H/C Physiology O2 and Co2 Part II

structure and function of hemoglobin

One hemoglobin can carry up to four molecules of oxygen. (iron-based) pigment; transports oxygen and CO2 to and from tissues; shape allows blood circulation because the shape is able to get through small, narrow entryways

Most oxygen is transported by Hb (about 95%) by binding with it and forming oxyhemoglobin; this is the main way of oxygen transport because, if we used diffusion and release of normal O2 into blood, it would cause bubbles to form, which would block blood flow into arteries/vents, and also because O2 is nonpolar, which water is polar, so diffusion isn’t great

sigmoid oxygen equilibrium curve of hemoglobin and consequences for loading and unloading of oxygen.

• P50: PP of O2 in the blood when the Hb is 50% saturated with O2

• As more oxygen molecules are bound, affinity for oxygen increases, which makes an S-shaped curve

  • Curve of P(O2) (in mmHg) vs hemoglobin O2 saturation (%)

• Affinity usually found at 50% on y-axis; higher affinity is farther left (needs less oxygen in blood for it to meet a red cell and bind

how the CO2 equilibrium curve differs from that of oxygen

• 5-10% of CO2 is diluted in plasma, ~20% is carbaminohemoglobin, and ~70-75% is bicarbonate

• CO2 out of cell: produced in cell metabolism -> by partial pressure, enters red cell -> binds with water to create carbonic acid, making blood more acidic -> released as bicarbonate, which binds to hemoglobin -> new ion (Cl) needs to enter cell to balance charge by creating gradient for carbonic acid to leave -> carbonic acid must leave cell to maintain blood pH

• CO2 into alveoli: Cl leaves, HCO3 enters -> forms carbonic acid -> forms CO2 and H2O -> CO2 and H2O are free inside cell

• PROCESS: breathing in O2, which binds to Hb -> O releases Hb and enters cell -> CO2 from cells come back into red blood cells, some binds to hemoglobin, other forms carbonic acid H2CO3 and leaves cell because it converts into H (which binds to hemoglobin) and HCO3^- and brings it out of the cell, brings Cl in to create gradient/balance charge -> 

• Carbon monoxide is a problem for many reasons

  • Binds to Hb and blocks oxygen from binding to it

Why Carbon Monoxide is a problem?

Interference with Oxygen Transport:
CO binds to hemoglobin in the blood, preventing it from carrying oxygen to
the body's tissues. This leads to oxygen deprivation, known as hypoxia.
• High Affinity for Hemoglobin:
CO has a much higher affinity for hemoglobin than oxygen, meaning it
binds more readily. This makes it difficult for oxygen to compete and be
transported effectively.
• Formation of Carboxyhemoglobin:
When CO binds to hemoglobin, it forms carboxyhemoglobin, which is a
stable and non-functional compound. This reduces the amount of
functional hemoglobin available to carry oxygen.