Photosynthesis, Cellular Energy, and Thermodynamics

Vocabulary practice flashcards covering coupled reactions, ATP, photosynthetic pigments, light-dependent and independent reactions (Calvin Cycle), thermodynamics, and the electron transport chain based on the lecture notes.

Jan

Recognized as the 'Father of Photosynthesis'.

Fritz Lipmann

Recognized as the 'Father of the ATP Cycle'.

Exergonic Reaction

A chemical reaction that releases energy by breaking chemical bonds of a large reactant, producing smaller products.

Endergonic Reaction

A chemical reaction that absorbs energy by forming chemical bonds from smaller reactants to produce a larger product.

Coupled Reaction

A process occurring when an endergonic reaction is powered by an exergonic reaction, such as photosynthesis.

Phosphorylation

The process in which ATP transfers a phosphate group to another molecule, carried out by enzymes to power energy-requiring cellular activities.

Chlorophyll A

The primary photosynthetic pigment (molecular formula $C_{55}H_{72}O_5N_4$) with a blue-green reflecting color that absorbs light in the orange, violet, blue, and red spectrums.

Chlorophyll B

An accessory photosynthetic pigment (molecular formula $C_{55}H_{70}O_6N_4Mg$) with a yellow-greenish reflecting color that collects energy from blue and yellow light and transfers it to Chlorophyll A.

Carotenoids

Bright yellow, red, and orange accessory pigments in plants, algae, and photosynthetic bacteria that absorb light in the blue to green and violet regions.

Xanthophyll

Yellow photosynthetic accessory pigments that contain oxygen.

Carotene

Orange photosynthetic accessory pigments that do not contain oxygen.

Phycobilins

Water-soluble accessory pigments found in red algae and cyanobacteria that absorb green to red wavelengths of light.

Phycoerythrin

A red protein pigment complex that functions as an accessory to the main chlorophyll pigments.

Phycocyanin

A blue-colored pigment-protein complex belonging to the light-harvesting phycobiliprotein family.

Deyanda Flint

Author cited in 2017 regarding the function of photosynthetic pigments absorbing light energy and exciting free electrons to higher energy levels.

Robert Hill and Fay Bendall

Scientists who proposed the widely accepted photoelectron transfer mechanism in 1960 involving light reaction I and light reaction II.

Light-Dependent Reactions

The 'photo' stage of photosynthesis taking place in the thylakoids, converting solar energy into potential energy stored in ATP and NADPH while releasing $O_2$.

Light-Independent Reactions

The 'synthesis' stage of photosynthesis (Calvin Cycle) taking place in the stroma of chloroplasts, using ATP and NADPH from light dependent reactions to synthesize carbohydrates.

Antenna Complex

The light-receiving array in a photosystem consisting of chlorophyll a, chlorophyll b, and accessory pigments bound to pigment-binding proteins.

Reaction Center

The central component of a photosystem surrounded by an antenna complex, containing a pair of chlorophyll a molecules, proteins, and a primary electron acceptor.

Photosystem I (PSI)

A photosystem with a reaction center consisting of P700, a pair of chlorophyll a molecules with an absorption peak at $700\,nm$.

Photosystem II (PSII)

A photosystem with a reaction center consisting of P680, a pair of chlorophyll a molecules with an absorption peak at $680\,nm$.

Non-Cyclic Photophosphorylation

The standard light-dependent electron pathway occurring in the thylakoid membrane involving both PSII and PSI, requiring water oxidation and generating both ATP and NADPH.

Cyclic Photophosphorylation

An electron flow route occurring on the stroma lamella or fret channels involving only PSI, recycling electrons down a cyclic path to produce ATP only.

Pheophytin

A highly modified chlorophyll molecule that serves as the primary electron acceptor in Photosystem II.

Ferredoxin

A highly modified chlorophyll molecule that serves as the primary electron acceptor in Photosystem I.

Photolysis of Water

The enzyme-driven oxidation of water ($H_2O$) in PSII, splitting it into two hydrogen ions, electrons, and an oxygen atom.

Resonance

The transfer process within the antenna complex where energy is passed from one pigment molecule to another until reaching the reaction center.

Oxidation

The chemical process in which a molecule loses one or more electrons.

Melvin Calvin

Scientist who discovered the dark reactions/light-independent cycle with his associates, receiving the Nobel Prize in 1961.

Carbon Fixation Phase

The initial step of the Calvin Cycle where carbon dioxide ($CO_2$) binds to RuBP sugar facilitated by the enzyme Rubisco, splitting into 3-PGA.

Reduction Phase

The second step of the Calvin Cycle where 3-PGA is converted into G3P using energy supplied by ATP and NADPH.

Carbohydrate Formation Phase

The third step of the Calvin Cycle where G3P molecules are converted into carbohydrates or sugars.

Regeneration Phase

The fourth step of the Calvin Cycle where G3P and ATP are utilized to regenerate RuBP to start the cycle again.

Thermodynamics

The study of energy and energy transfer involving physical matter.

First Law of Thermodynamics

Also known as the Law of Conservation of Energy, it states that energy cannot be created or destroyed in an isolated system.

Second Law of Thermodynamics

States that the entropy of any isolated system always increases over time.

Third Law of Thermodynamics

States that the entropy of a system approaches a constant value as temperature approaches absolute zero.

Thermodynamic System

The matter and its environment relevant to a specific case of energy transfer.

Thermodynamic Surroundings

Everything located outside of a designated thermodynamic system.

Electron Transport Chain (ETC)

A series of membrane-embedded protein complexes that couple redox reactions to shuttle electrons and pump protons across a membrane to produce ATP via chemiosmosis.