Cellular Respiration and ATP Cycle Vocabulary

A comprehensive vocabulary set covering the primary terminology, stages, components, and chemical processes of cellular respiration and the ATP-ADP cycle based on the lecture notes.

Sir Hans Adolf Krebs

The scientist who discovered the citric acid cycle pathway in cellular respiration, winning the Nobel Prize for his work.

Aerobic Respiration

Cellular respiration that takes place in the presence of oxygen gas to produce energy, water ($\text{H}_2\text{O}$), and carbon dioxide ($\text{CO}_2$) from food.

Anaerobic Respiration

Cellular respiration that takes place in the absence of oxygen gas to obtain energy by breaking down glucose into end products like lactic acid or ethanol.

Fermentation

A natural process through which microorganisms like yeast and bacteria convert carbohydrates such as starch and sugar into alcohol or acids in the absence of oxygen.

Alcoholic Fermentation

A biological process converting sugars like glucose, fructose, and sucrose into cellular energy, producing ethanol ($\text{C}_2\text{H}_5\text{OH}$) and carbon dioxide ($\text{CO}_2$) as by-products.

Lactic Acid Fermentation

An anaerobic metabolic reaction occurring in some bacteria and animal muscle cells where glucose or six-carbon sugars are converted into cellular energy and lactate ($\text{C}_3\text{H}_6\text{O}_3$).

Glycolysis

A $10\text{-step}$ enzymatic reaction sequence in the cytoplasm that converts a six-carbon glucose molecule ($\text{C}_6\text{H}_{12}\text{O}_6$) into two three-carbon pyruvate molecules ($\text{CH}_3\text{COCOOH}$), resulting in a net gain of $2\,ATP$ and $2\,NADH$.

Pyruvate Oxidation

A stage of cellular respiration in the mitochondrial matrix where each pyruvate is transformed into a two-carbon acetyl CoA molecule, emitting carbon dioxide ($\text{CO}_2$) and producing $NADH$.

Citric Acid Cycle

An $8\text{-step}$ cycle in the mitochondrial matrix, also known as the Krebs cycle or TCA cycle, that oxidizes acetyl-CoA to release stored energy, producing carbon dioxide ($\text{CO}_2$), $NADH$, $FADH_2$, and $ATP$ or $GTP$.

Oxidative Phosphorylation

A process in the mitochondria consisting of the electron transport chain and chemiosmosis that utilizes high-energy electrons from $NADH$ and $FADH_2$ to generate the majority of cellular $ATP$.

Mitochondria

Cellular organelles that serve as the sites of cellular respiration, using oxygen to drive the generation of $ATP$ by extracting energy from sugars, fats, and other fuels.

Cristae

Highly folded structures of the inner mitochondrial membrane that increase the surface area to volume ratio for electron transport and oxidative phosphorylation.

Mitochondrial Matrix

The innermost compartment of mitochondria containing appropriate enzymes and a suitable pH for pyruvate oxidation and the Krebs cycle.

Intermembrane Space

The small space between the inner and outer mitochondrial membranes where hydrogen ions ($\text{H}^+$) quickly accumulate to establish a proton gradient.

Outer Mitochondrial Membrane

The outer membrane boundary of the mitochondrion containing transport proteins for shuttling pyruvate from the cytoplasm into the mitochondrial matrix.

Acetyl CoA

A two-carbon molecule linked to Coenzyme A produced from carbohydrates, proteins, or lipids before entering the Krebs cycle.

Oxaloacetate

A four-carbon acceptor molecule in the mitochondrial matrix that combines with a two-carbon acetyl group from acetyl-CoA to produce citrate.

Citrate

A six-carbon compound formed in the first step of the Krebs cycle when acetyl-CoA transfers an acetyl group to oxaloacetate.

Electron Transport Chain

A series of carrier protein complexes and enzymes embedded in the inner mitochondrial membrane that transfer electrons down energy levels to pump protons ($\text{H}^+$) and create a gradient.

Chemiosmosis

The process where protons ($\text{H}^+$) diffuse down their established electrochemical gradient through ATP synthase across the inner mitochondrial membrane to drive ATP synthesis.

Peter Mitchell

The scientist who proposed the Chemiosmotic Theory in the 1960s, establishing that electron transport and ATP synthesis are coupled across an inner mitochondrial membrane proton gradient.

ATP Synthase

An enzyme complex in the inner mitochondrial membrane that harnesses potential energy from a flowing hydrogen ion ($\text{H}^+$) gradient to combine ADP and an inorganic phosphate group to produce ATP.

Electrochemical Gradient

A gradient produced by ion concentration and charge differences across a membrane that determines the directional flow of ions through open channels.

Adenosine Triphosphate (ATP)

The primary energy transfer molecule in cells, composed of a nitrogenous base (adenine), a sugar (ribose), and three phosphate groups linked by high-energy bonds.

Adenosine Diphosphate (ADP)

A lower energy molecule composed of adenine, ribose, and two phosphate groups that is formed when ATP releases a phosphate group and energy into the cytoplasm.

Exergonic Reaction

An energy-releasing chemical reaction, exemplified by the removal of a phosphate group from ATP to form ADP and free energy for cellular processes.

Endergonic Reaction

An energy-requiring chemical reaction, exemplified by attaching a free phosphate group to ADP using energy from food breakdown to synthesize ATP.