Respiration Pigments and Partial Pressures

Respiratory Pigment

protein that helps transport oxygen in the blood or body fluids of animals.

Haemoglobin

• protein composed of 4 polypeptide chains and haeme groups → contain 1 atom of Fe which binds to 1 molecule of oxygen

• this allows whole blood to carry more oxygen

• OXYGEN CARRIER AND RESPIRATORY PIGMENT!

• binds to oxygen coming from the alveoli forming oxyhaemoglobin, then eventually deoxyhaemoglobin once deoxygenated

Oxygen carriers in invertebrates

• haemocyanin

  • uses Cu as oxygen binding molecule

  • circulates in haemolymph of arthropods and some mollusks

Partial Pressure

• pressure of a single gas within a mixture of gases

Value of mmHg

760 - the atmosphere exerts a downward force equal to that of a column of mercury 760mm high

how to calculate partial pressure at sea level

conc of 760mmHg

21% () 760mmHg

.21 (760) = 159.1 mmgHG

Why does gas still diffuse if water is already at equilibrium with air

Even if water reaches equilibrium with air, blood is always moving and taking oxygen away. This keeps the oxygen level in the blood lower than in the air (or water), so oxygen keeps diffusing in.

Diffusion gradients of respiratory gases in mammals - how does this work (partial pressure wise)

• PO2 in the blood is lower than PO2 in the alveoli so O2 diffuses into the blood

• PCO2 however is higher in the blood than in the alveoli so diffuses across alveoli

• blood leaves pulmonary veins → po2 is raised, pco2 is lowered

• blood is then pumped around the body and diffuses through interstitial fluid O2 goes into cells and co2 moved into blood