Module 2 - Unit 1: Respiration and ATP Biochemistry

Flashcards covering vocabulary terms, key definitions, and chemical mechanisms from Module 2 Unit 1 lecture notes on Respiration and ATP.

ATP (Adenosine Triphosphate)

An energy-rich molecule composed of adenine, ribose sugar, and three phosphate groups, serving as the immediate short-term energy store driving cellular metabolism.

ADP (Adenosine Diphosphate)

A nucleotide composed of adenine, ribose sugar, and two phosphate groups that combines with inorganic phosphate ($P_i$) and energy to synthesise ATP.

Phosphorylation

The chemical process of adding a phosphate group to an organic molecule.

ATPase

The enzyme that catalyses the hydrolysis of ATP into ADP and inorganic phosphate ($P_i$), releasing energy.

Photophosphorylation

The synthesis of ATP using light energy, occurring during the light-dependent stage of photosynthesis in chlorophyll.

Oxidative Phosphorylation

The production of ATP coupled with electron transport along the electron transport chain in the presence of oxygen during aerobic respiration.

Glycolysis

The first stage of respiration taking place in the cytoplasm, involving the breakdown of a 6-carbon glucose molecule into two 3-carbon pyruvate molecules without requiring oxygen.

Triose Phosphate

A 3-carbon intermediate sugar produced in glycolysis when 6-carbon fructose bisphosphate is split.

Substrate-level Phosphorylation

The direct formation of ATP by transferring a phosphate group from an intermediate compound directly to ADP, occurring in glycolysis and the Krebs cycle.

NAD (Nicotinamide Adenine Dinucleotide)

A coenzyme and hydrogen carrier that accepts hydrogen atoms removed during dehydrogenation reactions, becoming reduced NAD ($NADH$).

FAD (Flavin Adenine Dinucleotide)

A coenzyme and hydrogen carrier in the Krebs cycle that accepts hydrogen atoms to form reduced FAD ($FADH_2$).

Dehydrogenase

An enzyme that catalyses dehydrogenation, removing hydrogen atoms from a substrate molecule.

Dehydrogenation

The chemical removal of hydrogen atoms from a molecule.

Decarboxylation

The removal of a carbon dioxide molecule ($CO_2$) from a compound.

Oxidation

A chemical reaction involving the loss of hydrogen atoms or electrons, or the gain of oxygen atoms, resulting in a release of energy.

Reduction

A chemical reaction involving the gain of hydrogen atoms or electrons, or the loss of oxygen atoms, accompanied by a gain of energy.

Link Reaction

The reaction in the mitochondrial matrix where pyruvate is converted into 2-carbon acetyl coenzyme A through decarboxylation and dehydrogenation in the presence of oxygen.

Krebs Cycle

A cyclic sequence of oxidation-reduction reactions in the mitochondrial matrix that breaks down acetyl groups to generate reduced NAD, reduced FAD, ATP, and $CO_2$.

Citrate

A 6-carbon acid compound formed in the Krebs cycle when 2-carbon acetyl CoA combines with 4-carbon oxaloacetate.

Oxoglutarate

A 5-carbon acid intermediate in the Krebs cycle produced by the decarboxylation and dehydrogenation of 6-carbon citrate.

Oxaloacetate

A 4-carbon acid compound in the mitochondrial matrix that accepts the 2-carbon acetyl group from acetyl CoA to regenerate citrate in the Krebs cycle.

Electron Transport Chain (ETC)

A series of electron carriers arranged by decreasing potential energy on the inner mitochondrial membrane, converting energy from hydrogen atoms into ATP.

Cytochromes

Electron carrier proteins in the electron transport chain that transfer electrons successively toward cytochrome oxidase.

Cytochrome Oxidase

The terminal enzyme of the electron transport chain that catalyses the combination of electrons, protons ($H^+$), and molecular oxygen to produce water.

Cristae

The highly folded structures of the inner mitochondrial membrane that increase surface area for the attachment of enzymes and coenzymes involved in oxidative phosphorylation.

Anaerobic Respiration

The incomplete breakdown of respiratory substrates without oxygen in the cytoplasm, yielding a net total of 2 ATP per glucose molecule.

Lactate Dehydrogenase

The enzyme in animal skeletal muscle that converts pyruvate into lactate during anaerobic respiration to regenerate oxidised NAD.

Oxygen Debt

The additional oxygen required after strenuous exercise to metabolise accumulated lactate in the liver, re-oxygenate oxymyoglobin, and resynthesise depleted ATP.

Obligate Anaerobes

Organisms that can survive and respire only in the complete absence of oxygen.

Alcohol Dehydrogenase

The enzyme in plant tissues and fungi that catalyses the conversion of pyruvate into ethanol and $CO_2$ during anaerobic respiration.

Respiratory Quotient (RQ)

The ratio calculated by dividing the volume of carbon dioxide released by the volume of oxygen consumed during respiration: $\text{RQ} = \frac{\text{Volume of } CO_2 \text{ released}}{\text{Volume of } O_2 \text{ consumed}}$.

Respirometer

An experimental apparatus used to measure the rate of respiration by recording changes in gas volumes corresponding to oxygen consumption or carbon dioxide release.

Thermobarometer

A control boiling tube in a respirometer setup that compensates for external changes in temperature and atmospheric pressure.

Methylene Blue

A redox indicator dye that acts as an artificial hydrogen acceptor, changing from blue to colourless when reduced.

2,3,5-triphenyl tetrazolium chloride (TTC)

A redox indicator solution that acts as a hydrogen acceptor, turning from colourless to pink upon reduction.