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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Question 1
What is the purpose of maximising oxygen transport in the blood?
A
Cells attach waste products to oxygen, which prevents toxic build-up in cells
B
Cells use oxygen to produce ATP through oxidative respiration, which must match demand
C
Because blood oxygen concentration always needs to be higher than carbon dioxide concentration
D
Because red blood cells need oxygen for their structural integrity
Question 2
How much ATP is produced with aerobic respiration in comparison to anaerobic respiration?
A
36 ATP vs 2 ATP
B
38 ATP vs 4 ATP
C
2 ATP vs 38 ATP
D
It is the same in both cases
Question 3
Describe the oxygen cascade
A
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
B
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.
C
Beginning in the lungs at 21 KPA, becoming 21 KPA in perfused alveoli to around 13 KPA in the tissues.
D
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
Question 4
A Patient has a pulmonary embolism (a substance that blocks lung perfusion), meaning that new blood cannot be perfused by a certain alveolus. What is the pO2 in this alveolus?
A
13 KPa
B
14 KPa
C
15 KPa
D
21 KPa
Question 4 Explanation: 
The pO2 at atmospheric pressure is 21 KPa. Since there is no longer any oxygen diffusing into the blood at this alveolus, the pO2 does not go down the oxygen cascade (which decreases its concentration in the alveolus) and equilibrates to 21 KPa
Question 5
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?
A
The surface area of the alveoli increases when you take in a deep breath
B
By decreasing body temperature as you inhale
C
Through the production and use of haemoglobin
D
By reducing water vapour in the alveoli
Question 5 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
Question 6
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
A
A
B
T
C
D (more specifically, molecular weight)
D
D (more specifically, solubility)
Question 6 Explanation: 
Haemoglobin dramatically increases blood oxygen content by increasing its solubility in blood through protein binding
Question 7
Why is it useful to have a readily reversible reaction between oxygen and iron on the haemoglobin molecule?
A
The oxygen stabilises the haemoglobin molecule as it travels through the blood
B
You need a molecule that will easily bind to haemoglobin when there is oxygen available and release it where it is needed
C
So you can place other ions on the haemoglobin molecule
D
Depending on the needs of the cell, either iron or oxygen can be released
Question 8
What subunits make up the quaternary structure of haemoglobin?
A
2 alpha and 2 beta subunits, each containing a haem group
B
4 alpha subunits, each containing a haem group
C
4 beta subunits, each containing a haem group
D
2 gamma and 2 theta subunits , each containing a haem group
Question 9
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?
A
Total blood oxygen content is found in 2 forms = attached to haemoglobin and dissolved in the plasma
B
Total blood oxygen content is found in 2 forms = in water and dissolved in the plasma
C
Total blood oxygen content is found in 3 forms = in water, dissolved in the plasma and carried by red blood cells
D
Total blood oxygen content is found in 2 forms = in carbon dioxide and dissolved in the plasma
Question 10
What are the 2 states of the haemoglobin molecule, and which is favoured in the lungs vs the tissues?
A
Tense (T) and relaxed (R) state. The tense state is favoured in the tissues and the relaxed state is favoured in the lungs
B
Tetrameric (T) and released (R) state. The tense state is favoured in the tissues and the relaxed state is favoured in the lungs
C
Tetrameric (T) and released (R) state. The tense state is favoured in the lungs and the relaxed state is favoured in the lungs
D
Tense (T) and relaxed (R) state. The tense state is favoured in the lungs and the relaxed state is favoured in the tissues
Question 11
The oxygen saturation curve of all saturated haemoglobin molecules at a certain partial pressure of oxygen mimic to the behaviour of an individual haemoglobin molecule. Describe how this is the case.
A
The oxygen saturation curve of all haemoglobin is exponential. When one haemoglobin molecule becomes saturated with oxygen, the other molecules follow
B
The oxygen saturation curve of all haemoglobin is parabolic. Oxygen saturation rises, plateaus and then descends as it gets to the tissues
C
The oxygen saturation curve of all haemoglobin is sigmoidal. This is mimicked at an individual level by positive co operativity of oxygen binding to the 4 haem subunits of haemoglobin
D
The oxygen saturation curve of all haemoglobin is linear. If oxygen is not used by the tissues, saturated haemoglobin molecules add up
Question 11 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 until saturation occurs
Question 12
At approximately what partial pressure does the oxygen haemoglobin dissociation curve saturate? what is the partial pressure in the tissues?
A
21 KPa; 13 KPa
B
13.3 KPa; 6 KPa
C
6 KPa; 3 KPa
D
6 KPa; 6 KPa
Question 13
You take the oxygen saturation of a patient with anaemia and find that it is 97% saturated. How is this possible?
A
They do not actually have anaemia
B
In emergency situations the iron in the heam group can be replaced with magnesium
C
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
D
The oxygen content in the blood increases in anaemia to compensate for the loss of haemoglobin
Question 13 Explanation: 
In anaemia, you can have a normal oxygen saturation reading even though haemoglobin content has dramatically decreased
Question 14
How much oxygen is normally offloaded from haemoglobin into the tissues before getting back to the lungs?
A
60%
B
50%
C
40%
D
30%
Question 15
Why does venous blood still contain oxygenated haemoglobin?
A
Oxygen is required to maintain the structural integrity of haemoglobin
B
So there is a reserve of oxygen in case of increased metabolic demand
C
This is an inefficient system
D
This oxygen cannot be unbound
Question 16
Which of the following molecules do not encourage the offloading of oxygen from haemoglobin in the Bohr effect?
A
H+
B
2,3 BPG
C
CO2
D
O2
Question 17
How do the above molecules cause haemoglobin to favour it’s T-State?
A
It destroys the haemoglobin causing to release oxygen
B
They are allosteric modulators of haemoglobin
C
They bind to oxygen more strongly than haemoglobin
D
They replace oxygen on haemoglobin’s haem group
Question 18
Which of the following is not a way in which the body responds to chronic hypoxia?
A
By increasing ventilation
B
By decreasing ventilation
C
Though the release of EPO
D
By increasing capillary density
Question 19
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?
A
The patient is not excreting CO2
B
The kidney is not able to produce EPO in response to low oxygen levels
C
The patient is not excreting enough protons
D
The patient is not excreting enough bicarbonate
Question 20
Which of the following has the highest blood solubility?
A
CO
B
CO2
C
O2
D
H202
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