13. Hemoglobin and Oxygen Transport

What are the three forms that CO2 is carried in the blood

1. Dissolved in plasma (more soluble than O2) 2. Carbaminohemoglobin - CO2 bound to amino acid in hemoglobin 3. Bicarbonate ions (major method of transport)

What are the different factors that affect Hb-oxygen affinity

1. PCO2 2. pH 3. 2,3 DPG 4. Exercise 5. Temperature

How many molecules of oxygen can each hemoglobin carry

4

What makes up hemoglobin

4 polypeptide globins (2 alpha and 2 beta)

What is the typical pH range

7.35-7.45

How prevalent is sickle cell anemia

8-11% of african americans

How much of the oxygen carried in the arterial blood is bound to hemoglobin

97%

At a PO2 of 100mmHg, what is Hb saturation At a PO2 of 40 mmHg, what is Hb saturation What does this represent

97% 75% This represents a 22% unloading of O2 between the arterials and veins

What is % oxyhemoglobin saturation

A quantitative assessment of how well the lungs have oxygenated the blood

What is the oxygen dissociation curve

A sigmoidal (s-shaped) curve that demonstrates the relationship between PO2, Hb saturation, and oxygen content in the blood

Respiratory acidosis or alkalosis occurs with what?

Abnormal CO2 plasma concentration

Metabolic acidosis or alkalosis occurs with what?

Abnormal bicarbonate plasma concentration

What happens to affinity at higher pCO2

Affinity decreases at a higher PCO2

What is the bohr effect

Affinity decreases at a lower pH and increases at a higher pH

What happens to oxygen affinity at high temperatures Why? Shift?

Affinity decreases at high temperatures and increases at low temperatures More O2 unloaded to mm during exercise Shift right

What is the major buffer in the blood

Bicarbonate

What buffers nonvolatile acids (lactic, fatty, ketone acids)

Bicarbonate, and can not be regulated by breathing but rather the kidneys

What buffers carbonic acid

Breathing

Why is affinity lower at a higher PCO2

CO2 binds Hb to displace O2

What is metabolic acidosis

Caused by excessive consumption of acids in diet (high protein/high fat), excessive production of non-volatile acids (lactic acid or ketone bodies) or loss of bicarbonate (diarrhea)

What is repiratory alkalosis

Caused by hyperventalation; "blow off" CO2, H+ decreases, pH increases

What is respiratory acidosis

Caused by hypoventilation; rise of CO2 which increases H+ and lowers pH

What is metabolic alkalosis

Caused by loss of acids (excessive vomiting) or over consumption of bicarbonates

What is sickle cell

Deoxygenated hemoglobin S polymerizes into long fibers, creating a sickle-shaped RBC This hinders flexibility and the ability to pass through small vessels

What is oxyhemoglobin called when reduced

Deoxyhemoglobin

Where is the remaining three percent of oxygen that is not bound to hemoglobin found

Dissolved in plasma

Does fetal hemoglobin or regular hemoglobin have a higher affinity for O2

Fetal so that oxygen can be transferred to the fetus

Where do RBCs get energy? What occurs during this process

From anaerobic metabolism of glucose (has no nucleus or mitochondira) During the process, 2,3 diphophoglyceric acid (2,3-DPG) is made

What is methemoglobin

Further oxidized iron (ferric state Fe3+) and can't bind to oxygen

What is carbaminohemoglobin

Hb bound to CO2

How do HbF, HbS, and HbA compare

HbF is functional vs. HbS, but HbF has a higher affinity for O2 than HbA

What is carboxyhemoglobin

Hemoglobin is bound with carbon monoxide Hemoglobin binds CO 200 times stronger than with O2

What is the affinity for oxygen of myoglobin

Higher affinity to oxygen; oxygen is only released when PO2 is very low

How does increased CO2 influence oxygen loading/unloading

Increased CO2 Increase in H+ Lowers pH Increases O2 unloading at tissues

What leads to decreased pH of blood and what does this do to oxygen unloading

Increased metabolism leads to increased H+ Lower pH Increases O2 unloading at the tissues

What does 2,3 DPG do to oxygen loading/unloading? Shift?

Increases oxygen unloading Shifts the oxyhemoglobin dissociation curve to the right

What is is oxyhemoglobin

Iron is in oxidized form (ferrous state Fe2+) and can bind with O2

What is the function of oxygen that remains in the veins

It serves as an oxygen reserve

At the steep part of the oxygen dissociation curve, small changes in PO2 produce what

Large changes in % saturation

Does a high PO2 favor loading or unloading

Loading

What regulates acid base balance

Lungs and kidneys

What is erythropoietin

Made in the kidneys stimulates hemoglobin/RBC production in red bone marrow when O2 lvels are low

Where is thalassemia found

Mainly in people of mediterranean heritage

How do you measure % oxyhemoglobin saturation

Measured with a pulse oximeter or blood-gas machine as SpO2 (peripheral capillary oxygen saturation)

What are the different forms of hemoglobin

Oxyhemoglobin Carbaminohemoglobin Methmeoglobin Carboxyhemoglobin

What does total O2 content of blood depend on

PO2 and hemoglobin concentration

What is the direction of oxygen loading/unloading dependent on

PO2 of the environment and affinity of hemoglobin for O2

What does SpO2 measure? What is normal in arterial blood

Percentage of oxyhemoglobin to total hemoglobin 97%

What causes thalassemia

Production of either alpha or beta chains is defective Increases synthesis of gamma chains Many mutations are possible giving a wide range of symptoms

What is muscle myoglobin

Red pigment found in skeletal and cardiac mm

How do kidneys help bicarbonate regulate pH

Releasing H+ in the urine and by producing more bicarbonate

What are the two types of acidosis

Respiratory Metabolic

What causes formation of methemoglobin

Some drugs

What is the function of muscle myoglobin

Stores oxygen and serves as go-between in transferring oxygen from blood to mitochondria

Decrease of pH shifts the oxygen dissociation curve which way?

To the right

What is the treatment for sickle cell, and how does it work

Treated with hydroxyurea Stimulates production of fetal hemoglobin (HbF)

What makes each form of hemoglobin different than one another

Unique colour and absorption spectrum

Is bicarbonate an acid or base

Weak base

What is acidosis

When blood pH falls below 7.35

What is alkalosis

When blood pH rises above 7.45

What is oxygen loading

When hemoglobin binds to oxygen in the lungs (external respiration)

What is oxygen unloading

When oxyhemoglobin drops off oxygen to the tissues (internal respiration)

Is muscle myoglobin similar to hemoglobin

Yes, but with 1 heme so it can only carry 1 oxygem molecule

What is normal blood pH maintained when

bicarbonate and CO2 are at a ratio of 20:1

What kind of hemoglobin cannot bind to 2,3 DPG

fetal hemoglobin (hemoglobin F)

Sickle cell blood flow to organs?

restricted and RBCs hemolyse