BCM 1.6: Metabolism, Energy Metabolism, Oxidative Phosphorylation

Vocabulary flashcards generated from Module 4 lecture notes covering metabolic pathways, enzyme regulation, energy calculations, calorimetry, cellular respiration, electron transport chain complexes, and oxidative phosphorylation mechanisms.

Metabolism

A series of highly integrated networks of enzyme-catalyzed reactions divided into anabolic, catabolic, and amphibolic pathways.

Anabolic Pathways

Metabolic pathways involved in the synthesis of biological compounds, accompanied by the utilization of energy (e.g., conversion of ATP to ADP).

Catabolic Pathways

Metabolic pathways involved in oxidative processes, accompanied by the liberation of energy that is utilized in anabolic reactions.

Amphibolic Pathways

Metabolic pathways that act as links between anabolic and catabolic pathways, such as the Krebs Cycle.

Committed Step

An irreversible reaction unique to a metabolic pathway that proceeds with a large loss of free energy and ensures the pathway's directionality.

Rate-Limiting Step

The slowest step in any reaction mechanism process that limits the rate at which the overall metabolic pathway occurs.

Substrate Channeling

A mechanism in which several enzyme active sites are linked by a channel through which intermediate molecules pass directly without diffusing into the bulk solvent.

Enzyme Turnover

A process involving the synthesis and degradation of enzyme proteins, serving as a form of genetic control over enzyme amount.

Enzyme Multiplicity

A regulatory mechanism where distinct enzymes act on a single substrate, with each enzyme generating different products (e.g., Aspartokinase I, II, III).

Cumulative Feedback Regulation

A form of feedback control, also called concerted inhibition, commonly found in branched pathways where each end product inhibits the committed step, causing greater overall inhibition together than individually.

Energy Charge

An index of the cellular energy status ranging from $0$ (all AMP) to $1$ (all ATP), calculated as $\text{Energy Charge} = \frac{[\text{ATP}] + \frac{1}{2}[\text{ADP}]}{[\text{ATP}] + [\text{ADP}] + [\text{AMP}]}$.

Calorie

The standard unit for measuring energy, defined as the amount of heat energy required to raise the temperature of $1\text{ mL}$ of water by $1^\text{C}$.

Metabolic Equivalent (MET)

A measure of energy expenditure defined as the energy value of one liter of oxygen consumed, equivalent to $4.825\text{ kcal}$ (or $5\text{ kcal/L}$).

Respiratory Quotient (RQ)

The ratio of carbon dioxide produced to oxygen consumed over a given period, calculated as $\text{RQ} = \frac{\text{moles }\text{CO}_2\text{ expired}}{\text{moles }\text{O}_2\text{ consumed}}$.

Bomb Calorimeter

An apparatus used to determine the total heat energy available from food in vitro by measuring its heat of combustion.

Basal Metabolic Rate (BMR)

The rate of energy expenditure measured with the body at complete physical and mental rest, relaxed but not asleep, several hours after strenuous activity, and in a thermoneutral environment.

Modified Tanhauser's Method

A formula used to calculate desirable body weight (DBW) in kilograms: $\text{DBW (kg)} = [\text{Height (cm)} - 100] - [10\times 10^{-2} \times (\text{Height (cm)} - 100)]$.

Thermic Effect of Food (TEF)

The energy expended by the body to digest, absorb, and metabolize ingested food, typically accounting for about $10\text{ }\text{\%}$ of the sum of BEE and activity increment.

Adenosine Triphosphate (ATP)

A nucleotide and anhydride of phosphoric acid composed of adenine, ribose, and three phosphate groups, serving as the principal energy currency of the cell.

Substrate Level Phosphorylation

The direct synthesis of ATP from ADP and inorganic phosphate coupled to the direct cleavage of high-energy bonds in metabolic intermediates, independent of the electron transport chain.

Oxidative Phosphorylation

The synthesis of ATP coupled to the transfer of electrons from reduced coenzymes ($\text{NADH}$ and $\text{FADH}_2$) to oxygen via the electron transport chain in the inner mitochondrial membrane.

Cardiolipin

A unique diphosphatidylglycerol lipid concentrated in the inner mitochondrial membrane that maintains membrane impermeability to protons and structurally stabilizes respiratory supercomplexes.

Complex I (NADH Dehydrogenase)

A multiprotein complex in the inner mitochondrial membrane that oxidizes $\text{NADH}$ to $\text{NAD}^+$, passes electrons through FMN and Fe-S centers to Coenzyme Q, and pumps $4\text{ H}^+$ into the intermembrane space.

Complex II (Succinate Dehydrogenase)

An inner mitochondrial membrane complex that converts $\text{FADH}_2$ to $\text{FAD}^+$ during succinate oxidation and transfers electrons directly to Coenzyme Q without pumping protons.

Complex III (Cytochrome bc1 Complex)

A respiratory complex that transfers electrons from ubiquinol to cytochrome c via the Q-cycle and translocates $4\text{ H}^+$ into the intermembrane space.

Complex IV (Cytochrome c Oxidase)

The terminal complex of the ETC containing heme $a/a_3$ and binuclear copper centers that catalyzes the four-electron reduction of molecular oxygen to water and translocates $2\text{ H}^+$ into the intermembrane space.

Complex V (ATP Synthase)

A molecular rotary motor enzyme consisting of $F_0$ and $F_1$ functional units that synthesizes ATP from ADP and inorganic phosphate as protons flow down their electrochemical gradient.

Chemiosmotic Coupling Hypothesis

The hypothesis proposed by Peter Mitchell (1961) stating that electron transport generates an electrochemical proton gradient across the inner mitochondrial membrane that drives ATP synthesis.

Binding Change Mechanism

The rotational model proposed by Paul Boyer (1964) in which proton flux causes rotation of the \text{\gamma} subunit, driving sequential conformational changes (Open, Loose, Tight) in the three \text{\beta} subunits of ATP Synthase.

Oligomycin

An inhibitor of phosphorylation that binds to the stalk protein on the $F_0$ fraction of ATP Synthase, plugging the proton channel and preventing ATP synthesis.

Bongkrekik Acid

A toxin produced by Pseudomonas species in bongkrek that inhibits the adenine nucleotide translocase carrying ADP and ATP across the inner mitochondrial membrane.

2,4-Dinitrophenol (DNP)

A classic uncoupler of oxidative phosphorylation that dissipates the proton gradient across the inner mitochondrial membrane, allowing substrate oxidation to proceed without ATP synthesis while releasing energy as heat.