Cellular Respiration: every key term you need (+ practice quiz)
25 flashcard terms for General Biology I Topic 5, written to match the course framework. Study them here, then drill them as interactive flashcards, or test yourself with the 15-question quiz — free, no account needed.
The complete oxidation of glucose to carbon dioxide and water using oxygen as the final electron acceptor, capturing roughly a third of the released energy in the phosphate bonds of ATP.
Glycolysis
A ten-step cytosolic pathway splitting one six-carbon sugar into two three-carbon pyruvate molecules, with a net gain of two ATP and two reduced electron carriers, and no requirement for oxygen.
Energy investment phase
The first half of glycolysis, in which two ATP are spent to phosphorylate the sugar twice. Adding charged groups traps the sugar in the cell and destabilizes it for cleavage.
Energy payoff phase
The second half of glycolysis, in which each three-carbon fragment is oxidized and yields two ATP, so four are made and two are returned as net gain per starting sugar.
Substrate level phosphorylation
Direct transfer of a phosphate group from a high-energy substrate to a nucleotide diphosphate by an enzyme. It supplies the ATP of glycolysis and one nucleotide triphosphate per turn of the citric acid cycle.
Phosphofructokinase
The main control point of glycolysis, an allosteric enzyme inhibited by abundant ATP and by citrate and stimulated by adenosine monophosphate, so flux tracks the cell's actual energy deficit.
Pyruvate oxidation
The link step in the mitochondrial matrix where each pyruvate loses one carbon as carbon dioxide, is oxidized to an acetyl group, and is attached to coenzyme A while reducing one carrier.
Acetyl coenzyme A
The two-carbon entry molecule of the citric acid cycle, formed from sugars, fatty acids and some amino acids. Its thioester bond is high energy, which drives condensation with the four-carbon acceptor.
Citric acid cycle
A matrix pathway that fully oxidizes an acetyl group, releasing two carbon dioxides and per turn producing three reduced dinucleotide carriers, one flavin carrier and one nucleotide triphosphate.
Oxaloacetate
The four-carbon acceptor regenerated at the end of each cycle turn. Because it is reused catalytically, depleting it, as happens when intermediates are drained for biosynthesis, stalls the whole cycle.
Flavin adenine dinucleotide
An electron carrier reduced during one cycle step and bound within the enzyme complex that feeds electrons into the chain past the first pumping site, which is why it yields less ATP.
Electron transport chain
A series of membrane complexes and mobile carriers of steadily increasing electron affinity, arranged so electrons fall stepwise from reduced carriers to oxygen while energy is tapped in usable increments.
Ubiquinone
A small hydrophobic carrier that diffuses within the inner membrane, collecting electrons from two different entry complexes and delivering them onward. Its mobility lets separate entry points converge.
Cytochrome c
A small heme-containing protein on the outer face of the inner membrane that shuttles single electrons between complexes. Its release into the cytosol also triggers programmed cell death.
Proton motive force
The electrochemical gradient generated by pumping protons out of the matrix, combining a pH difference with a membrane voltage. It stores the energy that will drive phosphorylation.
Chemiosmosis
Mitchell's proposal, initially resisted, that electron transport and ATP synthesis are linked not by a chemical intermediate but by a proton gradient across a sealed membrane.
ATP synthase
A rotary motor enzyme in which returning protons spin a rotor, and the resulting conformational cycle in the catalytic head releases newly formed ATP. It converts a gradient into chemical bonds.
Oxidative phosphorylation
ATP production powered by the proton gradient rather than by direct phosphate transfer from a substrate. It accounts for the large majority of ATP made during aerobic respiration.
Oxygen as terminal acceptor
The final electron sink of the chain, combining with electrons and protons to make water. Without it electrons back up, carriers stay reduced, and the entire chain and cycle halt.
Respiration ATP yield
About 30 to 32 ATP per glucose in most eukaryotic cells. The value is a range rather than a fixed number because gradients also power transport and shuttle costs differ between tissues.
Uncoupling agent
A compound that carries protons back across the inner membrane without passing through the synthase. Electron transport speeds up, no ATP is made from the leak, and the energy appears as heat.
Brown adipose thermogenesis
Deliberate uncoupling in specialized fat tissue, where a membrane protein short-circuits the gradient so that oxidation of fat warms the animal instead of producing ATP.
Anaerobic fermentation
A cytosolic strategy for regenerating oxidized electron carriers without oxygen so glycolysis can continue. It yields no additional ATP beyond the two from glycolysis itself.
Lactate fermentation
The route in which pyruvate itself accepts the electrons and becomes lactate, restoring the oxidized carrier. It supports brief intense muscle effort, and the lactate is later reoxidized.
Alcoholic fermentation
The yeast route in which pyruvate loses a carbon as carbon dioxide and the resulting two-carbon compound is reduced to ethanol, regenerating the carrier and releasing the gas that leavens bread.