Lecture 10 - Energy production and oxygen consumption

Question 1

Partial pressure =

Answer 1

fractional concentration x pressure

fractional conc of O2 (0.2094) x 101.32 (atmospheric at seal level)

Question 2

What is the first step in the oxygen cascade

Answer 2

humidification in the airway through water vapour

reduces partial pressure of inspired air from 21 kPa to 19.9 lPa

Question 3

What is the 2nd step in the oxygen cascade

Answer 3

alveolar gas

Question 4

step 3 in oxygen cascade

Answer 4

alveolar-capillary diffusion - cross between alveolar and capillaries
not much difference

Question 5

What are the biggest PO2 drops in the cascade?

Answer 5

between humid air and alveolar gas and between arterial and venous blood

Question 6

step 4 of oxygen cascade

Answer 6

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

Question 7

Step 5 of oxygen cascade

Answer 7

tissue diffusion

Question 8

Step 6

Answer 8

diffusion within cell

Question 9

Describe the krogh model

Answer 9

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.

Question 10

Oxygen delivery calculation

amount of o2 leaving the heart in one minute

Answer 10

= O2 carried by haemoglobin + dissolved oxygen

approx 1000 ml/min

Question 11

What is oxygen consumption

Answer 11

amount of blood used by the body in one minute

approx 250 ml/min

Question 12

basal metabolic rate

Answer 12

VO2 at rest

Question 13

Normal values of VO2 at rest

Answer 13

Normal values - 200 ml/min
Relative to body size:
BMR = 45 Wm/-2
VO2 = 4.8 min/kg

Question 14

what is vo2

Answer 14

measure of oxygen consumption

Question 15

What are the factors affecting VO2

Answer 15

1. age - peak at age 0-2 years then falls for rest of life
2. temperature - metabolic rate doubles with every 10 degrees celcius
3. exercise

Question 16

What happens in anaemia

Answer 16

1. Increased DPG shifts O2-Hb curve to the right
2. reduced blood flow to non-essential organs - eg. skin, bowel
3. increased O2 extraction from blood
4. increase in cardiac output

Question 17

CO2=

Answer 17

(SO2 x [Hb] x 1.39) + 0.3

Question 18

DO2=

Answer 18

CO2 X CO (multiplied by amount of blood leaving heart)

Question 19

What is respiratory exchange ratio

Answer 19

the ratio of co2 production to o2 consumption

Question 20

normal RER =

Answer 20

1

Question 21

what is RER affected by?

Answer 21

acid base balance
hyperventialtion
metabolic fuel

Question 22

compare RER of carbs, fatty acids and proteins

Answer 22

more in carbs, least in Fatty acids

1, 0.7, 0.8

Question 23

What are the functions of oxygen

Answer 23

Glycolysis
Tricarboxylic acid cycle
Oxidative phosphorylation

Question 24

What is glycolysis

Answer 24

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

Question 25

what is the function of oxygen in the TCA cycle (Krebs)

Answer 25

Occurs most in the mitochondria
Acetyl CoA from glycolysis is converted to CO2
38 ATP molecules per glucose

Question 26

What happens in oxidative phosphorylation

Answer 26

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

Question 27

What are the main causes of fundamental hypoxia

Answer 27

Anoxic (lack of O2) - respiratory failire
stagnant (Lack of blood supply) - Angina
anaemic (lack of Hb) - Angina and low Hb

Question 28

Normal arterial PO2

Answer 28

13.5 kPa