OPENSTAX Bio Carbs Thermodynamics enzymes and respiration

What elements make up carbohydrates?

Carbon (C), Hydrogen (H), and Oxygen (O).

What is the monomer of carbohydrates?

Monosaccharides such as glucose (C₆H₁₂O₆).

What are the main functions of carbohydrates?

Provide short-term energy and structural support (cellulose in plants, glycogen in animals).

What is the 1st Law of Thermodynamics?

Energy cannot be created or destroyed—only transformed.

What is the 2nd Law of Thermodynamics?

Every energy transformation increases entropy (disorder).

Define free energy (ΔG).

Energy available to do work.

Define exergonic reaction.

Releases energy; spontaneous.

Define endergonic reaction.

Absorbs energy; non-spontaneous.

Define entropy (ΔS).

Measure of disorder.

Define enthalpy (ΔH).

Measure of heat or total energy in a system.

What is ATP and what does it do?

Adenosine Triphosphate; stores energy and drives endergonic reactions via phosphorylation.

How do enzymes speed up reactions?

By lowering activation energy and stabilizing transition states.

What factors increase enzyme activity?

Optimal temperature and higher enzyme concentration.

What factors decrease enzyme activity?

Extreme pH, high salt, or low temperature.

What is a competitive inhibitor?

Molecule that competes for the enzyme's active site.

What is a non-competitive inhibitor?

Molecule that binds elsewhere, changing enzyme shape and reducing activity.

Where does glycolysis occur and what are its products?

Cytoplasm; Glucose → Pyruvate + ATP + NADH.

Where does the Krebs cycle occur and what are its products?

Mitochondrial matrix; Pyruvate → CO₂ + NADH + FADH₂ + ATP.

Where does the electron transport chain (ETC) occur and what does it produce?

Inner mitochondrial membrane; uses O₂, NADH, FADH₂ → H₂O + ~34 ATP.

Define aerobic respiration.

Uses oxygen, occurs in mitochondria, yields ~36 ATP.

Define anaerobic respiration (fermentation).

No oxygen; occurs in cytoplasm, produces 2 ATP.

What happens during alcoholic fermentation?

Yeast converts pyruvate to ethanol + CO₂.

What happens during lactic acid fermentation?

Animals convert pyruvate to lactic acid (causes muscle fatigue).

Where do light-dependent reactions occur and what do they produce?

Thylakoid membrane; Light + H₂O → ATP + NADPH + O₂.

Where do light-independent reactions occur and what do they produce?

Stroma; CO₂ + ATP + NADPH → Glucose.

What energizes electrons in photosynthesis?

Light absorbed by Photosystems I and II.

What factors affect photosynthesis?

Temperature, light intensity, and oxygen levels.

How do C4 plants reduce photorespiration?

Store CO₂ in PEP and move it to bundle sheath cells.

How do CAM plants conserve water?

Take in CO₂ at night and store it for daytime use.

Why do C4 and CAM adaptations matter?

They prevent water loss and optimize CO₂ usage in hot/dry climates.

What is the final electron acceptor in respiration?

Oxygen (O₂).

What is the carbon source for glucose in photosynthesis?

Carbon dioxide (CO₂).

Compare NADH and NADPH.

NADH = used in respiration; NADPH = used in photosynthesis.

Compare ETC in mitochondria vs. chloroplasts.

Both use electron carriers and generate ATP, but differ in location and purpose.

What diagrams should you label for review?

Cellular respiration steps, chloroplast and mitochondrion structures.

What concepts should you be able to compare?

Respiration vs. Photosynthesis, Aerobic vs. Anaerobic, C4 vs. CAM.

What calculations should you practice?

ΔG (free energy), enzyme scenarios, ATP coupling examples.