Lecture 10 - Energy production and oxygen consumption Flashcards
Partial pressure =
fractional concentration x pressure
fractional conc of O2 (0.2094) x 101.32 (atmospheric at seal level)
What is the first step in the oxygen cascade
humidification in the airway through water vapour
reduces partial pressure of inspired air from 21 kPa to 19.9 lPa
What is the 2nd step in the oxygen cascade
alveolar gas
step 3 in oxygen cascade
alveolar-capillary diffusion - cross between alveolar and capillaries
not much difference
What are the biggest PO2 drops in the cascade?
between humid air and alveolar gas and between arterial and venous blood
step 4 of oxygen cascade
ventilation-perfusion mismatch and shunt
deoxygenated blood fusing with oxygenated blood to form arterial blood
shunting - when blood isnt oxygenated - bypasses
we all have around 2.5% of shunting
Step 5 of oxygen cascade
tissue diffusion
Step 6
diffusion within cell
Describe the krogh model
This unit structure implies that each section of capillary is responsible for the supply to a corresponding cylindrical section of surrounding tissue.
lethal corner - venule end of capillary - cells at this end will be the first to become hypoxic
o2 tissue diffusion
all arteriole to venule - pressure drops
all cells have exposure to different O2 levels.
Oxygen delivery calculation
amount of o2 leaving the heart in one minute
= O2 carried by haemoglobin + dissolved oxygen
approx 1000 ml/min
What is oxygen consumption
amount of blood used by the body in one minute
approx 250 ml/min
basal metabolic rate
VO2 at rest
Normal values of VO2 at rest
Normal values - 200 ml/min
Relative to body size:
BMR = 45 Wm/-2
VO2 = 4.8 min/kg
what is vo2
measure of oxygen consumption
What are the factors affecting VO2
- age - peak at age 0-2 years then falls for rest of life
- temperature - metabolic rate doubles with every 10 degrees celcius
- exercise
What happens in anaemia
- Increased DPG shifts O2-Hb curve to the right
- reduced blood flow to non-essential organs - eg. skin, bowel
- increased O2 extraction from blood
- increase in cardiac output
CO2=
(SO2 x [Hb] x 1.39) + 0.3
DO2=
CO2 X CO (multiplied by amount of blood leaving heart)
What is respiratory exchange ratio
the ratio of co2 production to o2 consumption
normal RER =
1
what is RER affected by?
acid base balance
hyperventialtion
metabolic fuel
compare RER of carbs, fatty acids and proteins
more in carbs, least in Fatty acids
1, 0.7, 0.8
What are the functions of oxygen
Glycolysis
Tricarboxylic acid cycle
Oxidative phosphorylation
What is glycolysis
occurs in the cytoplasm
glucose to pyruvate or lacate in the presence of or absence of oxygen
however no oxygen is required in the process
2ATP molecules are produced per gluocse
what is the function of oxygen in the TCA cycle (Krebs)
Occurs most in the mitochondria
Acetyl CoA from glycolysis is converted to CO2
38 ATP molecules per glucose
What happens in oxidative phosphorylation
occurs in the mitochondria
NADH provides H+
H+ combines with O2 to produce water
ATP produced
What are the main causes of fundamental hypoxia
Anoxic (lack of O2) - respiratory failire
stagnant (Lack of blood supply) - Angina
anaemic (lack of Hb) - Angina and low Hb
Normal arterial PO2
13.5 kPa
