Enzymes and Cellular Respiration

Vocabulary flashcards covering enzyme function, factors affecting enzyme activity, anaerobic fermentation pathways, and the stages of aerobic cellular respiration including glycolysis, pyruvate oxidation, the electron transport chain, and oxidative phosphorylation.

Enzymes

Biological catalysts, mostly proteins with names often ending in -ase, that speed up the rate of a reaction without being consumed.

Activation Energy

The energetic "hill" that reactants must overcome; enzymes lower this energy during induced fit by stressing covalent bonds.

Enzyme Cofactors

Adjuncts that assist enzyme activity, including inorganic minerals such as Cu, Zn, and Fe, as well as organic vitamins or coenzymes.

Competitive Inhibitors

Inhibitors that restrict enzyme activity, with examples including DDT and penicillin.

Fermentation

An older anaerobic pathway living things use to make or regenerate ATP, dating back to when early Earth lacked oxygen and was populated mainly by anaerobic bacteria.

Alcohol Fermentation

An anaerobic process occurring in bacteria and yeasts where glucose undergoes glycolysis to produce 2 pyruvates, which are broken down into 2 ethanols, 2 $CO_2$, and 2 ATP.

Lactic Acid Fermentation

An anaerobic process in fungi, bacteria, muscles, and liver where glucose via glycolysis yields 2 pyruvates that produce 2 lactates (or lactic acids) and 2 ATP, without producing $CO_2$.

Obligate Anaerobes

Organisms that must live in the absence of oxygen, such as the bacterium Clostridium tetani.

Facultative Anaerobes

Organisms, such as some yeasts, that can live either with or without oxygen.

Aerobic Cellular Respiration

A catabolic, exergonic redox reaction ($C_6H_{12}O_6 + 6O_2 \rightarrow 6H_2O + 6CO_2 + 686\text{ kcals}$) where glucose is oxidized and oxygen is reduced to regenerate ATP efficiently in the mitochondria (except glycolysis).

$NAD^+$ (Nicotinamide Adenine Dinucleotide)

A coenzyme electron acceptor that accepts 2 electrons and 2 $H^+$ from glucose with the help of the enzyme dehydrogenase.

NADH

The reduced form of $NAD^+$ that acts as an electron carrier/transporter, carrying 2 electrons (energy) and 1 $H^+$ (proton) to the electron transport chain.

Electron Transport Chain (ETC)

A series of protein electron carriers located on the mitochondrial cristae, each progressively more electronegative, releasing energy in a gradual "cool burn" to regenerate ATP.

Ubiquinone (Co Q 10 / "Q")

A specific named protein member of the electron transport chain on the mitochondrial cristae.

Chemiosmosis

The diffusion process where $H^+$ ions actively pumped into the intermembrane space diffuse back across the inner membrane through ATP Synthase via the Proton Motive Force.

Oxidative Phosphorylation

The combined process of the electron transport chain and chemiosmosis on the inner mitochondrial membrane cristae where oxygen plays a key terminal role in regenerating ATP from ADP.

ATP Synthase

A transport protein functioning as a molecular mill or motor (consisting of a rotor, stator, rod, and catalytic knob) that generates 26–28 out of 30–32 ATPs during cellular respiration.

Glycolysis

A 10-step sugar-splitting process occurring in the cytoplasm that breaks down glucose into 2 pyruvate molecules, 2 ATP, and 2 NADH via substrate-level phosphorylation.

Substrate-Level Phosphorylation

The generation of ATP by the direct removal and transfer of phosphate groups from organic compounds, as seen in glycolysis.

Pyruvate Oxidation

The mitochondrial active transport process catalyzed by pyruvate dehydrogenase in which pyruvates are oxidized to Acetyl Coenzyme A, producing 2 NADH and releasing $CO_2$ for the first time.