Cellular Respiration and Photosynthesis

Vocabulary flashcards covering the biochemical pathways of cellular respiration (aerobic and anaerobic fermentation), leaf and chloroplast structures, light properties, pigments, and photosynthesis stages.

Glycolysis

The first step of cellular respiration that breaks down glucose into pyruvate, requiring $NAD^+$ as an input and generating a net gain of $2\,\text{ATP}$.

Glycerol

A three-carbon breakdown product of fats that is converted into pyruvate before entering the respiration pathway.

Lactic Acid Fermentation

An anaerobic pathway occurring in animal muscles and certain bacteria where pyruvate is reduced to lactic acid (or lactate) while $NADH$ is oxidized back to $NAD^+$.

Alcohol Fermentation

An anaerobic pathway performed by yeast in which pyruvic acid is converted into the two-carbon molecule acetaldehyde, releasing $CO_2$, and acetaldehyde is subsequently reduced while $NADH$ is oxidized to $NAD^+$.

Acetaldehyde

A two-carbon molecule formed in alcohol fermentation when enzymes remove a carboxyl group from pyruvic acid, releasing $CO_2$.

Oxygen (in Aerobic Respiration)

The final electron acceptor in the electron transport chain required for aerobic cellular respiration to generate up to $38$ molecules of $\text{ATP}$ per glucose.

NADPH

The high-energy electron carrier utilized in the chloroplast during photosynthesis, functioning analogously to $NADH$ and $FADH_2$ in mitochondria.

Wavelength

The physical distance from one wave crest to another along the electromagnetic spectrum, inversely related to the amount of energy carried.

Photon

A discrete packet of light energy that can strike an electron in an atom's shell and boost it to an excited state.

Excited State

An unstable, high-energy condition of an electron after absorbing a photon, from which it can either return to its ground state releasing heat and fluorescence or be captured in a redox reaction.

Palisade Mesophyll

The upper tissue layer within a leaf where cells are organized standing upright on their short ends to capture incoming light.

Spongy Mesophyll

The haphazardly arranged lower leaf tissue layer containing abundant air spaces that acts functionally like a lung for gas exchange.

Stomata

Openings on the surface of a leaf analogous to nostrils that regulate gas exchange and can close to prevent water loss.

Guard Cells

Specialized cells flanking leaf stomata that swell and close the pore during hot or dry conditions to retain water.

Thylakoid Membranes

Specialized, interconnected internal membranes within the chloroplast where light is captured and light-dependent reactions occur.

Granum

A stack of thylakoid membranes inside the chloroplast.

Stroma

The fluid-filled area surrounding the thylakoids inside the chloroplast where glucose is synthesized.

Chlorophyll a

A primary photosynthetic pigment possessing a methyl group ($-CH_3$) that absorbs red and blue light while reflecting a blue-green color.

Chlorophyll b

An accessory photosynthetic pigment possessing a $-CHO$ group that gives it a light or olive-green appearance.

Phycoerythrin

A photosynthetic pigment found in deep aquatic plants or shaded understory plants that captures available light not absorbed by upper-level foliage.

Absorption Spectrum

A graphical representation showing the specific wavelengths of light absorbed by an individual pigment molecule.

Action Spectrum

A graph that integrates the light absorption profiles of multiple pigments to demonstrate the overall biological effectiveness of different wavelengths in driving photosynthesis.

Light-Dependent Reactions

The first stage of photosynthesis where light energy is absorbed, electrons are stripped, and $\text{ATP}$ is generated.

Light-Independent Reactions

The second stage of photosynthesis that utilizes $\text{ATP}$ and high-energy electrons from the light reactions to fix $CO_2$ into glucose.