Metabolism: Energy & Enzymes (Chapter 6)

Energy - the ability to do work

Kinetic Energy vs Potential Energy
Energy of Motion vs Stored Energy

First Law of Thermodynamics - the law of conservation of energy
Second Law of Thermodynamics - energy cannot be changed without a loss of useable energy (heat)

Metabolic Reactions
Reactants --> Products
Exergonic - releases energy | Endergonic = absorbs energy

ATP - the energy currency of cells (adenosine triphosphate)
Functions:
1. CHEMICAL WORK - Supplies energy needed to make macromolecules that make up the cell (and organism)
2. TRANSPORT WORK - Supplies energy needed to pump substances across the cell membrane
3. MECHANICAL WORK - supplies energy needed to make muscles contract and other cellular parts to move (flagella)

Metabolic Pathways & Enzymes (6-3)

Enzyme - protein molecule that functions as an organic catalyst to speed reactions
Substrate - reactants in the enzymatic reaction, this is what an enzyme attaches to
Energy of Activation - the energy required to cause the reaction

Properties of Enzymes:

Enzymes are made of proteins.
They speed up chemical reactions inside the cytoplasm.
They are needed only in small amounts
They remain unchanged after each reaction and can therefore be reused
Each enzyme is specific for a substrate

Induced Fit Model - substrates and enzymes fit together like a lock and key.
(Degradation vs Synthesis)

Factors Affecting Enzymatic Speed

1. Substrate concentration
2. Temperature & pH *
3. Enzyme concentration

Enzymes can be denatured - they change shape so much that they are no longer effective. High temp or pH can cause denaturation.

Siamese cats have an enzyme that works at lower temperatures only, causing the nose and ears to become a darker color than the rest of the body.

See animation of how an enzyme-substrate works.

Enzymatic Inhibition - when a substance binds to an enzyme and decreases its activity. (Usually reversible)

Competitive Inhibition
Noncompetitive Inhibition (allosteric site)

**Both are forms of feedback inhibition

Some inhibitors are NOT reversible - poisons like cyanide, lead poisoning all affect enzymes

QUESTION: What type of inhibition is pictured below?