• BOX 24.1 Absorption Spectra of Respiratory Pigments

The Chemical Properties and Distributions of the Respiratory Pigments

• Hemoglobins contain heme and are the most widespread respiratory pigments
• Copper-based hemocyanins occur in many arthropods and molluscs
• BOX 24.2 Blood Cells and Their Production
• Chlorocruorins resemble hemoglobins and occur in certain annelids
• Iron-based hemerythrins do not contain heme and occur in three or four phyla

The O₂-Binding Characteristics of Respiratory Pigments

• Human O₂ transport provides an instructive case study
• A set of general principles helps elucidate O₂ transport by respiratory pigments
• The shape of the oxygen equilibrium curve depends on  O₂-binding site cooperativity
• Respiratory pigments exhibit a wide range of affinities for O₂
• The Bohr effect: Oxygen affinity depends on the partial pressure of CO₂ and the pH
• The Root effect: In unusual cases, CO₂ and pH dramatically affect the oxygen-carrying capacity of the respiratory pigment
• Thermal effects: Oxygen affinity depends on tissue temperature
• Organic modulators often exert chronic effects on oxygen affinity
• BOX 24.3 Resurrection of the Blood Hemoglobin of the Extinct Woolly Mammoth: Evidence for an Ancient Adaptation to the Challenges of Regional Hypothermia
• Inorganic ions may also act as modulators of respiratory pigments

The Functions of Respiratory Pigments in Animals

• Patterns of circulatory O₂ transport: The mammalian model is common but not universal
• BOX 24.4 Heme-Containing Globins in Intracellular Function: Myoglobin Regulatory and Protective Roles, Neuroglobins, and Cytoglobins
• Respiratory pigments within a single individual often display differences in O₂ affinity that aid successful O₂ transport
• Evolutionary adaptation: Respiratory pigments are molecules positioned directly at the interface between animal and environment
• The respiratory-pigment physiology of individuals undergoes acclimation and acclimatization
• Icefish live without hemoglobin
• BOX 24.5 Blood and Circulation in Mammals at High Altitude

Carbon Dioxide Transport

• The extent of bicarbonate formation depends on blood buffers
• Carbon dioxide transport is interpreted by use of carbon dioxide equilibrium curves
• The Haldane effect: The carbon dioxide equilibrium curve depends on blood oxygenation
• Critical details of vertebrate CO₂ transport depend on carbonic anhydrase and anion transporters

Acid–Base Physiology

• Acid–base regulation involves excretion or retention of chemical forms affecting H⁺ concentration
• Disturbances of acid–base regulation fall into respiratory and metabolic categories
• BOX 24.6 Acidification of Aquatic Habitats