Bioenergetics

Question 1

Define Bioenergetics

Answer 1

Quantitative study of energy transformations and exchanges upon which all life depends

Study of the nature and function of the chemical processes underlying energy transformation and exchange

Question 2

What does it mean by Biological systems being open?

Answer 2

They can absorb energy from, and give energy back to their surroundings

Question 3

What is the use of the ATP cycle?

Answer 3

Linking energy release and utilisation within cells

Question 4

What is the first step in the ATP cycle?

Answer 4

Energy sources enter such as stored nutrients, ingested foods and solar photons

ADP converted to ATP

Question 5

What is the second step of ATP cycle

Answer 5

Catabolic reactions

Exergonic: free energy released from stores converted to ATP

Question 6

What is the third step of ATP cycle

Answer 6

Heat energy dissipated to surroundings

Question 7

What is the forth step of ATP cycle?

Answer 7

Anabolic reactions: Endergonic: Free energy stored in ATP released to maintain biological systems

ATP converted to ADP

Question 8

What is the final step of ATP cycle

Answer 8

Complex biomolecules cellular work (such as mechanicla osmotic) released

Question 9

Define free energy

Answer 9

The portion of the energy of a system capable of doing work

Results from the difference in atoms and bonds present in reactants and products

Question 10

Define enthalpy

Answer 10

Living animals can’t use heat energy to do work

Essentially Isothermal
Temperature throughout the system is uniform

Enthalpy change also has a disorder component (entropy)

Unavailable for work in biological systems

Question 11

What does biological systems use to drive living processes?

Answer 11

Chemical energy

Question 12

Define Gibbs free energy (G)

Answer 12

Chemical energy avaible for work

G is related to enthalpy change and entropy

Question 13

Define Exergonic reactions

Answer 13

Have Negative Delta G

Products have less free energy than reactants

Free energy released is available for work

Reactions will be spontaneous

Question 14

Define Endergonic reactions

Answer 14

Energy is absorbed or entropy decreases

Has positive Delta G

Products have more free energy than reactants

Input of free energy is required

Reactions will not process spontaneously

Question 15

Define spontaneous in relation to Endergonic and exergonic

Answer 15

Doesn’t mean instantaneous

Delta G is a measure of whether a reaction is spontaneous

Does not predict rate of reaction or stability of reactants

Question 16

When is a reaction spontaneous?

Answer 16

Large, negative free energy change occurs

ATP is very stable

Only breaks down when catalysis is present to reach activation energy

Question 17

Explain large negative free energy change on a molecular level

Answer 17

ATP as an example

Products are more stable than reactants

Electrostatic repulsion requires energy to be removed

Phosphate and ADP seperate nicely through hydrolysis

Energy released with addition release of free energy because product is rearranged

Ionisation used to get product into more stable form

Question 18

Define Resonance stabilisation

Answer 18

Pascal negative charge on all the oxygens

Question 19

Free energy change is due to?

Answer 19

The sum of all atoms and bonds present in reactants and products

Question 20

Free energy of high energy phosphates not due to hydrolysis alone, what else?

Answer 20

Type of bonding reactants and products is also important

Free energy of hydrolysis is large because keto form of pyruvate is more stable

Free energy of hydrolysis is large because of resonance stabilisation

Question 21

What is ATP hydrolysis like in free solution?

Answer 21

Loss of free energy of hydrolysis as heat

ATP is only a useful transducer of free energy because free energy of hydrolysis is coupled via group transfer

Question 22

Explain coupled reactions

Answer 22

Share a common intermediate therefore can link

The reactions can be coupled because they have phosphate as a common intermediate

Often involved activated enzyme intermediates

Phosphorylation of the enzyme provides sufficient energy for group transfer

Question 23

Why is ATP hydrolysis used in coupled reactions?

Answer 23

Couples to another reaction makes the overall reaction energetically favorable

Question 24

What can we predict from Delta G

Answer 24

The direction in which a reaction will proceed

The equilibrium position

The amount of work a chemical reaction can theoretically perform

Question 25

How are Delta G and Equilibrium constant of a reaction related?

Answer 25

For reactions of this type: A + B C + D

Composition of reactants and products in a system will change constantly until equilibrium is reached

Rates of the forward and reverse reactions are the same as equilibrium

No net change in [reactant] and [product] at equilibrium

Ratio of [product] and [reactant] at equilibrium determine equilibrium constant

Question 26

What is the 1st law of thermodynamics?

Answer 26

The energy of the universe is constant: Energy may change form or be transported from one region to another but it cannot be created or destroyed

Question 27

What is the 2nd law of thermodynamics?

Answer 27

In all natural processes, the entropy of the universe increases:

Every energy transfer or transduction increases the entropy of the universe

Increase in entropy need not be within the observed system