Metabolic Processes: Cellular Respiration, Photosynthesis, and the Calvin Cycle

Comprehensive vocabulary flashcards covering the biochemical pathways of cellular respiration, fermentation, photosynthesis, organelle comparisons, and Melvin Calvin's carbon-fixation experiments.

Beta-oxidation

The metabolic process of breaking down fatty acids into two-carbon acetyl-CoA molecules that enter the mitochondria.

Deamination

The removal of the nitrogen-containing amino group from amino acids, which is subsequently processed into waste.

Gluconeogenesis

The process of producing glucose from non-carbohydrate sources—including lactate, glycerol, and certain amino acids—to maintain blood glucose levels.

Phosphofructokinase (PFK)

An enzyme in glycolysis that converts fructose-6-phosphate into fructose-1,6-bisphosphate; it is inhibited by high $ATP$ and activated by high $AMP$ or $ADP$.

Allosteric Inhibition

The regulation of enzyme activity that occurs when an effector molecule binds to a site other than the active site, altering the enzyme's shape and decreasing its catalytic activity.

Anaerobic Respiration

A cellular respiration pathway that functions without $O_2$, utilizing an electron transport chain with alternative terminal electron acceptors such as nitrate ($NO_3^-$), sulfate ($SO_4^{2-}$), or iron(III) ($Fe^{3+}$).

Lactic Acid Fermentation

An anaerobic pathway occurring in animals, bacteria, and fungi where $NADH$ transfers electrons to pyruvate to yield lactate, regenerating $NAD^+$ so glycolysis can continue.

Alcohol Fermentation

An anaerobic pathway in yeast and some bacteria where pyruvate is decarboxylated to acetaldehyde (releasing $CO_2$) and subsequently reduced to ethanol, oxidizing $NADH$ to $NAD^+$ and yielding a net of $2\,\text{ATP}$.

Photosystem II (PS II)

A thylakoid protein complex that absorbs light to supply electrons to the electron transport chain and relies on the Z-enzyme to split water to replace lost electrons.

Photosystem I (PS I)

A photosynthetic multiprotein complex in the thylakoid membrane that uses light energy to re-energize electrons received from the electron transport chain.

Ferredoxin

A protein that transfers high-energy electrons from Photosystem I to catalyze the reduction of $NADP^+$ into $NADPH$.

Rubisco

The carbon-fixing enzyme located in the chloroplast stroma that attaches inorganic $CO_2$ to ribulose bisphosphate ($\text{RuBP}$).

RuBP (Ribulose 1,5-bisphosphate)

A five-carbon molecule located in the stroma that serves as the initial carbon dioxide ($CO_2$) acceptor during the Calvin cycle.

Calvin Cycle (Synthesis Stage)

The light-independent stage of photosynthesis occurring in the stroma that consumes $ATP$ and $NADPH$ to fix $CO_2$ into G3P; requiring $6\,\text{turns}$ ($6\,CO_2$, $18\,\text{ATP}$, and $12\,NADPH$) to produce $1$ complete glucose molecule.

Cristae

The foldings of the inner mitochondrial membrane that house electron transport chains and $ATP$ synthase for aerobic cellular respiration.

Thylakoids

The internal membrane-bound flattened sacs within chloroplasts where light absorption and the light-dependent reactions of photosynthesis take place.

Radioactive Carbon-14 ($^{14}\text{C}$)

A radioactive isotope used by Melvin Calvin to label carbon dioxide ($CO_2$), enabling the tracking of carbon atoms through the sequence of photosynthetic reactions in algae.

Chromatography (in Calvin's Experiments)

A separation technique utilized by Melvin Calvin to isolate and identify intermediate chemical compounds containing radioactive carbon-14 at varied exposure intervals.

3-Phosphoglycerate (PGA)

The initial intermediate formed after carbon fixation in the Calvin cycle; it is detected on chromatograms alongside other sugar phosphates (such as fructose phosphate) before the formation of $\text{RuBP}$.