L6 Carriage of O2 and CO2 in the blood Flashcards
What are the two methods of oxygen transportation the body? How much is transported in these methods?
- Dissolved in blood
Some oxygen is dissolved in the blood. The lower the temperature the more gas dissolved.
At body temperature 0.29 ml/dl is dissolved in the blood. - Bound to haemoglobin
19 ml/dl of oxygen is bound to haemoglobin in the blood.
1.39 ml of oxygen is carried per gram of haemoglobin.
What are the methods of carbon dioxide transportation in the body?
- Dissolved in blood. CO2 is more soluble in blood and water than oxygen. At 37°C = 3ml CO2 per dl of blood.
- Carbon dioxide can bind to the terminal amino group to form carbinoaminohaemogobin. There is only 4 terminal groups. It can also bind to side chains of lysine and arginine on haemoglobin. 4ml CO2 per dl in blood.
- As bicarbonate ions. This account for 45ml CO2 per dl of blood.
What is Cooperativity?
Cooperativity - binding of one oxygen to a haemoglobin changes the shape of the other globins to make it easier for other oxygen molecules to bind. This makes it progressively easier for oxygen to bind until all for oxygen molecules are attached. The Hb molecules moves from the tense to relaxed state.
We only use 25% of the oxygen available in the blood. The last oxygen is hopping on and off of the haemoglobin and the others remain bound. This is easiest, the affinity is at the highest due to the cooperativity.
What is normal arterial blood oxygen pressure?
12.5 kPa
What is normal venous blood oxygen pressure?
6.3kPa
What factors can affect the haemoglobin-oxygen dissociation curve?
- BPG concentration - 2,3-BPG is part of glycolysis. It is a product and controls the shape of the curve. BPG shifts the curve to make dissociation more favourable for us. BPG levels may change at altitude to make oxygen carriage better. Also occurs with anaemia. At a higher BPG concentration, the curve is shifted to the right as more oxygen is released to the tissues.
- pH
- Carbon Dioixide concentration. A higher concentration, and therefore lower pH shifts the curve to the right.
- Temperature. A low temperature shifts the curve to the left.
What is a buffer?
A buffer solution is an aqueous solution consisting of a mixture of a weak acid and its conjugate base, or vice versa. Its pH changes very little when a small amount of strong acid or base is added to it. Buffer solutions are used as a means of keeping pH at a nearly constant value in a wide variety of chemical applications.
What are the main buffers in the blood?
- Proteins can act as buffers especially those with many Histidine residues. Histidine is negatively charged and so can interact with the protons to alter pH. The terminal carboxyl and amino groups on the primary structure can also interact and enable the pH to remain constant. Haemoglobin is a very good example of this. Plasma proteins also play a part in the buffering system.
- Phosphates are important buffers intracellularly but do not play a major part in extracellular pH maintenance.
- Bicarbonate ions.
What is the role of carbonic anhydrase? How is it able to do this?
Carbonic anhydrase is an enzyme that converts carbon dioxide and water into carbonic acid. This acid dissociates into protons and bicarbonate ions. It is able to do so using a Zinc cofactor.
What is the Hamburger effect?
Chlorideshift(also known as theHamburgerphenomenon) is a process which occurs in a cardiovascular system and refers to the exchange of bicarbonate (HCO3−) and chloride (Cl−) across the membrane of red blood cells (RBCs).
What is the Henderson-Hasselbalch effect?
The Henderson–Hasselbalch equation relates the pH of a solution containing a mixture of the two components to the acid dissociation constant, Ka, and the concentrations of the species in solution.
pH = pK + log10[HCO3-]/[CO2]
7.4 = 6.1 + log10[24mmol/L]/[1.2 mol/L]
What is the Haldane effect?
The Haldane effect is a property of haemoglobin first described by John Scott Haldane. Oxygenation of blood in the lungs displaces carbon dioxide from hemoglobin which increases the removal of carbon dioxide.
What is metabolic acidosis?
A low pH caused by low bicarbonate levels as the kidneys are removing too much ions. Metabolic acidosis occurs when the body produces too much acid. It can also occur when the kidneys are not removing enough acid from the body.
What is metabolic alkalosis?
Metabolic alkalosis is a metabolic condition in which the pH of tissue is elevated beyond the normal range (7.35–7.45). This is the result of decreased hydrogen ion concentration, leading to increased bicarbonate, or alternatively a direct result of increased bicarbonate concentrations.
What is respiratory acidosis?
Respiratory acidosis is a condition that occurs when the lungs can’t remove enough of the carbon dioxide (CO2) produced by the body. Excess CO2 causes the pH of blood and other bodily fluids to decrease, making them too acidic.
