Unit 2. Lesson 3 : Hemoglobin, O2 transport and Bohr shift

What is Hemoglobin

Hemoglobin (Hb) is a protein responsible for the O2 transport

• consists of 4 subunits containing iron atoms bound to a heme

• When de-oxygenated, Hb can still carry trace amounts of CO2 as well

What is a Heme 

A heme is a ring shaped molecule that holds Iron

• Heme: ring-shaped molecule that holds one iron atom.

• Iron: atom in heme that binds oxygen.

What is cooperative binding

Cooperative binding is when the affinity (want) for more O2 increases with each bound O2

This is seen in Hb, as its binding potential changes with each O2 molecule its bind to

What are the characteristics of an Adult Hb dissociation curve

A dissociation curve is a graph that displays the relationship between the percent of oxygen saturation (the amount of bound oxygen) and oxygen partial pressure (quantity of oxygen)

• a sigmoidal ( S-shaped) curve because of cooperative binding

• Hb can only bind to 4 O2 molecules so it peaks out

What are the characteristics of an Fetal Hb dissociation curve

Has a higher O2 affinity than its Adult counterpart which results in a steeper graph as it binds to oxygen quicker

• fetal Hb can be induced in adults to treat diseases such as sickle cell anaemia 

When does Hb release and bind to O2

• when there is low O2 around Hb, Hb will release O2 to reach equilibrium (High to low)

• when there is high O2 around Hb, Hb will bind O2 to reach equilibrium (low to high)

• for example, if there is low O2 in your feet, your Hb will release O2, giving some to the feet

CO2 and blood pH: CO2 released in blood results in what

CO2 released into the blood results in carbonic acid in blood plasma

this raises lowers the pH of the blood hence raising its acidity 

CO2 and blood pH: CO2 in the blood is monitored how

CO2 in the blood is monitored by chemosensors in organs that allows them to respond to the acidity accordingly 

for example: 

• Kidneys buffer pH change and absorb/excrete HCO3

• The brain alters respiration rate to expire CO2 more rapidly

In summary, the acidity is monitored by chemosensors in organs that allows them to identify the problem and respond accordingly

Bohr shift: How does blood pH affect Hb

Changes in blood pH affects Hb’s affinity for O2

What is the Bohr effect

A decrease in pH results in Hb releasing more O2