes and metabolites are distributed in separate cell structures or organelles.
2. channeling can occur within a compartment.
3. channeling can generate marked variation in metabolite concentrations and therefore directly affect enzyme activity.