Cellular Respiration and Photosynthesis

Comprehensive vocabulary flashcards covering aerobic and anaerobic cellular respiration pathways, fuel sources, light physics, photosynthetic pigments, leaf and chloroplast anatomy, and the stages of photosynthesis.

Aerobic Respiration

A staged universal metabolic process requiring oxygen that extracts energy from glucose and other fuels, yielding approximately $36\text{--}38\text{ ATP}$ per glucose molecule.

Glycolysis

The first step of cellular respiration occurring in the cytoplasm that breaks down glucose into pyruvate and produces a net gain of $2\text{ ATP}$.

Oxygen (in Aerobic Respiration)

The final electron acceptor in the electron transport chain; without it, electron flow stops, causing the electron transport chain, Krebs cycle, and link reaction to halt.

Alternative Fuel Entry into Respiration

The universal mechanism whereby starches break into glucose, fructose feeds directly into glycolysis, maltose is split apart, lactose/galactose convert to glucose, glycerol converts to pyruvate, and fatty acids convert to acetyl groups.

Lactic Acid Fermentation

An anaerobic pathway occurring in oxygen-deprived animal muscles and certain bacteria where pyruvate is reduced to lactic acid, oxidizing $NADH$ to $NAD^+$ and producing only $2\text{ ATP}$.

NAD+ Regeneration

The critical biochemical role of fermentation that re-oxidizes $NADH$ back into $NAD^+$, allowing glycolysis to continue generating ATP when oxygen is unavailable.

Acidophilus

A bacterium used in yogurt production that ferments lactose into lactic acid, lowering milk pH from approximately $6.6$ to $4.4$ to create a sour taste.

Alcohol Fermentation

An anaerobic process in yeast where pyruvate is converted to acetaldehyde and $CO_2$, after which acetaldehyde is reduced to ethanol while oxidizing $NADH$ to $NAD^+$.

Photosynthesis

The reverse redox process of cellular respiration that uses light energy to synthesize glucose and oxygen from carbon dioxide and water: $6CO_2 + 6H_2O + \text{Light Energy} \rightarrow \text{Glucose} + 6O_2$.

NADPH

The specialized high-energy electron carrier utilized within the chloroplast during photosynthesis, contrasting with the $NADH$ and $FADH_2$ used in cellular respiration.

Visible Light Spectrum

The segment of the electromagnetic spectrum spanning approximately $450\text{--}700\text{ nm}$ (ROYGBIV), ranging from red (longest wavelength, lowest energy) to violet (shortest wavelength, highest energy).

Photon

A discrete packet of light energy that excites an electron in a photosynthetic pigment, raising it temporarily from a ground state to a higher energy level.

Chlorophyll a

A primary photosynthetic pigment featuring a $-\text{CH}_3$ (methyl) group that absorbs red and blue light and reflects green light, appearing blue-green.

Chlorophyll b

An accessory photosynthetic pigment featuring a $-\text{CHO}$ group that absorbs red and blue light and reflects green light, appearing olive or light green.

Carotenoids (Beta-carotene)

Accessory plant pigments that absorb light in the blue range and reflect orange wavelengths.

Phycoerythrin

An accessory pigment found in shaded understory plants and deep aquatic plants that absorbs remaining wavelengths of light except high-energy and red light.

Absorption Spectrum

A graph illustrating the specific wavelengths of light absorbed by a single, individual pigment.

Action Spectrum

A graph that integrates the absorption profiles of multiple pigments to demonstrate the overall rate of photosynthesis across different wavelengths.

Engelmann's Experiment

A historical experiment using Spirogyra, a prism, and bacteria to demonstrate that oxygen-seeking bacteria cluster predominantly at the red and blue ends of the visible spectrum where chlorophyll activity is highest.

Palisade Mesophyll

The top layer of mesophyll cells in a leaf standing vertically on their short ends to maximize light absorption.

Spongy Mesophyll

The loosely arranged lower layer of leaf cells characterized by extensive air spaces that facilitate gas exchange like a lung.

Stomata

Microscopic openings on the surface of a leaf (analogous to nostrils) that regulate gas exchange and water release.

Guard Cells

Specialized cells bordering stomata that swell to close the pores in hot, dry conditions, preventing water loss.

Thylakoid Membranes

Interconnected internal membranes within the chloroplast containing pigments; they serve as the site where light is captured and electrons are stripped.

Grana

Stacks of disc-shaped thylakoid membranes located inside the chloroplast.

Stroma

The fluid-filled space surrounding the thylakoid membranes inside the chloroplast where glucose is synthesized.

Light-Dependent Reactions

The first stage of photosynthesis occurring on thylakoid membranes that captures light, splits water, strips electrons, and generates $ATP$, $NADPH$, and $O_2$.

Light-Independent Reactions (Calvin Cycle)

The second stage of photosynthesis occurring in the stroma that uses stored $ATP$ and $NADPH$ along with $CO_2$ to assemble glucose, capable of running during the day or at night.