Bioenergetics and Oxidative Metabolism

This set of vocabulary flashcards covers the principles of bioenergetics, mitochondrial structure, the electron transport chain (ETC) complexes, metabolic shuttles, and uncoupling proteins as detailed in the Chapter 9 lecture notes.

Bioenergetics

A branch of biochemistry focused on how cells transform, produce, store, and consume energy.

Avogadro's Number

The number of units from any substance in one mole, equal to $6.02 \times 10^{23}$.

Creatine Synthesis

A process occurring in the kidneys using three amino acids (including glycine and arginine) to produce a compound that is 95% stored in muscle and 5% in organs.

Creatine Phosphate

Functions as a storehouse for high-energy phosphate, donating a phosphate to ADP to replenish ATP in rapidly contracting muscle.

Creatinine

A waste product generated by the use of creatine phosphate which is subsequently excreted in urine.

Aerobic Metabolism oxidation yield

The complete oxidation of each pyruvate to $H_2O$ and $CO_2$ yields 2 moles of $CO_2$, 3 moles of NADH, 1 mole of $FADH_2$, and 1 mole of GTP.

Lactic Acid

The end product of anaerobic metabolism produced when pyruvate does not enter the mitochondria; it can restore $NAD^+$ levels and slows down skeletal muscle contraction.

Lactic Acid Threshold

The point reached between $50-80\%$ $VO_2$ max (maximal oxygen uptake) where lactic acid begins to accumulate.

Basal Metabolic Rate (BMR)

The total heat energy released from the body at rest, approximately $1800\,kcal/day$ for adult men ($70\,kg$) and $1300\,kcal/day$ for adult women.

Food Energy Conservation

$40\%$ of food energy is conserved as ATP, while the remaining $60\%$ is liberated as heat.

Metabolic Fuel Caloric Values

Fats = $9\,kcal/gram$, Carbohydrates = $4\,kcal/gram$, Proteins = $4\,kcal/gram$, and Alcohol = $7\,kcal/gram$.

TOM (translocase)

The transport protein located in the outer mitochondrial membrane used to transport large mitochondrial proteins synthesized from nuclear DNA.

mtDNA

Maternally inherited genome that encodes 13 viral subunits of the proton pumps and ATP synthase.

Complex I

Also known as NADH-Q reductase or NADH dehydrogenase; it oxidizes NADH, contains FMN, and pumps 4 protons from the matrix into the intermembranous space.

Glycerol phosphate shuttle

A mechanism used by skeletal muscle to enter the mitochondria by converting NADH to $FADH_2$ via the enzyme glycerol-3-phosphate-Q reductase (G).

Malate-aspartate shuttle

A mechanism used by the heart and liver to maintain NADH levels for the electron transport chain using the enzyme AST (SGOT).

Complex II

Also known as succinate-Q reductase or succinate dehydrogenase; it anchors the Kreb's cycle to the Inner Mitochondrial Membrane (IMM) and reduces FAD to $FADH_2$.

Fatty acyl CoA dehydrogenase (F)

The enzyme that catalyzes the first step of mitochondrial beta oxidation of fatty acids, reducing FAD to $FADH_2$.

Ubiquinone

Also known as Coenzyme Q10; a small, lipid-soluble electron acceptor that transfers electrons from Complexes I, II, G, and F to Complex III.

Complex III

Also known as Ubiquinone-Cytochrome c reductase; it transfers electrons to Cytochrome c and pumps 4 protons into the intermembranous space.

Cytochrome c

A small heme protein loosely bound to the outer surface of the inner membrane that shuttles electrons from Complex III to Complex IV; its release into the cytosol can induce apoptosis.

Complex IV

Also known as Cytochrome c oxidase; it contains copper, uses Cytochrome a and $a_3$, transfers electrons to oxygen to form water, and pumps 4 protons.

Chemiosmotic hypothesis

The theory that a proton gradient created by Complexes I, III, and IV creates electrochemical potential which drives ATP synthesis via ATP synthase (Proton motive force).

P:O ratios

A measure of high-energy phosphates synthesized per atom of oxygen consumed; the ratio is ~$2.5$ for NADH and ~$1.5$ for $FADH_2$.

Uncoupling proteins (UCP)

Inner membrane components that allow protons to leak, reducing ATP production and generating heat; UCP1 (thermogenin) is specifically found in brown adipose tissue.

UCP2

An uncoupling protein expressed ubiquitously; strong evidence suggests its synthesis in pancreatic $\beta$ cells is linked to Type II diabetes in obesity.

ETC Inhibitors

Chemicals that stop electron flow: Complex I is inhibited by Rotenone, Complex III by Antimycin A, and Complex IV by CO (carbon monoxide) and cyanide.

ADP-ATP translocase

The enzyme that allows the transport of ATP out of the mitochondria and ADP into the mitochondria from the cytoplasm.