Unit 3 Study Guide: Cellular Energetics and Photosynthesis

First Law of Thermodynamics

Energy cannot be created or destroyed, only transformed.

Second Law of Thermodynamics

Every energy transfer increases the entropy of the universe.

Catabolic Pathways

Metabolic pathways that break down complex molecules into simpler compounds, releasing energy.

Anabolic Pathways

Metabolic pathways that build complex molecules from simpler ones, consuming energy.

Exergonic Reaction

A reaction with a net release of free energy (ΔG < 0).

Endergonic Reaction

A reaction that absorbs free energy from its surroundings (ΔG > 0).

Energy Coupling

Using an exergonic process to drive an endergonic one.

ATP (Adenosine Triphosphate)

The primary molecule that cells use to manage their energy resources.

Hydrolysis of ATP

The process of breaking the terminal phosphate bond in ATP, releasing energy.

Phosphorylation

The transfer of a phosphate group to a molecule, increasing its reactivity.

Photosynthesis

The process that converts solar energy into chemical energy in the form of glucose and oxygen.

Chemical Equation of Photosynthesis

6CO2 + 6H2O + Light Energy → C6H12O6 + 6O2.

G3P (Glyceraldehyde 3-phosphate)

The direct product of the Calvin Cycle in photosynthesis.

Chloroplast

The organelle in eukaryotes where photosynthesis occurs.

Thylakoids

Sac-like photosynthetic membranes where the Light-Dependent Reactions occur.

Grana

Stacks of thylakoids in chloroplasts.

Stroma

The dense fluid outside the thylakoids where the Calvin Cycle occurs.

Photosystems

Reaction-center complexes in chloroplasts involved in capturing light energy.

Photosystem II (PSII)

Absorbs light best at 680 nm and functions first in the light reactions.

Photosystem I (PSI)

Absorbs light best at 700 nm and functions second in the light reactions.

Electron Transport Chain (ETC)

A series of proteins that transfer electrons from PSII to PSI, generating ATP.

NADPH Production

The formation of NADPH from NADP+ and electrons during photosynthesis.

Chemiosmosis

The movement of protons across a membrane to produce ATP.

Photophosphorylation

The process of generating ATP in photosynthesis via proton flow through ATP synthase.

Calvin Cycle

The process that uses ATP and NADPH to convert CO2 into sugar (G3P).

Carbon Fixation

The first step of the Calvin Cycle where CO2 is attached to RuBP.

Rubisco

The enzyme that catalyzes the first step of carbon fixation in photosynthesis.

Regeneration of RuBP

The final step of the Calvin Cycle where G3P molecules are rearranged to form RuBP.