Bioenergetics: The role of ATP (Chapter 11)

Question 1

What is Bioenergetics?

Answer 1

Study of Energy Change in Biochemical Processes

Question 2

Define: Starvation

Answer 2

Depletion of energy resources

Question 3

Define: Marasmus

Answer 3

Malnutrition due to energy deficiency

Question 4

Define: Metabolic Rate

And what controls the Metabolic rate?

Answer 4

Rate of energy release.

Controlled by Thyroid Hormones

Question 5

Define: Gibbs free energy(chemical potential)

Answer 5

The portion of energy which is available to do work. In other words:
- Useful energy.

Question 6

What is the First Law of Thermodynamics?

Answer 6

The total energy of a system and it’s surroundings remains constant.

Question 7

What is the Second Law of Thermodynamics?

Answer 7

With EVERY spontaneous reaction, there must be an INCREASE in Entropy.

Question 8

What is an Exogonic Reaction?

Answer 8

Reaction which:

• has a negative Gibbs free energy change
• irreversible
• spontaneous

Question 9

What is an Endogonic Reaction?

Answer 9

Reaction which:

- has a positive Gibbs free energy

Question 10

What happens when the change in Gibbs Free Energy = 0

Answer 10

The reaction is at equilibrium

Question 11

What is the conditions for “Standard Free Energy” in Biological Systems?

Answer 11

ph=7

Question 12

What reaction is Anabolism, Catabolism?

Answer 12

Catabolism = Exogonic Rxns
Anabolism = Endogonic Rxns

Catabolism + Anabolism = Metabolism

Question 13

What is coupling?
What two types are there?
Advantage of one method over the other?

Answer 13

A endogonic reaction can be coupled to a exogonic reaction so that it is made possible.

Either can be done by:

1) Making a common obligatory Intermediate
- A+B = I = C + D
- Useful because it has an “inbuilt mechanism for control of oxidation”
- Useful in respiratory control as rate of utilisation of D controls rate of oxidation of B.

2) Synthesising a high energy potential compound
- this can then be incorporated into the endogonic reaction

Advantage:
-Compound of high energy potential does not need to be structurally related to reactant/produce.

Question 14

Autotrophic vs Heterotrophic Organisms

Answer 14

Autotrophic:

• Obtain free energy from “simple exogonic processes”
• like sunlight

Heterotrophic:
- These couple their metabolism to breakdown of complex organic molecules in the environment.

Question 15

Role of ATP in coupling?

How does ATP function as?

Answer 15

Transfers free energy from exogonic to endogonic reaction.

It functions as a Mg2+ complex.

Question 16

Compare ATP, ADP and AMP in terms of energy

Answer 16

• ATP has two high energy anhydride bonds.
• ADP has one high energy anhydride bond
• AMP has one LOW energy ester bond.

Question 17

What are:

• High Energy Phosphates?
• Low Energy Phosphates?

Answer 17

High Energy Phosphates:

-free energy change > ATP’s
-Usually:
- Anhydrides/ Endophosphates/ phosphoguanidines
Eg/
1,3 Bisphosphoglucerate, Creatine Phosphate, Arginine Phosphate, Phospoenolpyruvate

Low Energy Phosphates:

-Free energy change

Question 18

Reason for High Free Energy change of ATP?

Answer 18

Due to :

• relief of charge of repulsion between adjacent negatively charged oxygen atoms
• stabilisation of reaction products (especially phosphate as a resonance hybrid…)

Question 19

Uses of ATP?

Answer 19

1) Energy Currency
2) Donates phosphates for phosphorylation reactions
3) Precursor of cAMP
4) acts as a co-transmitter which acts on PURIGENIC Receptors

(something to do with gut relaxation, if we get asked this I’m going back to England and will live on welfare… without a degree, or any form of education. Fucking purigenic receptors, do they think this is physiology?)

Question 20

Major Sources of High Energy Phosphates (source of ATP)

Answer 20

1) oxidative phosphorylation

2) Glycolysis - net formation of 2P
- catalysed by pyruvate kinase

3) Substrate level phosphorylation in Citric Cycle
- one P generated
4) Phosphagens

Question 21

What does Adenylate Kinase (Myokinase) do?

- write the reaction and state what it is useful for?

Answer 21

-Interconverts Adenine Nucleotides.

AMP + ATP = 2ADP

It allows:

1) ADP to be used to synthesise ATP
2) AMP to be rephosphorylated to form ADP
3) When ATP concentration is down, AMP concentration increases, acting like a signal for more generation of ATP.

Question 22

Role of ACYL-CoA Synthease

How is the reaction ensured to be irreversible? (write the equation).

Answer 22

Converts ATP directly to AMP when activating long chain fatty acids.
Reaction has loss of free energy.

Ensures irreversibility by:
- hydrolytic splitting of PPi
PPi + H20 -> 2Pi
Done by Inorganic Pyrophosphatase.

Question 23

What does:
Nucleotide Diphosphate Kinase (NDP) do?

Write the equation.

Answer 23

NDP makes Nucleoside triphophates from their diphosphates.

ATP + NDP NTP + ADP

Question 24

What does:

Nucleotide Monophosphate Kinase (NMP) do?

Answer 24

Nucleoside Monophophate makes Diphosphates from their monophosphates.

Question 25

What are Phosphogens?
Name the ones found in vertebrates/Invertebrates?
How do they help in Muscle contraction?

Answer 25

They are:
- storage forms of high energy phopshates.

Vertebrates: Creatine Phosphate
Invertebrates: Arginine Phosphate

Allows maintenance of ATP during muscle contract because when ATP:ADP ratio increases, the concentration of phosphogens always increases.