Energy and Respiration Practice Flashcards

Vocabulary flashcards covering cellular energy, ATP structure and function, mitochondrial anatomy, types of phosphorylation, respiratory pathways, and respiratory substrates.

Active Transport

The movement of molecules across cell membranes against their concentration gradient, requiring energy supplied by ATP.

Sodium-Potassium Pump

A primary active transport mechanism that maintains cellular ion balance and resting membrane potential by pumping $3\,Na^+$ out of the cell and $2\,K^+$ into the cell.

Anabolic Reactions

Biosynthetic reactions that build complex molecules from simpler molecules (such as DNA and protein synthesis), requiring an input of energy.

Endothermic Organisms

Organisms, including mammals and birds, that generate heat internally through metabolic processes and employ physiological mechanisms to regulate body temperature.

Adenosine Triphosphate (ATP)

A phosphorylated nucleotide composed of adenine, ribose sugar, and three phosphate groups that serves as the central energy currency of cells.

Substrate-Level Phosphorylation

The direct transfer of a phosphate group from a phosphorylated substrate intermediate to ADP to form ATP during metabolic reactions in glycolysis and the Krebs cycle.

Oxidative Phosphorylation

The synthesis of ATP using energy released by electron transfer through the electron transport chain (ETC) to oxygen, which powers a proton gradient driving chemiosmosis via ATP synthase.

Photophosphorylation

The production of ATP using light energy during photosynthesis, taking place in the thylakoid membranes of chloroplasts.

Outer Mitochondrial Membrane

The smooth outer phospholipid membrane of a mitochondrion that contains porins and is relatively permeable to small molecules such as pyruvate and ADP.

Inner Mitochondrial Membrane

The folded inner phospholipid membrane of a mitochondrion that is relatively impermeable to $H^+$ ions and houses electron transport chain complexes and ATP synthase.

Mitochondrial Cristae

Infoldings of the inner mitochondrial membrane that significantly increase the surface area available for electron transport chains and ATP synthase complexes.

Mitochondrial Matrix

The aqueous interior compartment enclosed by the inner mitochondrial membrane containing link reaction and Krebs cycle enzymes, circular mitochondrial DNA, and 70S ribosomes.

ATP Synthase Complex

An enzyme embedded in the inner mitochondrial membrane that synthesises ATP from ADP and Pi as protons flow down their electrochemical gradient back into the matrix.

Respiratory Substrates

Organic molecules—primarily carbohydrates, lipids, and proteins—that can be oxidised during cellular respiration to release energy for ATP synthesis.

Deamination

The metabolic process in which the nitrogenous amino group is removed from an amino acid before its remaining carbon skeleton enters respiratory pathways.

Respiratory Quotient (RQ)

The volumetric or molar ratio of carbon dioxide produced to oxygen consumed during respiration: $\text{RQ} = \frac{\text{CO}_2 \text{ produced}}{\text{O}_2 \text{ consumed}}$.

Respirometer

An experimental apparatus used to measure respiration rate and determine RQ by measuring oxygen uptake while absorbing produced carbon dioxide with soda lime.

Nicotinamide Adenine Dinucleotide (NAD⁺)

A major hydrogen and electron acceptor coenzyme operating in glycolysis, the link reaction, and the Krebs cycle that is reduced to NADH for use in oxidative phosphorylation.

Flavin Adenine Dinucleotide (FAD)

A coenzyme operating primarily in the Krebs cycle that accepts hydrogen atoms and electrons to form reduced FADH₂, delivering electrons to the electron transport chain.

Coenzyme A (CoA)

A non-protein molecule that binds to the 2-carbon acetyl group formed during pyruvate oxidation, creating acetyl-CoA to transfer the group into the Krebs cycle.

Glycolysis

The oxygen-independent first stage of respiration taking place in the cytoplasm, converting 1 glucose molecule (6C) into 2 pyruvate molecules (3C) with a net yield of $2\,\text{ATP}$ and $2\,\text{NADH}$.

Link Reaction

The metabolic pathway in the mitochondrial matrix that links glycolysis to the Krebs cycle by decarboxylating and dehydrogenating pyruvate (3C) into acetyl-CoA (2C), releasing $\text{CO}_2$ and producing NADH.

Krebs Cycle

A cyclical series of reactions in the mitochondrial matrix that oxidises acetyl-CoA, producing $2\,\text{CO}_2$, $3\,\text{NADH}$, $1\,\text{FADH}_2$, and $1\,\text{ATP}$ per acetyl-CoA molecule.

Oxaloacetate

A 4-carbon molecule in the mitochondrial matrix that combines with 2-carbon acetyl-CoA to produce citrate (6C), initiating the Krebs cycle and regenerating at its completion.