Cellular Respiration and Photosynthesis

Comprehensive vocabulary flashcards covering the biochemical pathways, cellular structures, equations, and molecular yields of aerobic cellular respiration, anaerobic fermentation, and photosynthesis.

Aerobic Cell Respiration

The cellular process of breaking down glucose in the presence of oxygen to synthesize $ATP$, represented by the equation $C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + \text{Energy stored in ATP}$.

Mitochondria

The eukaryotic organelles where the majority of aerobic cellular respiration occurs, consisting of an outer membrane, inner membrane, cristae, inter-membrane space, and matrix.

Cellular Uses of ATP

Activities powered by $ATP$ including active transport, synthesis of macromolecules, driving cell growth and repair, electrical energy (in both plants and animals), and muscle movement (in animals only).

Glycolysis

The first stage of cellular respiration occurring in the cytoplasm, where one molecule of glucose is split into two molecules of pyruvate.

Energy Investment Stage

The initial phase of glycolysis where $2$ phosphate groups are added to glucose via the breakdown of $2\text{ ATP}$ into $2\text{ ADP}$, causing the molecule to split in half.

Energy Payoff Stage

The second phase of glycolysis in which $4\text{ ATP}$ are generated, $2\text{ NADH}$ high-power electron carrier molecules are produced, and $2$ molecules of pyruvate are formed.

Oxidation of Pyruvate

The second stage of cellular respiration taking place in the mitochondrial matrix, where a carbon and oxygen are removed from each pyruvate to produce Acetyl-CoA, $NADH$, and $CO_2$.

Net Yield of Pyruvate Oxidation

The net molecules produced from the oxidation of two pyruvates per glucose: $2\text{ Acetyl-CoA}$, $2\text{ NADH}$, and $2\text{ CO}_2$.

Krebs Cycle (Citric Acid Cycle)

The third stage of cellular respiration occurring in the mitochondrial matrix, in which Acetyl-CoA is processed through cyclical reactions to generate $ATP$ and electron carriers.

Citric Acid

The $6$-carbon molecule formed in the first step of the Krebs cycle when a $2$-carbon acetyl group joins a $4$-carbon starting molecule.

Net Yield of the Krebs Cycle

The total molecules produced per glucose molecule ($2$ turns of the cycle): $2\text{ ATP}$, $6\text{ NADH}$, $2\text{ FADH}$, and $4\text{ CO}_2$.

Electron Transport Chain (ETC)

The fourth stage of cellular respiration located on the mitochondrial inner membrane where electrons from $NADH$ and $FADH$ move across proteins to produce the majority of cellular $ATP$.

Final Electron Acceptor

Oxygen ($O_2$), which accepts electrons at the end of the electron transport chain and combines with protons to produce water ($H_2O$).

Chemiosmosis (Cellular Respiration)

The process wherein protons ($H^+$) accumulate in high concentration in the intermembrane space and pass through $ATP$ synthase down their concentration gradient into the matrix to synthesize $ATP$.

Aerobic Respiration ATP Yield

A theoretical maximum yield of $38\text{ ATP}$ per $1$ glucose molecule, based on each $NADH$ yielding $3\text{ ATP}$ and each $FADH$ yielding $2\text{ ATP}$.

Anaerobic Respiration (Fermentation)

A metabolic process that generates $ATP$ in the absence of oxygen; in humans, it occurs in the form of lactic acid fermentation.

Lactic Acid Fermentation

An anaerobic process where pyruvate is converted to lactic acid to oxidize $NADH$ back to $NAD^+$, replenishing the $NAD^+$ necessary to maintain glycolysis and producing a net of $2\text{ ATP}$ per glucose.

Autotrophs

Organisms such as plants and algae that carry out photosynthesis to synthesize their own glucose from inorganic compounds.

Heterotrophs

Organisms that cannot make their own food or utilize carbon dioxide directly and must consume organic material for their carbon source.

Leaf

The primary photosynthetic organ of a plant, composed of specialized cells densely packed with chloroplasts.

Chloroplast

The double-membrane organelle containing thylakoids and stroma where both stages of photosynthesis occur.

Thylakoid

A membrane-bound, disc-like structure within the chloroplast that houses chlorophyll pigments and serves as the site for light-dependent reactions.

Granum

A stack of thylakoid discs inside the chloroplast.

Stroma

The fluid-filled space within the chloroplast surrounding the thylakoid membranes where the Calvin cycle takes place.

Chlorophyll

Specialized pigment molecules located in thylakoid membranes that absorb blue and red light while reflecting green light.

Visible Light Spectrum for Plants

The radiation wavelengths ranging from $400\text{ nm}$ to $700\text{ nm}$ absorbed by plants to drive photosynthesis.

Stomata

Microscopic pores on the underside of plant leaves that open and close to permit $CO_2$ to enter and allow $O_2$ and $H_2O$ to exit.

Light Dependent Reactions

Photosynthetic reactions that take place on the thylakoid membrane during daylight to convert solar energy into chemical energy stored in $ATP$ and $NADPH$.

Photosystems

Protein complexes embedded in the thylakoid membrane containing chlorophyll pigments that capture light energy and release excited electrons to the electron transport chain.

Photolysis of Water

The enzymatic splitting of $H_2O$ at Photosystem II that produces oxygen ($O_2$), protons ($H^+$) inside the thylakoid lumen, and electrons to replace those lost by chlorophyll.

Chemiosmosis (Photosynthesis)

The diffusion of protons ($H^+$) from high concentration in the thylakoid lumen through $ATP$ synthase into the stroma, driving the phosphorylation of $ADP$ into $ATP$.

Calvin Cycle

The light-independent stage of photosynthesis occurring in the stroma that utilizes atmospheric $CO_2$, $ATP$, and $NADPH$ to synthesize glucose.

Carbon Fixation

Step 1 of the Calvin cycle, where carbon from $CO_2$ is bonded onto an $RuBP$ molecule catalyzed by the enzyme RUBISCO to form $6$ molecules of $PGA$.

RUBISCO

RuBP Carboxylase, the enzyme in the stroma that catalyzes the fixation of carbon dioxide onto ribulose 1,5-bisphosphate.

RuBP

Ribulose 1,5-bisphosphate, a $5$-carbon starting molecule that accepts $CO_2$ in carbon fixation and is continuously regenerated during the Calvin cycle.

PGA

Phosphoglycerate, the $3$-carbon acid formed following carbon fixation that is reduced to $G3P$ using $ATP$ and $NADPH$.

G3P

Glyceraldehyde 3-phosphate, a $3$-carbon sugar produced in the Calvin cycle; one molecule exits per turn to combine with a second $G3P$ to form a single glucose molecule.

RuBP Regeneration

Step 3 of the Calvin cycle, where the $5$ remaining $G3P$ molecules are chemically rearranged back into $3$ molecules of $RuBP$ using $ATP$.