This MCQ relates to the learning outcomes covered in the oxygen transport lecture. Good luck!
Reviewed by Daniel Mercer on 11th October 2019
Oxygen Transport MCQ
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What is the purpose of maximising oxygen transport in the blood?
Cells attach waste products to oxygen, which prevents toxic build-up in cells
Cells use oxygen to produce ATP through oxidative respiration, which must match demand
Because blood oxygen concentration always needs to be higher than carbon dioxide concentration
Because red blood cells need oxygen for their structural integrity
Describe the oxygen cascade
O2 travels down the oxygen cascade beginning the perfused alveoli to around 6 KPA in the tissues and returns as venous blood at 3 KPA
O2 travels down the oxygen cascade beginning in the atmosphere at 13 KPA, becoming 6 KPA on entering the lungs and perfused alveoli to around 2 KPA in the tissues.
Beginning in the lungs at 21 KPA, becoming 21 KPA in perfused alveoli to around 13 KPA in the tissues.
O2 travels down the oxygen cascade beginning in the atmosphere at 21 KPA, becoming 13 KPA on entering the lungs and perfused alveoli, to around 6 KPA in the tissues
Oxygen normally has a low solubility in blood plasma (3ml/L), whereas resting oxygen consumption in the body is 250 ml/min. How does the body overcome oxygen’s relatively low solubility to meet demand?
The surface area of the alveoli increases when you take in a deep breath
By decreasing body temperature as you inhale
Through the production and use of haemoglobin
By reducing water vapour in the alveoli
Question 3 Explanation:
Haemoglobin dramatically increases blood oxygen content to meet the demands of the body. So much so that blood alveolar concentration equilibrates with alveolar oxygen by the time it passes through 25% of the capillary
Which aspect of this equation can be altered to increase the diffusion rate of oxygen in the blood? Diffusion rate = α A/T x D x (P1 -P2) A= Area, T = Thickness, D= Diffusion constant (Sol / √MW [Solubility, Molecular weight]),P = partial pressure
D (more specifically, molecular weight)
D (more specifically, solubility)
Question 4 Explanation:
Haemoglobin dramatically increases blood oxygen content by increasing its solubility in blood through protein binding
Why is it useful to have a readily reversible reaction between oxygen and iron on the haemoglobin molecule?
The oxygen stabilises the haemoglobin molecule as it travels through the blood
You need a molecule that will easily bind to haemoglobin when there is oxygen available and release it where it is needed
So you can place other ions on the haemoglobin molecule
Depending on the needs of the cell, either iron or oxygen can be released
What subunits make up the quaternary structure of haemoglobin?
2 alpha and 2 beta subunits, each containing a haem group
4 alpha subunits, each containing a haem group
4 beta subunits, each containing a haem group
2 gamma and 2 theta subunits , each containing a haem group
You pull out a sample of blood from a volunteer to determine what composes the total oxygen content in the blood. What do you find?
Total blood oxygen content is found in 2 forms = attached to haemoglobin and dissolved in the plasma
Total blood oxygen content is found in 2 forms = in water and dissolved in the plasma
Total blood oxygen content is found in 3 forms = in water, dissolved in the plasma and carried by red blood cells
Total blood oxygen content is found in 2 forms = in carbon dioxide and dissolved in the plasma
What are the 2 states of the haemoglobin molecule, and which is favoured in the lungs vs the tissues?
Tense (T) and relaxed (R) state. The tense state is favoured in the tissues and the relaxed state is favoured in the lungs
Tetrameric (T) and released (R) state. The tense state is favoured in the tissues and the relaxed state is favoured in the lungs
Tetrameric (T) and released (R) state. The tense state is favoured in the lungs and the relaxed state is favoured in the lungs
Tense (T) and relaxed (R) state. The tense state is favoured in the lungs and the relaxed state is favoured in the tissues
What is the shape of the oxygen-haemoglobin saturation curve and what is the expla
Question 9 Explanation:
Binding of the first oxygen molecule is the most difficult due to the steric hindrance (hidden binding site) of haem molecules on haemoglobin. It thus requires a higher partial pressure of oxygen to increase the probability of oxygen collisions with the haem subunit. When the first binding occurs, a conformational change occurs in the protein to better expose the remaining binding sites on haemoglobin. Subsequent binding of oxygen to haemoglobin facilitates binding of the following subunits to oxygen more easily. As haemoglobin approaches saturation, it is harder for oxygen to find a free binding site, creating the plateau of the sigmoidal curve.
At approximately what partial pressure does the oxygen haemoglobin dissociation curve saturate? what is the partial pressure in the tissues?
21 KPa; 13 KPa
13.3 KPa; 6 KPa
6 KPa; 3 KPa
6 KPa; 6 KPa
You take the oxygen saturation of a patient with anaemia and find that it is 97% saturated. How is this possible?
They do not actually have anaemia
In emergency situations the iron in the heam group can be replaced with magnesium
Pulse oximetry only tells you about haemoglobin’s ability to saturate with oxygen and nothing about the quantity of red blood cells in the blood
The oxygen content in the blood increases in anaemia to compensate for the loss of haemoglobin
Question 11 Explanation:
In anaemia, you can have a normal oxygen saturation reading even though haemoglobin content has dramatically decreased
How much oxygen is normally offloaded from haemoglobin into the tissues before getting back to the lungs?
Why does venous blood still contain oxygenated haemoglobin?
Oxygen is required to maintain the structural integrity of haemoglobin
So there is a reserve of oxygen in case of increased metabolic demand
This is an inefficient system
This oxygen cannot be unbound
Which of the following molecules do not encourage the offloading of oxygen from haemoglobin in the Bohr effect?
How do the above molecules cause haemoglobin to favour its T state?
It destroys the haemoglobin causing it to release oxygen
They are allosteric modulators of haemoglobin
They bind to oxygen more strongly than haemoglobin
They replace oxygen on haemoglobin’s haem group
Question 15 Explanation:
2,3-BPG and protons (H+) favour the R state of haemoglobin, making it less likely to bind oxygen. Carbon dioxide gets converted into acid in the blood, increasing the concentration of protons.
Which of the following is not a way in which the body responds to chronic hypoxia?
By increasing ventilation
By decreasing ventilation
Though the release of EPO
By increasing capillary density
Your patient has kidney failure for a while and you have noticed recently that their respiration rate has increased above the normal range. What could be an explanation for this?
The patient is not excreting CO2
The kidney is not able to produce EPO in response to low oxygen levels
The patient is not excreting enough protons
The patient is not excreting enough bicarbonate
Which of the following has the highest blood solubility?
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