Bioenergetics & Kinetics

Question 1

Define entropy

Answer 1

The degree of disorder in a system; ΔS = + in a favorable reaction

Question 2

Define enthalpy

Answer 2

Pertains to the total heat content of the system (i.e. internal energy); ΔH = - in a favorable reaction (exothermic; heat is released)

Question 3

Define free energy

Answer 3

Gibb’s free energy measures the favorability/usefulness of a reaction. ΔG = ΔH – TΔS. –ΔG = a favorable reaction that occurs spontaneously.

Question 4

Define high-energy compounds

Answer 4

High-energy compounds generally contain thioester bonds or high-energy phosphate bonds. Energy is released by hydrolysis of high-energy bonds.

Question 5

Define oxidation-reduction reactions

Answer 5

Involves an exchange of electrons. To be reduced is to gain electrons. Measured by reduction potential E, a measure of readiness of molecule to accept electrons. +E = readily accepts (favorable reactions have +E). –E = readily donates. ΔG = -nFΔE.

Question 6

Define First Law of Thermodynamics

Answer 6

Energy can neither be created nor destroyed; it just changes form.

Question 7

Define Second Law of Thermodynamics

Answer 7

The entropy of the universe is always increasing.

Question 8

What are different forms of energy?

Answer 8

Kinetic (thermal, radiant, mechanical, electric) & Potential (stored in chemical bonds, concentration gradients, electric fields, and redox pairs)

Question 9

What are ‘standard conditions?’

Answer 9

1atm, 298K, 1mmol Mg, aqueous environment, pH 7

Question 10

What is the sign of standard free energy in a favorable reaction under standard conditions?

Answer 10

Negative

Question 11

What are the major high-energy compounds used in biological systems?

Answer 11

ATP, acetyl CoA, phosphocreatine, phosphoenolpyruvate

Question 12

What is the difference between coenzymes and cofactors?

Answer 12

Coenzymes are used up in an enzymatic reaction, while cofactors are not.

Question 13

A coenzyme or cofactor tightly bound to an enzyme is called a ____________. The resulting complex is called a ____________. The protein in isolation is called a _____________.

Answer 13

Prosthetic group. Holoenzyme. Apoenzyme.

Question 14

Are enzymes optimized to bind the substrate, transition state, or product?

Answer 14

Transition state

Question 15

In the Michaelis-Menten equation, what is Km?

Answer 15

The substrate concentration at which enzyme velocity is half the maximal

Question 16

In the Michaelis-Menten equation, what is Kcat?

Answer 16

The number of substrate molecules turned over into product per enzyme per second (aka how quickly the enzyme works)

Question 17

What does the value of kcat/km indicate about the efficiency of an enzyme?

Answer 17

The higher the value, the more efficient the enzyme

Question 18

What kind of enzyme usually recognizes palindromic DNA sequences?

Answer 18

Restriction enzyme

Question 19

Gel electrophoresis separates DNA on the basis of what characteristic?

Answer 19

Size

Question 20

SDS-PAGE separates proteins on which basis?

Answer 20

Size