Cellular Respiration and Energy Transformation

Vocabulary flashcards covering cellular respiration, ATP generation mechanisms, coenzymes, mitochondrial structure, ATP synthase subunits, and related pathologies.

Cyanide

A highly toxic chemical that inhibits cytochrome c oxidase (Complex IV) in the mitochondrial electron transport chain, blocking electron transport and causing ATP production through oxidative phosphorylation to decrease dramatically.

Cytochrome c oxidase (Complex IV)

An enzyme in the mitochondrial electron transport chain that normally transfers electrons to oxygen ($O_2$), the final electron acceptor in aerobic cellular respiration.

Histotoxic hypoxia

A condition in which cells cannot properly use oxygen even when oxygen is available, such as when cyanide prevents oxygen from receiving electrons at Complex IV.

Zyklon B

A substance that releases hydrogen cyanide, which was used by Nazi Germany to murder more than a million people in gas chambers at Auschwitz and other extermination camps.

Photosynthesis

A metabolic process occurring in chloroplasts of plants and algae and in certain photosynthetic bacteria that uses sunlight, carbon dioxide ($CO_2$), and water ($H_2O$) to produce glucose ($C_6H_{12}O_6$) and oxygen ($O_2$).

Cellular respiration

A series of chemical reactions that break down glucose ($C_6H_{12}O_6$) using oxygen ($O_2$) to produce ATP, releasing carbon dioxide ($CO_2$), water ($H_2O$), and heat.

Substrate-level phosphorylation

The production of ATP by directly transferring a phosphate group from a high-energy substrate molecule to ADP via an enzyme.

Substrate

A molecule that an enzyme acts upon during a chemical reaction.

Oxidative phosphorylation

The production of ATP using energy released from electrons moving through the electron transport chain (ETC) to power proton pumping and ATP synthase.

Coenzymes

Organic molecules that assist enzymes during chemical reactions, functioning as electron carriers that accept and donate electrons in redox reactions.

$NAD^+$ (Nicotinamide Adenine Dinucleotide)

The oxidized form of an electron carrier in cellular respiration that accepts 2 electrons ($e^-$) and 1 hydrogen ion ($H^+$) to become NADH.

NADH

The reduced form of $NAD^+$ that carries high-energy electrons and donates them to another molecule, returning to $NAD^+$.

FAD (Flavin Adenine Dinucleotide)

The oxidized form of an electron carrier in cellular respiration that accepts 2 electrons ($e^-$) and 2 hydrogen ions ($H^+$) to become $FADH_2$.

$$FADH_2$$

The reduced form of FAD that carries high-energy electrons and donates them to another molecule, returning to FAD.

NADPH (Nicotinamide Adenine Dinucleotide Phosphate)

The reduced form of the coenzyme $NADP^+$ that carries high-energy electrons and supplies electrons for anabolic reactions, including carbohydrate synthesis in the Calvin cycle.

ATP synthase

A protein complex located in the inner mitochondrial membrane that couples chemiosmosis with ATP production by using energy from the movement of $H^+$ ions down their electrochemical gradient.

$F_0$ subunit

The membrane-embedded portion of ATP synthase that forms a channel through which $H^+$ ions flow from the intermembrane space into the matrix, driving rotation.

$F_1$ subunit

The catalytic portion of ATP synthase located on the mitochondrial matrix side that uses rotational energy from the $F_0$ subunit to catalyze the synthesis of ATP from ADP and inorganic phosphate ($P_i$).

Sir Hans Krebs

The scientist who discovered the citric acid cycle by studying pigeon breast muscle tissue, whose paper was rejected by Nature in 1937 before being published in Enzymologia, and who received the 1953 Nobel Prize in Physiology or Medicine.

Mitochondria

Eukaryotic organelles with two membranes where pyruvate oxidation, the Krebs cycle, and oxidative phosphorylation take place; often called the powerhouse of the cell.

Cristae

Folds of the inner mitochondrial membrane that increase the surface area available for ATP production.

Intermembrane space

The compartment between the inner and outer mitochondrial membranes where $H^+$ ions accumulate during electron transport to establish a proton gradient.

Mitochondrial matrix

The internal space enclosed by the inner mitochondrial membrane that contains enzymes involved in pyruvate oxidation and the Krebs cycle.

Alzheimer's disease (AD)

A progressive neurological disease associated with neuronal damage, brain shrinkage, enlarged ventricles, and early mitochondrial dysfunction that impairs oxidative phosphorylation.

Amyloid-beta ($A\beta$) plaques

Abnormal accumulations of amyloid-beta protein that form in the brain and are associated with Alzheimer's disease.

Tau neurofibrillary tangles

Abnormal accumulations of tau protein that form inside neurons and are associated with Alzheimer's disease.