energy and metabolism exam 2

How do enzymes increase the speed of a chemical reaction?

• Lowers the activation energy*

• Each enzyme is specific to one or more reactions

• Shaped to stabilize the transition state

How does an enzyme’s environment dictate its evolution and activity?

• Enzymes evolve for different optimal conditions

• Enzymes function best at a specific pH

• pH alters acidic/basic amino acids and prevents ionic bonds

What is negative feedback?

Products of a reaction or pathway inhibit an enzyme in the pathway, reading the production of the product

Endergonic (non-spontaneous)

• Absorbs energy

• Energy in reactants < energy in products

• Anabolic (smaller to bigger)

Exergonic (spontaneous)

• Releases energy

• Energy in products < energy in reactants

• Catabolic (bigger to smaller)

Biosynthetic

• Anabolic

• simpler → complex molecules

Anabolic

• Biosynthetic

• simpler → complex molecules

• Consume energy

Catabolic

• degradative

• Larger → smaller molecules

• Releases energy

△G

• Change in Gibbs free energy

• △G = G(products) - G(reactants)

What are two categories and three ways we discussed in class for stimulating chemical reactions to move in the non-spontaneous direction? Explain in detail how each works.

Categories:

1. Manipulating reactant and product concentrations to favor the reaction

2. Energy coupling: coupling an exergonic reaction to an endergonic reaction

Ways to stimulate:

1. Temperature

2. pH 

3. Increasing substrate concentration

What is the role of ATP in the cell?

ATP powers most cellular work and creates the cell’s usable energy

How does phosphorylation lend energy to cellular processes? Give two different types of examples and be as specific as you can.

Phosphorylation: the process of adding a phosphate group to another molecule

• Creates an unstable intermediate that favors the production of the final product

• Involving phosphate group ties phosphorylation to another process

1. Active transport

2. Motor proteins