😀 EASY

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
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 3
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 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
Question 4
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 4 Explanation: 
Haemoglobin dramatically increases blood oxygen content by increasing its solubility in blood through protein binding
Question 5
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 6
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 7
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 8
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 9
What is the shape of the oxygen-haemoglobin saturation curve and what is the expla
A
Exponential
B
Parabolic
C
Sigmoidal
D
Linear
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.
Question 10
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 11
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 11 Explanation: 
In anaemia, you can have a normal oxygen saturation reading even though haemoglobin content has dramatically decreased
Question 12
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 13
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 14
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 15
How do the above molecules cause haemoglobin to favour its T state?
A
It destroys the haemoglobin causing it 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 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.
Question 16
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 17
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 18
Which of the following has the highest blood solubility?
A
CO
B
CO2
C
O2
D
H202
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