Comprehensive Study Guide: Photosynthesis and Cellular Respiration

Vocabulary practice flashcards covering the biochemical mechanisms, organelle structures, pathways, and terminology of photosynthesis and cellular respiration.

Dry Mass Origin of Plants

The finding that the majority of added dry biomass in a growing tree originates from carbon dioxide ($\text{CO}_2$) absorbed from the air rather than soil nutrients or water.

Photosynthesis

An anabolic process performed by plants, algae, protists, and some bacteria that converts radiant solar energy into chemical energy stored in glucose, represented by the equation $6\text{CO}_2 + 6\text{H}_2\text{O} + \text{energy} \rightarrow \text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2$.

Chlorophyll a

The primary light-absorbing pigment directly involved in photosynthesis, absorbing light most effectively in the blue-violet and red regions of the visible spectrum.

Chlorophyll b

An accessory photosynthetic pigment that broadens the range of light wavelengths a plant can capture and transfer to chlorophyll a.

Carotenoids

Accessory plant pigments that absorb additional wavelengths of light and help protect plant cells against damage from excess solar radiation.

Leaf Coloration

The green appearance of leaves resulting from chlorophyll absorbing red and blue-violet wavelengths effectively while reflecting or transmitting unabsorbed green wavelengths.

Autumn Leaf Color Change

The seasonal process where cooler autumn temperatures cause plants to stop synthesizing chlorophyll and break down existing chlorophyll, unmasking underlying yellow, orange, red, and brown pigments.

Chloroplast

The double-membrane organelle found in plant and algal cells that serves as the site of photosynthesis.

Thylakoid

A flattened, disc-shaped membranous sac inside the chloroplast containing chlorophyll and accessory pigments, serving as the site of the light-dependent reactions.

Granum

A column or stack of disc-shaped thylakoids located inside the chloroplast (plural: grana).

Lamellae

Membranous channels or connective bridges that link adjacent grana stacks within the chloroplast stroma.

Stroma

The protein-rich, gel-like aqueous fluid surrounding the grana inside the chloroplast inner membrane, serving as the site of the light-independent reactions (Calvin cycle).

Thylakoid Lumen

The aqueous interior compartment enclosed by the thylakoid membrane where protons ($\text{H}^+$) accumulate to create a high-concentration electrochemical gradient.

Stomata

Microscopic pores on leaf surfaces that open and close to facilitate gas exchange, allowing $\text{CO}_2$ to diffuse in and $\text{O}_2$ to be released.

ATP (Adenosine Triphosphate)

A high-energy molecule synthesized during light-dependent reactions that supplies usable chemical energy to power cellular reactions, including the Calvin cycle.

NADPH (Nicotinamide Dinucleotide Phosphate)

A high-energy electron carrier formed when $\text{NADP}^+$ accepts two electrons ($2\,e^-$) and one proton ($\text{H}^+$), supplying reducing power to the Calvin cycle.

Oxidation

The loss of one or more electrons by an atom or molecule during a chemical reaction.

Reduction

The gain of one or more electrons by an atom or molecule during a chemical reaction.

Reducing Power

The chemical energy property of molecules in their reduced state that enables them to donate high-energy electrons to other substances.

Photolysis

The light-driven splitting of water in the thylakoid membrane represented by $2\text{H}_2\text{O} + \text{energy} \rightarrow 4\text{H}^+ + 4e^- + \text{O}_2$, replenishing electrons lost by photosystem II.

Photosystems (I and II)

Light-harvesting complexes embedded within the thylakoid membrane composed of chlorophyll and accessory pigments that excite electrons upon absorbing photons.

Photosynthetic Electron Transport Chain

A series of membrane-bound carrier molecules that transport excited electrons through the thylakoid membrane, using released energy to pump protons ($\text{H}^+$) from the stroma into the lumen.

ATP Synthase Complex

A specialized membrane enzyme channel that drives the phosphorylation of ADP to ATP as protons ($\text{H}^+$) passively diffuse down their concentration gradient from the lumen into the stroma.

Calvin Cycle

The light-independent cyclic pathway occurring in the chloroplast stroma that utilizes ATP and NADPH to convert $\text{CO}_2$ into G3P sugar and eventually glucose.

RuBisCO

Ribulose-1,5-bisphosphate carboxylase-oxygenase, the primary enzyme that catalyzes the initial carbon fixation step of the Calvin cycle by binding $\text{CO}_2$ to RuBP.

G3P (Glyceraldehyde-3-phosphate)

A three-carbon phosphorylated sugar produced during the reduction stage of the Calvin cycle used to regenerate RuBP and synthesize glucose.

Paper Chromatography

A laboratory analytical technique used to separate and identify leaf pigments based on their differential solubility in a solvent moving across chromatography paper.

$R_f$ Value (Reference Flow)

A numerical ratio calculated as $\frac{\text{distance travelled by pigment}}{\text{distance travelled by solvent}}$, where a lower value reflects lower pigment solubility in the chosen solvent.

Anabolic Pathway

A metabolic pathway that consumes energy to construct larger, complex molecules from smaller building blocks, exemplified by photosynthesis building glucose.

Catabolic Pathway

A metabolic pathway that releases energy by breaking down complex molecules into simpler compounds, exemplified by cellular respiration breaking down glucose into ATP.

Cellular Respiration

The catabolic process occurring in plants and animals that breaks down glucose in the presence of oxygen to produce ATP, carbon dioxide, and water.

Mitochondria

Double-membrane organelles present in eukaryotic cells that act as cellular powerhouses, hosting the primary energy-generating stages of cellular respiration.

Mitochondrial Matrix

The fluid interior enclosed by the inner mitochondrial membrane containing enzymes and an optimal pH to support the Krebs cycle.

Cristae

Extensive infoldings of the inner mitochondrial membrane that expand surface area for electron transport chains and ATP synthase enzymes.

Mitochondrial Intermembrane Space

The narrow compartment between the inner and outer mitochondrial membranes where protons are rapidly concentrated during electron transport.

Main Steps of Aerobic Cellular Respiration

The four sequential stages involved in breaking down glucose: 1. Glycolysis, 2. Pyruvate Oxidation, 3. Krebs Cycle, and 4. Electron Transport Chain and Chemiosmosis.