Lecture 5 (Chris Allen)

Question 1

Wha is thermodynamics

Answer 1

The study of the energy transformations that occur in a system (a collection of matter).

Question 2

What is the first law of thermodynamics (The Conservation of Energy)

Answer 2

Energy is neither created or destroyed. It is just transformed from one form to another.

Question 3

What is the second law of thermodynamics

Answer 3

When energy changes from one form to another, or matter moves freely, entropy increases.

Question 4

How do enzymes increase the rate of a chemical reaction

Answer 4

• An enzyme catalysed a reaction by lowering the activation energy barrier.
• This enables the reactant molecules to absorb enough energy to reach the transition state.
• This enables a cell to have a dynamic metabolism, routing chemicals smoothly through metabolic pathways.

Question 5

How do enzymes specify the type of chemical reactions that take place

Answer 5

The reaction catalysed by each enzyme is very specific as only one specific substrate molecule is complementary in shape to an enzyme’s active site.

Question 6

How enzymes allow chemical reactions to be coupled together

Answer 6

• Energy coupling is the use of an exergonic process to drive an endergonic process.
• The overall free-energy change for a chemically coupled series of reactions is equal to the sum of the free-energy changes of the individual steps.
• Under standard reaction conditions the endergonic process would not proceed alone at equimolar concentrations.
• Enzymes facilitate this coupling process which allows energy conservation in biochemical processes.

Question 7

How do enzymes facilitate energy transduction

Answer 7

• Energy transduction is the conversion of energy from one form to another.
• Due to thermodynamics, most energy is dissipated as heat during a chemical reaction which increases the entropy of the surroundings.
• For example, very little of the energy supplied by glucose is transformed into kinetic energy, the majority of the energy is lost as heat.
• Enzymes conserve energy and facilitate transduction into other forms.

Question 8

When may a reaction occur spontaneously

Answer 8

When delta G is less than 0.

Question 9

What does the standard free energy change (🔼G0’) depend upon

Answer 9

• Depends on the nature of the reactants.
• Depends on the environment of the reaction e.g. pH: assumes a pH of 7.
• Is based on reactant and product concentrations of 1M.

Question 10

What do enzymes not affect

Answer 10

The free energy change for a reaction (🔼G).