Energetics

Question 1

What is the first law of thermodynamics

Answer 1

-Energy cannot be created or destroyed, only transformed

Question 2

What is Enthalpy?

Answer 2

Total heat absorbed by a system assuming constant pressure (only in bio). Change in enthalpy is delta H

Question 3

What is the enthalpy of a exothermic reaction and why?

Answer 3

Negative, because it releases heat.

Question 4

What is the enthalpy of an endothermic reaction and why?

Answer 4

Positive, because it absorbs heat

Question 5

What kinds of ‘work’ are carried out in biological systems?

Answer 5

• Mechanical; by muscles
• Electrical; by nerves
• Chemical; in molecule synthesis

Question 6

What is the second law of thermodynamics?

Answer 6

-When energy is converted from one form to another, some of it becomes unavailable to do work

Question 7

What is a formula using enthalpy and entropy used to describe the second law of thermodynamics?

Answer 7

• Enthalpy (delta h) = Free Energy (delta G) + Entropy (Delta S) * Temp

Question 8

What is entropy?

Answer 8

The measure of unavailable energy in a system

Question 9

What is free energy?

Answer 9

the energy available to do work at a constant temperature

Question 10

What formula can be used to derive free energy?

Answer 10

• Delta G = Delta H - Delta S * T

Question 11

What must be true of delta G for reactions to occur spontaneously?

Answer 11

Delta G must be negative (releases free energy)

Question 12

What must be true of delta G if a reaction cannot occur spontaneously?

Answer 12

Delta G must be positive

Question 13

What is an Exergonic reaction?

Answer 13

One which releases energy/has a negative delta G

Question 14

Are catabolic reactions typicall exergonic or endergonic?

Answer 14

Exergonic

Question 15

What is an Endergonic reaction?

Answer 15

One which has a positive Delta G, i.e. the total free energy of the products is higher than that of the reactants, so external energy is required

Question 16

Delta G varies with conditions. Temperature and Pressure are relatively stable in biological systems. What other factor can influence it?

Answer 16

Concentration of the components of a reaction

Question 17

What is a general formula to describe how delta G varies with concentration of A and B?

Answer 17

Delta G = Delta G0 + RT ln ([C]c * [D]d)/[A]a * [B]b

Question 18

What are the two strategies to make a reaction proceed in the direction required by an organism?

Answer 18

• Make delta G negative by altering concentrations

- Couple a negative delta G reaction with a positive delta G reaction, so that the overall delta G is negative

Question 19

What are the functions of all the NTPS?

Answer 19

• CTP; lipid biosynthesis
• UTP; Carb biosyntheis
• ATP; energy carrier
• GTP; transmembrane signalling

Question 20

What is the free energy of hydrolysis of ATP?

Answer 20

Delta G Naught Prime = -30.5 kJ/mol

Question 21

What does delta G nought prime mean?

Answer 21

Components and products are 1M, but pH is 7.

Question 22

What makes ATP effective as a universal energy source for biological reactions?

Answer 22

• High enough delta G to drive many important metabolic processes, but small enough that it can be synthesised from available nutrients
• Has a negative delta G but does not spontaneously hydrolyse.
• Phosphorylation of ADP drives catabolism. Hydrolysis of ATP drives Anabolism, mechanical work, and active transport
• Adenine and Ribosyl make it able to bind to/regulate enzymes