Metabolism Test Review: Photosynthesis and Cellular Respiration

Comprehensive vocabulary flashcards covering the stages, chemical equations, cellular locations, redox reactions, pathways, adaptations, and inhibitors involved in photosynthesis and cellular respiration.

Photosynthesis

The process by which plants use the sun's energy to fix $CO_2$ into glucose within the chloroplast of the cell, summarized by the equation: $6CO_2 + H_2O + \text{sunlight} \rightarrow C_6H_{12}O_6 + 6O_2$.

Thylakoid

The chloroplast structure containing pigments like chlorophyll that absorb light energy to power chemical reactions for photosynthesis.

Stroma

The fluid-filled region of the chloroplast that uses the products of thylakoid reactions to finish photosynthesis and produce glucose.

OIL RIG

A mnemonic for redox reactions indicating that Oxidation Is Loss of electrons and Reduction Is Gain of electrons.

Photolysis

The light-driven splitting of water molecules occurring at Photosystem II (PSII) that releases electrons, protons ($H^+$), and $O_2$, causing the oxygen atom in $H_2O$ to go from an oxidation state of $-2$ to $0$.

Reduction of Carbon Dioxide

The process in the light-independent reactions (Calvin cycle) where stored energy in ATP and NADPH is used to build carbohydrates as $CO_2$ gains electrons, shifting carbon from an oxidation state of $+4$ down to $0$ in glucose.

Photosystem II (PSII)

The photosystem that functions first in the light-dependent reactions, taking in light and water to perform photolysis, creating ATP, and releasing electrons, oxygen, and protons.

Photosystem I (PSI)

The photosystem that functions second, taking in light, electrons from PSII/ETC, $H^+$, and $NADP^+$ to reduce $NADP^+$ into NADPH.

Plastocyanin

The carrier protein that transports electrons from the electron transport chain following PSII directly to PSI.

Calvin Cycle

A metabolic pathway located in the stroma of chloroplasts where carbon enters as $CO_2$ and exits as PGAL ($\frac{1}{2}$ glucose); requires $6$ molecules of $CO_2$ to produce $1$ molecule of glucose.

Carbon Fixation

The initial phase of the Calvin cycle where the enzyme RuBisCO attaches a $CO_2$ molecule to a $5$-carbon sugar (RuBP), quickly splitting into two $3$-carbon compounds (3-PGA).

Regeneration (Calvin Cycle)

The final phase of the Calvin cycle where remaining G3P molecules stay in the cycle and utilize ATP energy to rearrange back into RuBP.

Photorespiration

A wasteful process that occurs under high $O_2$ and low $CO_2$ ratios when stomata close in hot, dry conditions to reduce water loss, trapping oxygen inside the leaf.

C4 Plants

Plants such as corn and sugarcane that adapt to avoid photorespiration by physically separating carbon fixation and the Calvin cycle into different cells (bundle sheath cells).

CAM Plants

Plants such as cacti and pineapples that avoid photorespiration by separating carbon fixation and the Calvin cycle by time of day, running the Calvin cycle during daylight with closed stomata.

Pigment

A substance that captures solar energy to do work during photosynthesis; its perceived color corresponds to the wavelengths of light that are reflected rather than absorbed.

Absorption Spectrum

A graph showing pigment absorbance across light wavelengths; the reflected color corresponds to the low point of the curve (e.g., low absorbance around $\sim 500\,\text{nm}$ results in a green color when ends at $350\text{--}425\,\text{nm}$ and $700\,\text{nm}$ are high).

Cyanide

A mitochondrial poison that blocks Complex IV of the ETC, preventing electron transfer to oxygen and leaving NADH unable to oxidize to $NAD^+$, resulting in extremely high NADH and low $NAD^+$ levels.

2,4-Dinitrophenol (DNP)

A mitochondrial uncoupler that allows protons to bypass ATP synthase, crashing ATP synthesis, accelerating glycolysis and metabolic rates, and dissipating proton-motive energy as heat.

Glycolysis

An anaerobic process occurring in the cytosol that lyses $1$ glucose into $2$ pyruvate, consuming $2\,\text{ATP}$ to yield a gross of $4\,\text{ATP}$ (net gain of $2\,\text{ATP}$) and $2\,\text{NADH}$.

Pyruvate Oxidation

An aerobic transition reaction taking place in the mitochondrial matrix that converts $2$ pyruvate, $2\,NAD^+$, and $2\,\text{CoA}$ into $2\,\text{Acetyl-CoA}$, $2\,CO_2$, and $2\,\text{NADH}$.

Citric Acid Cycle

An aerobic stage in the mitochondrial matrix where $2\,\text{Acetyl-CoA}$, $6\,NAD^+$, $2\,\text{FAD}$, and $2\,\text{ADP} + P_i$ produce $4\,CO_2$, $6\,\text{NADH}$, $2\,\text{FADH}_2$, and $2\,\text{ATP}$.

Chemiosmosis

The step in oxidative phosphorylation where protons flow down their electrochemical concentration gradient from the intermembrane space back into the matrix through ATP synthase (Complex V) to produce ATP.

Kerrigan Tracker ATP Conversion Ratios

The theoretical conversion values in aerobic respiration where $1\,\text{NADH} = 3\,\text{ATP}$ ($10\,\text{NADH} = 30\,\text{ATP}$) and $1\,\text{FADH}_2 = 2\,\text{ATP}$ ($2\,\text{FADH}_2 = 4\,\text{ATP}$), yielding $34\,\text{ATP}$ from the ETC.

Lactic Acid Fermentation

An anaerobic pathway in animals and bacteria where pyruvate accepts electrons and protons from NADH to form lactic acid, regenerating $NAD^+$ to sustain glycolysis and produce a net of $2\,\text{ATP}$.

Alcoholic Fermentation

An anaerobic pathway in yeast and some plants where pyruvate loses a carbon as $CO_2$ to become acetaldehyde, which then accepts electrons from NADH to produce ethanol and regenerate $NAD^+$.