Respiratory strand: Lecture 10 - Energy Production & Oxygen Consumption

Question 1

What are the six steps in the oxygen cascade?

Answer 1

1. Humidification
2. Alveolar gas
3. Alveolar-capillary diffusion
4. Ventilation-perfusion mismatch and shunt
5. Tissue diffusion
6. Diffusion within cell e.g mitochondria

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Question 2

What is the Krogh model?

Answer 2

Krogh model is a scientific theory explaining the concentration of molecular oxygen through a cylindrical capillary tube relative to the position over the capillary tube’s length.

Question 3

What is the definition of oxygen delivery?

Answer 3

Amount of oxygen leaving the heart in one minute (DO2)

Question 4

How do you work out oxygen delivery?

Answer 4

1. Work out the amount of oxygen in the blood (oxygen content)
   = oxygen carried by haemoglobin + dissolved oxygen
2. Multiplied by amount of blood leaving the heart (cardiac output)

so oxygen delivery = oxygen content x cardiac output

Question 5

What is the definition of oxygen consumption? (VO2)

Answer 5

Amount of oxygen used by the body in one minute (VO2)

Question 6

What is basal metabolic rate?

Answer 6

Minimum VO2 at rest (min oxygen consumption)

Question 7

How do we measure oxygen consumption?

Answer 7

• direct calorimetry
• indirect calorimetry:
• arterio-venous CO2 difference
• inspired-expired O2 volume difference

Question 8

What factors affect VO2?

Answer 8

1. Age - peak at 0-2yrs, then falls for rest of life
2. Temperature - metabolic rate doubles with every 10%
3. Exercise
4. Gender

Question 9

What are the physiological responses of acquiring anaemia?

Answer 9

1. Increased 2,3,-DPG shifts O2-Hb curve to right - decreased affinity
2. Reduced blood flow to non-essential organs e.g skin, bowels
3. Increased oxygen extraction from the blood
4. Increase in cardiac output

Question 10

What is the definition of respiratory exchange ratio?

Answer 10

The ratio of carbon dioxide production (VO2) to oxygen consumption (VO2)

Question 11

What is the respiratory quotient?

Answer 11

RER at rest

Question 12

What is the normal value of the respiratory quotient?

Answer 12

1

Question 13

What is the RER affected by?

Answer 13

• Acid base balance
• hyperventilation
• metabolic fuel

Question 14

Why might we carry out a cardio-pulmonary exercise test?

Answer 14

To try to work out if a patient is fit before operating

Question 15

What is the function of oxygen?

Answer 15

To generate energy via a 3 stage process:

1. Glycolysis
2. Tricarboxylic acid cycle (Krebs cycle)
3. Oxidative phosphorylation

Question 16

Where does glycolysis occur and what does it produce?

Answer 16

• occurs in cytoplasm
• glucose to pyruvate or lactate
• no oxygen required
• 2x ATP molecules per glucose

Question 17

Where does the TCA cycle occur and what does it produce? (Krebs)

Answer 17

• occur mostly in mitochondria
• acetyl coA (from glycolysis) to CO2
• 38 ATP molecules per glucose

Question 18

Where does oxidative phosphorylation occur and what does it produce?

Answer 18

• occurs in mitochondria
• NADH provides H+
• H+ combines with O2 to produce water
• ATP produced

Question 19

What are the 3 causes of cellular hypoxia?

Answer 19

• anoxia (lack of O2 in blood)
• Anaemia (lack of haemoglobin)
• Stagnant (lack of blood supply)

Question 20

What will anoxia cause?

Answer 20

Respiratory failure

Question 21

What is angina?

Answer 21

chest pain caused by reduced blood flow to the heart muscles