Photosynthesis and Chemiosmosis Vocabulary Flashcards

Vocabulary flashcards covering photosynthetic pigments, photolysis, light-dependent and light-independent reactions, cyclic and non-cyclic photophosphorylation, and chemiosmosis based on lecture notes.

Photosynthesis

The transformation of light energy into chemical energy, represented by the chemical equation $6\text{CO}_2 + 6\text{H}_2\text{O} \rightarrow \text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2$, which is needed for the majority of life processes in the ecosystem.

Photolysis

The splitting of water molecules using light energy into electrons ($e^-$), hydrogen ions ($\text{H}^+$) used for the proton gradient, and oxygen ($\text{O}_2$) released into the atmosphere as a by-product.

Chromatography

A laboratory technique used to identify photosynthetic pigments by calculating an $R_f$ value using the ratio $R_f = \frac{\text{Solvent distance}}{\text{solute distance}}$.

Photosynthetic Pigments

Molecules such as chlorophyll a, chlorophyll b, and carotenoids that absorb light energy and convert it into chemical energy during photosynthesis, reflecting green light wavelengths.

Absorption Spectra

A graph showing the amount of light energy absorbed by different photosynthetic pigments across wavelengths ($400\,nm$ to $700\,nm$), characterized by peaks in the blue and red regions and low activity in the green region.

Action Spectra

A graph plotting the rate of photosynthesis against light wavelengths ($400\,nm$ to $700\,nm$), showing that wavelengths absorbed the most (blue and red) drive the highest rate of photosynthesis.

Antenna Complex

A pigment-protein cluster containing chlorophyll and accessory pigments (carotenoids, xanthophylls) that captures photons of light energy and transfers the energy to the reaction center.

Reaction Center

The region of a photosystem containing a special chlorophyll pair that receives transferred energy from the antenna complex and releases excited electrons ($e^-$) to the electron transport chain ($\text{ETC}$).

Photosystem I (PSI)

A pigment-protein complex located in the stroma lamellae containing a P700 special chlorophyll pair that receives light energy to re-excite electrons for reducing $\text{NADP}^+$ to NADPH, and does not undergo photolysis.

Photosystem II (PSII)

A pigment-protein complex located in the grana containing a P680 special chlorophyll pair that undergoes photolysis to replace excited electrons lost to the electron transport chain.

P680

The special chlorophyll pair located in the reaction center of Photosystem II (PSII).

P700

The special chlorophyll pair located in the reaction center of Photosystem I (PSI).

Array of Pigments

A collection of chlorophylls and accessory pigments that increases photon absorption and light-capturing capacity, ensuring all captured energy reaches the special chlorophyll pair (P680 or P700).

Light-Dependent Reaction

The photosynthetic process occurring in the thylakoid where photons excite electrons, photolysis splits water, electron carriers activate proton pumps to build a thylakoid lumen proton gradient, and ATP and NADPH are generated.

Light-Independent Reaction (Calvin Cycle)

The photosynthetic process occurring in the chloroplast stroma where carbon fixation, reduction, and regeneration of ribulose bisphosphate take place to produce glucose.

Rubisco

The enzyme that catalyzes the carbon fixation stage of the Calvin cycle by combining carbon dioxide ($\text{CO}_2$) with ribulose bisphosphate.

Ribulose Bisphosphate (RuBP)

A $5\text{-carbon}$ molecule ($\text{P-}(5\text{C})\text{-P}$) that binds with $\text{CO}_2$ via Rubisco to form an unstable $6\text{-carbon}$ intermediate during carbon fixation.

Glycerate-3-phosphate

A $3\text{-carbon}$ molecule ($\text{P-}(3\text{C})$) produced when the unstable $6\text{-carbon}$ intermediate breaks down in the Calvin cycle, which is subsequently reduced using ATP and NADPH.

Triose Phosphate

The $3\text{-carbon}$ end product ($\text{P-}(3\text{C})$) of the reduction phase in the Calvin cycle; $\frac{1}{6}$ of its carbon goes toward glucose production, while $\frac{5}{6}$ regenerates ribulose bisphosphate.

Non-Cyclic Photophosphorylation

The standard light-dependent pathway where electrons excited at PSII flow down the $\text{ETC}$ to PSI to reduce $\text{NADP}^+$ to NADPH, generating ATP and releasing oxygen ($\text{O}_2$) via photolysis.

Cyclic Photophosphorylation

A light-dependent pathway occurring when electrons cannot be used to form NADPH, causing excited electrons from PSI to cycle back to the proton pump to continuously generate ATP without producing NADPH or oxygen.

Photosynthesis Chemiosmosis

The mechanism in the thylakoid membrane where electron movement along the $\text{ETC}$ pumps protons ($\text{H}^+$) from the stroma into the thylakoid lumen, and their diffusion back to the stroma through ATP synthase catalyzes ADP to ATP.

Respiration Chemiosmosis

The mechanism in the mitochondrial cristae membrane where electron movement along the $\text{ETC}$ pumps protons ($\text{H}^+$) from the matrix into the intermembrane space, and their diffusion back to the matrix through ATP synthase catalyzes ADP to ATP.