Honors Biology - Unit 5

Activation energy

The minimum amount of energy required to start a chemical reaction.

Active site

The specific region on an enzyme where the substrate binds.

Aerobic respiration

Respiration that requires oxygen and produces large amounts of ATP.

Anabolism

Metabolic pathways that build larger molecules from smaller ones (requires energy).

Anaerobic respiration

Energy production without oxygen; produces much less ATP.

ATP

the cell’s main energy molecule.

ADP

lower-energy form that becomes ATP when a phosphate is added.

ATP synthase

An enzyme in mitochondria that makes ATP using energy from a proton gradient.

Calorie

A unit of energy; the amount of energy needed to raise 1 g of water by 1°C.

Catabolism

Metabolic pathways that break down molecules into smaller pieces (releases energy).

Catalyst

A substance that speeds up a reaction without being used up.

Catalytic cycle

The sequence of steps an enzyme follows: bind substrate → transform → release product → enzyme reused.

Cellular respiration

Process that converts glucose and oxygen into ATP, CO₂, and water.

Chemical energy

Energy stored in chemical bonds of molecules.

Concentration

The amount of a substance in a specific volume of solution.

Denature

When a protein (like an enzyme) loses its shape due to heat, pH, or other factors—making it unable to function.

Electron transport chain (ETC)

A series of proteins in mitochondria that transfer electrons to produce ATP.

Endergonic reaction

A reaction that requires energy input; products have more energy than reactants.

Energy coupling

Using energy released by exergonic reactions to power endergonic reactions.

Exergonic reaction

A reaction that releases energy.

Enzyme

A biological catalyst that speeds up chemical reactions in cells.

Enzyme-substrate complex

Temporary structure formed when an enzyme binds its substrate.

Ethanol

A 2-carbon alcohol produced during alcoholic fermentation.

FAD

Electron carriers in respiration.

FADH2

the high-energy, reduced form of FAD.

Fermentation

Anaerobic process that regenerates NAD⁺ and produces small amounts of ATP.

Glycolysis

First step of cellular respiration; splits glucose into pyruvate and makes 2 ATP.

Induced fit model

Theory that the enzyme changes shape slightly to fit the substrate perfectly.

Kinetic energy

Energy of motion.

Krebs cycle (citric acid cycle)

Second stage of aerobic respiration; produces electron carriers (NADH, FADH₂), CO₂, and a little ATP.

Lactic acid

Produced in muscle cells during anaerobic respiration (lactic acid fermentation).

Law of conservation of energy

Energy cannot be created or destroyed—only transformed.

Lock and key model

Theory that the enzyme’s shape exactly matches the substrate (older model).

Mechanical energy

Energy associated with movement or position of objects.

Metabolism

All chemical reactions that occur in an organism (anabolism + catabolism).

Mitochondria

Organelles where most ATP is produced; “powerhouse of the cell.”

Mitochondrial cristae

Folded inner membranes of mitochondria where the ETC occurs.

Mitochondrial matrix

The innermost space in mitochondria where the Krebs cycle happens.

NAD+

Electron carrier in respiration.

NADH

the high-energy, reduced form of NAD+.

pH

A scale measuring how acidic or basic a solution is.

Potential energy

Stored energy based on position or structure.

Product

The molecule(s) produced by a chemical reaction.

Radiant energy

Energy carried by light.

Respiration

Process of breaking down food molecules to release energy.

Substrate

The molecule on which an enzyme acts.

Temperature

A measure of the average kinetic energy of particles; affects enzyme activity.

Thermal energy

Heat energy resulting from particle movement.

Anaerobic

Which respiration pathway extracts energy without the use of oxygen?

Glucose

What molecule is energy extracted from in cellular respiration?

Glycolysis

Aerobic and anaerobic respiration both begin with what first step?

The cytoplasm

Where does glycolysis happen?

2 ATP

How many ATP are needed to split a sugar molecule in two?

Krebs cycle

Carbon dioxide is produced as a waste product at what stage of respiration?

34-36 ATP

How much ATP is aerobic respiration capable of making for every glucose molecule?

2 ATP

How much ATP is anaerobic respiration capable of making for every glucose molecule?

The muscles

Lactic acid fermentation happens where?

c. Water

Which of the following is not a reactant of cellular respiration?

a. Oxygen

b. Glucose

c. Water

d. All of these are reactants

d. Oxygen

Which of the following is not a product of cellular respiration?

a. Carbon dioxide

b. ATP

c. Water

d. Oxygen

Mitochondria

In which cell organelle does aerobic cellular respiration take place?

Carry electrons

What role do NADH & FADH2 play in cellular respiration?

c. break glucose into 2 pyruvate molecules

What is the purpose of glycolysis?

a. Break down pyruvate to generate NADH

b. Use electrons from NADH and FADH2 to generate ATP

c. Break glucose into 2 pyruvate molecules

d. Produce CO2 from the break down of pyruvate in anaerobic conditions

b. Use electrons from NADH and FADH2 to generate ATP

What is the purpose of the ETC?

a. Break down pyruvate to generate NADH

b. Use electrons from NADH and FADH2 to generate ATP

c. Break glucose into 2 pyruvate molecules

d. Produce CO2 from the break down of pyruvate in anaerobic conditions

a. Break down pyruvate to generate NADH and release CO2 as waste

What is the purpose of the Krebs cycle?

a. Break down pyruvate to generate NADH

b. Use electrons from NADH and FADH2 to generate ATP

c. Break glucose into 2 pyruvate molecules

d. Produce CO2 from the break down of pyruvate in anaerobic conditions

d. Produce some ATP from the break down of pyruvate in anaerobic conditions

What is the purpose of fermentation?

a. Break down pyruvate to generate NADH

b. Use electrons from NADH and FADH2 to generate ATP

c. Break glucose into 2 pyruvate molecules

d. Produce CO2 from the break down of pyruvate in anaerobic conditions

Alcoholic fermentation

Which process makes the CO2 bubbles that make bread rise?

Matrix

The Krebs Cycle happens in which part of the mitochondria?

Oxygen

What is the last molecule the electrons are accepted by in the ETC?

Aerobic respiration

Which process is most efficient at generating ATP? Aerobic or anaerobic respiration?

a. 1st Law of Thermodynamics

Which of the following is demonstrated when plants convert light energy into chemical potential energy?

a. 1st law of thermodynamics

b. 2nd law of thermodynamics

c. Entropy

d. Exergonic reaction

Exergonic reaction

In what reaction is energy being released? Endergonic or Exergonic?

Endergonic reaction

In what reaction is energy required (absorbed)? Endergonic or Exergonic?

Exergonic

Exergonic, Endergonic or Both? ATP dropping a P and becoming ADP

Endergonic

Exergonic, Endergonic or Both? Phosphorylating ADP to form ATP

Both

Exergonic, Endergonic or Both? Energy coupling

Exergonic

Exergonic, Endergonic or Both? Cellular Respiration

False

True or false? Cellular respiration only happens in animals.

False

True or false? Cellular respiration only happens in plants and animals.

False

True or false? Cellular respiration only happens in bacteria.

d. Amount of water present

Which of the following would NOT influence the rate of cellular respiration?

a. Temperature

b. Activity level

c. Amount of glucose present

d. Amount of water present

False

T or F: Once NADH and FADH2 drop off their electrons at the ETC, the NAD+ and FAD are released by the cell as waste.

glucose + oxygen --> carbon dioxide + water + ATP

What is the correct equation for cellular respiration?

glycolysis --> Krebs cycle --> ETC

What is the correct sequence of aerobic respiration?