NAS 2 - Reactions/Energy

What is a chemical reaction?

A process that breaks and forms chemical bonds, converting reactants into products.

What is a reactant?

A starting substance in a chemical reaction.

What is a product?

A substance formed by a chemical reaction.

What is a chemical equation?

A symbolic representation of a chemical reaction.

What is the law of conservation of matter?

Matter is neither created nor destroyed during a chemical reaction.

What happens to atoms during a chemical reaction?

They are rearranged into new combinations.

What is a catalyst?

A substance that speeds up a reaction without being consumed.

What is an enzyme?

A biological catalyst, usually a protein.

How are catalysts and enzymes related?

Enzymes are catalysts used by living organisms.

What is activation energy?

The minimum energy needed to start a reaction.

Why is activation energy needed?

To begin breaking existing chemical bonds.

Do catalysts change the energy released?

No. They only lower activation energy.

Are enzymes used up?

No. They can be reused.

Breaking bonds requires what?

Energy input.

Forming bonds does what?

Releases energy.

What is an exergonic reaction?

A reaction that releases energy.

What is an endergonic reaction?

A reaction that requires energy input.

Reactants vs. products?

Reactants start the reaction; products are formed.

Catalyst vs. enzyme?

All enzymes are catalysts, but not all catalysts are enzymes.

Why are enzymes essential?

They speed reactions enough to support life.

Why is digestion slow without enzymes?

Digestive reactions occur too slowly.

Exam Trap: Does a catalyst become part of the product?

No.

Exam Trap: Can catalysts make impossible reactions possible?

No. They only speed possible reactions.

Rapid Recall: Starting substances?

Reactants.

Rapid Recall: Biological catalyst?

Enzyme.

What is a synthesis reaction?

A reaction that combines smaller substances into a larger, more complex substance.

What is another name for a synthesis reaction?

An anabolic reaction.

Why are synthesis reactions called anabolic?

They build larger molecules from smaller ones.

Do synthesis reactions require or release energy?

They require energy (endergonic).

Example of a synthesis reaction?

Amino acids joining to form a protein.

What is dehydration synthesis?

A synthesis reaction that removes water as a bond forms.

What is a decomposition reaction?

A reaction that breaks a large molecule into smaller molecules.

Another name for a decomposition reaction?

A catabolic reaction.

Why are decomposition reactions called catabolic?

They break down larger molecules.

Do decomposition reactions usually release energy?

Yes, they are usually exergonic.

Example of decomposition in the body?

Digestion of carbohydrates into glucose.

What is hydrolysis?

A decomposition reaction that uses water to break bonds.

Dehydration synthesis vs. hydrolysis?

Dehydration removes water to build; hydrolysis adds water to break apart.

What is an exchange reaction?

A reaction where atoms or groups of atoms are exchanged.

Why are exchange reactions important?

They rearrange molecules during metabolism.

What is a reversible reaction?

A reaction that can proceed in both directions.

What is chemical equilibrium?

Forward and reverse reactions occur at equal rates.

Does equilibrium mean reactions stop?

No. They continue equally in both directions.

Why is protein synthesis anabolic?

It builds proteins from amino acids.

Why is digestion catabolic?

It breaks large food molecules into smaller ones.

Exam Trap: Are anabolic reactions energy releasing?

No. They require energy.

Exam Trap: Does hydrolysis build larger molecules?

No. It breaks them apart.

Rapid Recall: Which reaction builds molecules?

Synthesis (anabolic).

Rapid Recall: Which reaction breaks molecules?

Decomposition (catabolic).

Rapid Recall: Which reaction uses water to split molecules?

Hydrolysis.