Enzymes and Ribozymes

What do reactants yeild?

Products

Spontaneous chemical reactions

chemical reactions that will occur under current circumstances

Nonspontaneous chemical reactions

chemical reactions that will not occur under current circumstances, but will occur with assistance

-Most reactions in the cell are nonspontaneous

What happens to energy when a chemical raction occurs?

It is lost (expelled) through heat, light, etc.

Activation Energy (E_a)

The energy required for a chemical reaction to occur

How do you “speed up” (Make spontaneous) chemical reactions?

-Increase temperature

-Increase pressure

-Increase the amount of reactants

-Increase surface area

-Add a catalyst (best option for cells)

Catalysts

chemicals that lower the energy needed to activate a reaction (the “hump”)

-Speeds up a chemical reaction without being used up in the reaction

Enzyme

Catalyst made of protein

-Often ends in -ase

Ribozyme

Catalyst made of RNA

Are Enzymes and ribozymes specific?

yes, most only interact with and affect a single substrate

Substrate

-The target molecule of a catalyst

-Bonds to the active site, where the catalysis occurs

How are enzymes and ribozymes be so specific?

A substrate fits perfectly into the active site of the enzyme

Induced fit theory

The enzymes’ active site folds around the substrate, causing the reaction to occur

The Reaction Cycle

1. The substrate binds to the enzyme in the active site

2. The enzyme-substrate complex (E-S complex) preforms the chemical reaction

3. The new product is released, and the enzyme searches for a new substrate

Are enzymes sensitive to external factors?

yes- even slight changes in pH and temperature can have big effects

-Changes affect tertiary and quaternary structures (Changes the shape of the enzyme)

Coenzymes

Chemicals required for enzymes to carry out their reactions

-Binds to the active site along with a substrate

Competitive inhibition

a regulator physically blocks the active site

-Must compete for the active site with the normal substrate

Noncompetitive inhibition

a regulator has its own binding site

-changes the shape of the active site

Catalysis

the acceleration of a chemical reaction by a catalyst