WK 7: Bioenergetics and Thermal Dynamics

Question 1

1. Describe how energy is stored and utilised in living organisms.

Answer 1

energy is stored chemically in biomolecules –> converted into ATP–> and utilised by the cell to maintain life and order through mechanical, gradient and synthetic work.

Biomolecules (e.g. lipids, carbohydrates and proteins) store energy in their chemical bonds.

When energy is needed: these molecules are broken down in a series of biochemical reactions releasing energy, which is used to make ATP, the cell’s main energy carrier.

ATP role is to perform biological work:
1. Mechanical work: movement and contraction

2.Gradient work: pumping ions across membranes

3. Synthetic work: building molecules like proteins and DNA

what its used for:
1- returned to surroundings as heat
2- some molecules are end-products which are simpler and LESS ORGANISED than original source of energy (increasing randomness of universe)
3-used to produce complex macromolecules (decrease randomness)

Question 2

2. Explain the processes of energy transformation in biological systems.

Answer 2

1. living organisms use an external source of energy like food and light
2. ENERGY IS TRANSFORMED USING BIOCHEMICAL REACTIONS (chemical transformation)
3. to obtain energy from biomolecules they are converted into other molecules like ATP after several biochemical reactions
4. ATP is the product of transformation known as energy currency, and is principle molecule for storing and transferring energy in cells.

Question 3

R3. What is thermodynamics and the laws of thermodynamics

Answer 3

Thermodynamics is the study of the relationship between heat, work, temperature and energy.

Biochemical reactions, follow the laws of thermodynamics:

First law of thermodynamics: the total amount of energy in the universe remains constant, although the form of energy may change

Second law of thermodynamics: the universe always tends towards increasing disorder (entropy), in all natural processes the entropy of the universe increases

Question 4

3. Analyze how the flow of energy and matter in a cell adheres to the laws of thermodynamics.

Answer 4

Transform energy from external source: 1st law : Conservation of energy

Create randomness: 2nd law: The universe favours disorder

First law of thermodynamics:
Living organisms are open systems constantly exchanging material and energy:

EXAMPLES: Energy is converted from one type to another, but it cannot be destroyed

Potential energy from chemical bonds is converted into kinetic energy (heat and mobility)

SECOND LAW: living cells use energy to do work, to create and maintain the order:

Transform energy from external source (following the first law of thermodynamics)

Create randomness in the universe (following the second law of thermodynamics)

Question 5

4. Discuss the roles of heat and entropy in determining variations in free energy.

Answer 5

1. Variations in Gibbs free energy (ΔG) are determined by the balance between “the tendency to achieve the most stable bonding state (enthalpy, ΔH)” and “the tendency to achieve the highest degree of randomness (entropy, ΔS) in the universe.”
2. Reactions are thermodynamically favourable (ΔG < 0) when they “release energy in the form of heat (ΔH < 0)” and/or “increase the disorder of the system (ΔS > 0).”
3. The direction of a chemical reaction depends on ΔG, which is influenced by “experimental conditions, concentration of molecules, and the standard free energy change (ΔG°’).”
4. At equilibrium, “ΔG = 0” and the rates of the forward and reverse reactions are equal.
5. This flow of energy in cells aligns with the first law of thermodynamics (energy is transformed, not created or destroyed) and supports the second law, as cells produce internal order while increasing “the overall entropy of the universe.”

The flow of energy in biochemical reactions is influenced by two forces:

1. The tendency to achieve the most stable bonding state (enthalpy, H)
2. The tendency to achieve the highest degree of randomness (entropy, S) in the universe

Cells require sources of Gibbs free energy

Question 6

R4. What is Gibbs free energy and its function

Answer 6

The energy required to generate work in a biological system when temperature is constant (isothermal system)

function: predict the direction of chemical reactions and the amt. of work performed at constant temp. (whether thermodynamically favourable)

Change in Gibbs free energy= (enthalpy change)- temperature *(entropy change)

Question 7

6. Differentiate between thermodynamics and kinetics in biochemical reactions.

Question 8

8. Describe how the flow of electrons in redox reactions generates energy in cells.

Answer 8

The flow of electrons in oxidation-reduction reactions is responsible, directly or indirectly, for all work done by living organisms
In cells, energy is generated through redox (oxidation-reduction) reactions, where electrons are transferred from one molecule (the electron donor) to another (the electron acceptor). This flow of electrons releases free energy, which can be captured and used to do biological work.