Ch 13Respiration and Energy Transfer — Class 11 Biology, concept-first.

Maintenance of life requires a continuous supply of energy, and respiration is the process that fulfils this continuous need.

Cellular respiration occurs in two distinct forms - anaerobic and aerobic. Anaerobic respiration, also called fermentation, is cellular respiration that does not involve atmospheric oxygen at all.

Glycolysis (from the Greek glykys, sweet, and lysis, splitting) is the enzymatic breakdown of one 6-carbon glucose molecule into two 3-carbon pyruvic acid molecules.

When oxygen is not available quickly enough, the NADH+H⁺ produced during glycolysis must still be re-oxidised back to NAD⁺ so that glycolysis can keep running - and cells do this by handing that hydro…

Aerobic respiration involves molecular oxygen in the oxidation of glucose, and unlike anaerobic respiration it oxidises glucose completely.

The conversion of pyruvic acid to acetyl CoA is an oxidative decarboxylation reaction, catalysed by a multienzyme complex called the pyruvate dehydrogenase complex (PDH), present in the mitochondria o…

Pyruvic acid's 2-carbon acetyl fragment (as acetyl-CoA) is completely oxidised in the mitochondrial matrix through the Krebs cycle - also called the TCA (tricarboxylic acid) cycle or citric acid cycle…

Wherever NADH+H⁺ and FADH₂ are produced - during glycolysis, the connecting-link reaction, and the Krebs cycle - they are ultimately re-oxidised with the help of a series of electron carriers and enzy…

Both anaerobic and aerobic respiration are carried out through many small steps rather than as one single reaction, and this stepwise design serves several distinct purposes:

The respiratory quotient (RQ), or respiratory ratio, is the ratio of the volume of CO₂ released to the volume of O₂ consumed during respiration: RQ = (Volume of CO₂ released) / (Volume of O₂ consumed)

Bringing the chapter's themes together, respiration matters to the organism in several distinct ways: