Energy Production and Oxygen Consumption

What does the oxygen cascade show?

how PO2 decreases as air moves through the respiratory system and into cells

What is the first stage of the oxygen cascade where PO2 is lowered?

humidification

What stage lowers PO2 significantly after humidification in the oxygen cascade?

air moving into alveoli and mixing with CO2

True or false: when O2 moving from alveoli to capillary, the PO2 remains about the same

true

Why does PO2 decline when oxygen moves into arterial vessels from capillaries?

the ventilation-perfusion mismatch and shunts mean that some areas of blood are not ventilated and some areas of the lung are not perfused, resulting in partially oxygenated blood

What is the mean tissue PO2?

5kPa

What is the name given to the PO2 in mitochondria used in cellular respiration?

Pasteur's point

What is the PO2 in the mitochondria following tissue diffusion?

>0.15kPa

What does ischaemic mean?

deficient blood supply

Give the definition of oxygen delivery:

the amount of oxygen leaving the heart in one minute

What abbreviation is given to oxygen delivery:

DO2 (dot over the D)

How is oxygen delivery calculated?

amount of oxygen in the blood x amount of blood leaving the heart

What is the approx. amount of O2 in the blood for a healthy person at rest?

19 ml/dl-1

How is the amount of oxygen in the blood calculated?

oxygen carried by haemoglobin + dissolved oxygen

What is the normal resting cardiac output?

5.25 L/min

What is the normal oxygen delivery in a healthy, resting individual?

1000 ml/min

Give the definition of oxygen consumption:

the amount of oxygen used by the body in one minute

What is the abbreviation given to oxygen consumption:

VO2 (dot over the V)

What does a dot over a letter abbreviation indicate?

by time

What is basal metabolic rate?

the body's resting rate of energy expenditure

What is the approx. oxygen consumption for a healthy, resting individual?

200 ml/min

True or false: body mass does not affect oxygen consumption

false

Which method is used most commonly to measure oxygen consumption, direct or indirect calorimetry?

indirect calorimetry

What is the average oxygen consumption per kg body mass in healthy, resting individuals?

4.8 ml min-1 kg-1

What are the two indirect calorimetry methods used to measure oxygen consumption?

1) anterior-venous O2 difference

2) inspired-expired O2 volume difference

How can arterio-venous O2 difference be used to measure oxygen consumption?

it measures how much O2 leaves the heart verses how much is returned

Give 3 factors that affect oxygen consumption:

1) age

2) temperature

3) exercise

During what years of life is oxygen consumption highest?

0-2 years

Fill the gap: metabolic rate increases with every __ degrees C

10 degree C

What does MET stand for?

metabolic equivalent task

What does a MET of 8 mean?

the activity will use x8 of your basal O2 consumption

Give 4 physiological compensation methods used by anaemics to counter lower O2 content:

1) increased 2,3 DPG levels to promote O2 release

2) reduced flow to non essential organs like skin

3) increased oxygen extraction from blood

4) increased cardiac output to maintain oxygen delivery

How does PO2 change with altitude?

it decreases

How do climbers physiologically adapt when climbing at high alitutudes?

their haemoglobin concentration increases

Define the respiratory exchange ratio:

the ratio of CO2 production to oxygen consumption

What is the normal value of the RER?

1.0

What is the respiratory quotient in relation to RER?

the RER at rest

Give 3 factors that affect the respiratory exchange ratio:

1) changes in acid base balance

2) hyperventilation

3) metabolic fuel

What is the RER for carbohydrates and why?

1.0 as for every C, there is an O

What is the RER for fatty acids and why?

0.7, far fewer Os found in fatty food

What is the RER for proteins?

0.8

What is the name of the testing used to assess RER pre-surgery?

cardio-pulmonary exercise testing

Describe cardio-pulmonary exercise test graphs:

VO2 is found on the x axis and VCO2 is found on the y, meaning RER is plotted

Where is the anaerobic threshold identified on cardio-pulmonary exercise test graphs?

at the hockey-stick bend

What is the main use of the cardio-pulmonary exercise test?

to assess if a patient can cope with oxygen stress during surgery

True or false: glycolysis requires oxygen

false

Where does glycolysis take place?

cytoplasm

How many ATP molecules are produced in glycolysis per glucose molecule?

2

What final molecule is produced in glycolysis from glucose?

pyruvate

How many ATP molecules are produced in the Kreb's cycle per glucose molecule?

38

How is oxygen used in the electron transport chain?

it combines with H+ ions from NADH to form H2O

What are the 3 causes of cellular hypoxia according to Barcroft?

1) anoxic

2) stagnant

3) anaemic

What is meant by stagnant in relation to hypoxia?

lack of blood supply

What is meant by anoxia?

lack of oxygen in the blood