4 and 5 - Bioenergetics and ATP

Question 1

Enthalpy, entropy and free energy are state functions, meaning?

Answer 1

That they depend only on the beginning and final states, and not on the trajectory between those states

Question 2

First Law of Thermodynamics

Answer 2

Total energy is constant. Energy can be converted from one form to another, but it cannot be created or destroyed.

Question 3

Second Law of Thermodynamics

Answer 3

There is a tendency towards increasing disorder. The disorder is referred to as entropy

Question 4

If enthalpy (ΔH) is negative

Answer 4

The reaction gives off heat and is exothermic

Question 5

If enthalpy (ΔH) is positive

Answer 5

The reaction takes in heat from its surroundings and is endothermic

Question 6

If ΔH = 0

Answer 6

No heat is exchanged, Isothermic

Question 7

If ΔG is negative the reaction is ___ and ____

Answer 7

Reaction is exergonic and is spontaneous

Question 8

If ΔG is positive the reaction is ____ and ___

Answer 8

Reaction is endergonic and is not spontaneous (energy is required)

Question 9

If ΔG = 0 the reaction is?

Answer 9

Reaction is in equilibrium

Question 10

What is ΔG*?

Answer 10

Definable standard free energy, all reactions have this. Under standard conditions.

Question 11

What is ΔG’?

Answer 11

ΔG* but also where the pH is close to 7 and where the concentration is ~ 1 x 10^-7 M. If it is a biolical reaction, the ΔG* will often be positive and coupled with a negative ΔG’

Question 12

What does catalysis do?

Answer 12

Reduces the activation energy needed for a reaction

Question 13

What does anhydride mean?

Answer 13

Without water

Question 14

What are the 2 main structural components of ATP (not including adenosine)

Answer 14

Two phosphoanhydride bonds formed between two phosphoryl groups

Question 15

What are three main reasons for ATP storing energy?

Answer 15

Charge repulsion between negative phosphates

Hydration, ATP hydrolysis products are more easily solvated than ATP as a whole (to get greater entropy).

Resonance, competition between phosphoanhydride bonds and neighbouring phosphoryl groups for the O electrons.

Question 16

Creatine Kinase does what?

Answer 16

catalyzes the conversion of ADP to ATP while simultaneously converting phosphocreatine to creatine (phosphate group transfered from phosphocreatine to ATP). ATP + creatine = ADP + phosphocreatine

Question 17

What is substrate-level phosphorylation?

Answer 17

Where a high energy compound donates a phosphate group to ADP forming ATP (eg phosphocreatine giving phosphate group to ADP to form ATP and creatine)

Question 18

What is enthalpy?

Answer 18

Total heat content of a system

Question 19

What is entropy?

Answer 19

State of disorder of a system

Question 20

What is free energy?

Answer 20

Energy available to do chemical work

Question 21

What is a state function? List three that are important to thermodynamics

Answer 21

Functions that depend only on the beginning and final states, and not on the trajectory between those states, we are only interested in change.

Enthalpy, entropy and free energy are all state functions.

Question 22

How is the hydrophobic effect supported by thermodynamic principles?

Answer 22

The aggregation of hydrophobic particles decreases the surface area of their contact with water, increasing its entropy. The free energy then is negative (ΔG = ΔH - TΔS) because ΔS is positive, meaning the reaction is spontaneous.

This spontaneous exclusion of water is important in membrane formation and protein folding

Question 23

How is ΔG’ correlated with phosphoryl transfer potential?

Answer 23

A very negative ΔG is correlated with a high phosphoryl transfer potential. That is, that when a phosphate group is transferred to something to release energy (eg. hydrolysis of ATP), this reaction is highly exergonic and also spontaneous.

Question 24

Why type of energy does the hydrolysis of ATP to ADP + Pi provide?

Answer 24

It provides free energy that can drive coupled reactions

Question 25

What types of bonds exists between ATP’s phosphate groups?

Answer 25

Phosphoanhydride bonds

Question 26

Whay types of bonds exists between the 5’ carbon of adenosine and the phosphate group, in ATP?

Answer 26

phosphoester bonds

Question 27

How can phosphocreatine replenish ATP? (answer: because…)

Answer 27

Because phosphocreatine hydrolysis is more exergonic under standard conditions than is ATP hydrolysis.

Question 28

Where is phosphocreatine most commonly found in the body?

Answer 28

Where ATP is most rapidly turned over

Muscles and the nervous system