Lec 22 COMBINED Thermodynamics/ Enzymes

Energy

The ability to do work

Metabolism

Catabolism + Anabolism

Catabolism

Breaking down of molecules to release energy

Anabolism

Building of molecules to store energy

First law of thermodynamics

The total amount of energy in the universe is constant. Energy is
neither created nor destroyed. It only changes form

Second law of thermodynamics

A system will tend towards an increase in entropy

Entropy

State of disorder/randomness

Gibbs free energy

The amount of energy in a system that can be useful work. DelatG represents the difference in the energies of reactants and products, and will describe the favorability of the reaction

Exergonic rection

Energy is released (DeltaG is negative)

Favorable reaction

Endergonic reaction

Energy is absorbed (DeltaG is positive)

Requires energy inpput

Reduction potential

The tendency of a chemical species to acquire electrons and become reduced. The more positive the potential, the greater the affinity for electrons

Enzyme

Biological catalyst. Lower the activation energy for a reaction. Usually proteins

Substrate

The reactants for a reaction that an enzyme acts upon

Active site

Part of the enzyme that acts upon a subtrate

induced fit model

Substrate binding the active site distorts the enzyme and the
substrate. Stabilizes the substrate molecules in their transition state

Enzyme kinetics

Quantitative analysis of enzyme catalysis and the rate of substrate
conversion to products. Dependent on substrate concentration

Allosteric inhibition

A type of non-competitive inhibition, stabilizes enzyme in inactive conformation.
Involved in feedback loops that regulate metabolic pathways.

Competitive inhibition

• inhibitor binds to the active site of an enzyme and compete directly with substrate
  molecules for the same site on the enzyme.

• Vmax is unchanged, Km increases

Non-competitive inhibition

• inhibitor binds outside the active site to lower enzyme activity.

• Vmax is lower, Km is unchanged.

What is energy? How do cells store energy for future use?

• Energy= The ability to do work or cause change

• Cells acquire energy through breakdown of molecules, which is then stored or used to fuel downstream processes

what are the first 2 law of thermodynamics?

• First law: The total amount of energy in the universe is constant. Energy is
  neither created nor destroyed. It only changes form

• Second law: A system will tend towards an increase in entropy
  

What is entropy?

a state of disorder/randomness

What is the relationship between the amount of energy in a molecule vs. its stability?

Inverse relationship (More energy →Less stable) Vice versa

What does it mean that a reaction is thermodynamically favorable? (Lecture 22, Slide 7)

Products have less energy than reactants (thermodynamically spontaneous) Does not necessarily mean the reaction will happen without some input

Why is the electronegativity of oxygen important for cellular respiration? (Lecture 22, Slide10,11)

Because it serves as the ultimate electron receiver, with movement of electrons it releases energy)

The oxidation of glucose is a highly thermodynamically favorable reaction. Why don’t marshmallows spontaneously combust? (And why is that a great thing in terms of being a cell that needs energy from glucose?) (Lecture 22, Slide 15)

Because the oxidation of glucose requires a catalyst

Why is stepwise energy release important for cells to obtain energy from glucose? (Lecture22, Slide 16)

Just incase it is needed throughout the steps which allows cells to store energy as ATP.

Why do enzymes function best at specific temperatures and pH? (Lecture 22, Slide 19)

Because specific temp. and pH gives the the best reaction rate for enzymes.

Why are enzyme kinetics important to consider? (Lecture 22, Slide 22)

Because it tells us how a reaction will progress within the cellular environment for a given enzyme.

What is the difference between a competitive and non-competitive inhibitor (Lecture 22, Slide 24)

Competitive- Inhibitor binds to the active site (compete with other substrate for same site) (Vmax is unchanged, Km increases)

Non-Competitive- Inhibitor binds outisde the active site to lower enzyme activity. (Vmax is lower, Km is unchanged)

Energy

Ability to do work or cuase a change

Cells store energy as?

• Electrochemical gradients (proton gradients)

• ATP

How do cells get energy?

Through breakdown of molecules, which is then stored or used to fuel downstream processes.

metabolism

Catabolism + Anabolism

Catbolism

Breaking down of molecules to release energy

Anabolism

Building of molecules to store energy

1st law of thermodynamics

Total amount of energy in the universe is constant. Energy is neither created nor destroyed. Only changes form.

Will energy transfer be 100% efficient?

It will never be 100% efficient, Some will be lost as heat, light, or noise

2nd law of thermodynamics?

System will tend towards an increase in entropy

Entropy

State of disorder/randomness

What makes a thermodynamically favorable reaction?

• Products have less energy than reactants (reactant have more energy than products)

• Moving from less stable to more stable releases energy

• Does not necessarily mean the reaction will happen without some input

Gibb’s Free Energy (G)

Amount of energy in a system that can do useful work. DELTAG represents the difference in the energies of reactants and products, and will describe the favorability of the reaction.

Exergonic reaction

• Energy released (DELTAG is negative)

• FAVORABLE reaction

Endergonic reaction

• Energy is absorbed (DELTAG is positive)

• REQUIRES energy input

A thermodynamically spontaneous reaction….

Has the capacity to happen but not might happen quickly

Reduction potential

• The tendency of a chemical species to acquire electron and become reduced.

• The more positive the potential, the greater the affinity

Electronegativity

Related to the reduction potential

What element is the one of the most electronegative?

Oxygen

Why does glucose have a lot of potential energy?

Because it has many C-H bonds, which makes it as the main source of energy for cells.

Respiration

• Oxidation of glucose into carbon dioxide and water to produce ATP

• EXERGONIC, highly favorable reaction

Respiration Equation

C6H12O6 + 6O2 → 6CO2 + 6H2O + ATP (-686 kcal/mol)

Enzyme

Biological catalysts. LOWER the activation energy for a reaction (Usually proteins)

Substrate

Reactants for a reaction that an enzyme acts upon

What conditions effect most biological enzymes?

• Temperature dependence

• pH dependence

Active site

• Part of the enzyme that acts upon a substrate

• Confers specificity between enzyme and substrate

Induced fit model

Substrate binding the active site distorts the enzyme and the substrate. Stabilizes the substrates molecules in their transition.

Enzyme kinetics

Quantitative analysis of enzyme catalysis and the rate of the substrate conversion to products. Dependent on the substrate concentration

Why is enzyme kinetics important

Because it tells us how a reaction will progress within the cellular environment for a given enzyme

What are the 2 types of inhibition?

• Competitive inhibition

• Non-competitive inhibition

Competitive inhibition

• Inhibitors binds to the active site of an enzyme and compete directly with substrate molecules for the same site on the enzyme.

• Vmax is UNCHANGED

• Km INCREASES

Non-competitive inhibition

• Inhibitor binds OUTSIDE the active site to lower enzyme activity.

• Vmax is LOWER

• Km is UNCHANGED

Allosteric inhibition

A type of non-competitive inhibition, stabilizes enzyme in inactive conformation. Involved in feedback loops that regulate metabolic pathways