The Oxygen Cascade II

Question 1

Steps in Oxygen Cascade

Answer 1

Convection (Advection)
VO2 = (VI x FIO2) - (VE x FEO2)

Diffusion
VO2 = DLO2(PAO2 - PcO2)

Convection
VO2 = Q (CaO2 - CvO2)

Diffusion
VO2 = DtO2(PcO2 - PtO2)

Question 2

As a consequence of our absolute dependence

on aerobic metabolism, we have evolved:

Answer 2

• A large surface area for gas exchange (alveoli)
• An efficient transport system
(heart & circulation)
• An oxygen transport protein (haemoglobin)

Question 3

Pulmonary capillary PO2 as a function of RBC transit time graph shows

Answer 3

Pulmonary capillary PO2 as a function of
RBC transit time
Line reaches 98% in one quarter of time of transit (by 0.25)

Question 4

O2 is carried in the blood in two forms:

Answer 4

• As a gas in simple solution in the plasma,
i.e. physically dissolved
– (only 3 mL L-1 (100 mm Hg PO2)-1, since plasma sO2
is low)
• As oxy-haemoglobin in erythyrocytes (RBCs)
– (1.34 mL O2 g-1 Hb, ~ 200 mL if [Hb] is 150 g L-1)

Question 5

Gases dissolved in solution obey Henry’s Law:

i.e.

Answer 5

the amount dissolved is proportional to the
partial pressure of the gas, and its solubility
c= solubity constant*P

Question 6

Humans have the red-colored hemoglobin as their
_________ to increase the O2-carrying capacity of
the blood.

Answer 6

respiratory pigment

Question 7

Hemoglobin is confined to the
• Increases the O2-carrying capacity of the blood
between

Answer 7

RBCs

65 - 70 x.

Question 8

• Each RBC has about ____x 106 Hb molecules, and

each mL of blood contains ~5 X 109 RBCs.

Answer 8

300

Question 9

Hb molecule made up of 4 subunits. Describe

Answer 9

(globin, 2 α & 2 β), each with 1

haem (a porphyrin compound) at the centre.

Question 10

• Each haem contains ________ that combines with O2.

Answer 10

an iron atom (ferrous form, Fe2+)

Question 11

• Hb carries up to ~_____mL O2 LBlood-1

Answer 11

200

Question 12

Relaxed binding structure of haemoglobin

Answer 12

oxyhaemoglobin

Question 13

Tight binding structure of haemoglobin

Answer 13

deoxyhaemoglobin

Question 14

As the 4 haem groups unload O2, _______ binds (1:1)

strongly to the b subunits (globins).

Answer 14

2,3-DPG (2,3-BPG)

Question 15

• Globin (i.e. the 4 subunits) can bind to

Answer 15

H+ and CO2.

Question 16

• 2,3-DPG (2,3-BPG) 2,3-Diphosphoglycerate is a ______metabolite that
alters the?

Answer 16

glycolytic

the affinity of Hb for O2.

Question 17

• 2,3-DPG is increased in blood by

Answer 17

hypoxia, low [Hb], and increased pH.

Question 18

Under basal conditions the tissues require about 5 mLs
O2 per 100 mLs blood.
•To achieve this, PO2 must

Answer 18

less than 40 mm Hg.

Question 19

During exercise the tissues require up to ~20 x more O2.

This achieved without a huge decr. PO2 because:

Answer 19

• Steep slope of HbO2 curve

* Increased tissue blood flow caused by the small drop ¯PO2. (Hypoxic vasodilation of tissue capillaries)

Question 20

The range of PO2 values in the tissues is held tightly

between

Answer 20

40 - 15 mm Hg.

Question 21

Haldane effect.LUNGS

Answer 21

Binding of Hb with O2 tends to displace

CO2 from the blood:

Question 22

Bohr effect. TISSUES

Answer 22

Increase in blood [CO2] causes O2 to be

displaced from Hb:

Question 23

Anaerobic threshold is a physiological indice of .
• Above this point ______accumulates in blood.
• Has a high correlation with an athlete’s

Answer 23

performance
lactate
endurance performance.

Question 24

There are two ATP-generating systems,

Answer 24

glycolysis and

oxidative phosphorylation.

Question 25

_______does not require O2 and has La− as its endproduct, because the equilibrium of the LDH reaction is
markedly in favor of La− .
• La− , then, is an immediate reservoir supplying pyruvate
to mitochondria for _____________
• Therefore, La− stands at the intersection of _____and _______metabolism of carbohydrate
fuel.

Answer 25

Glycolysis
complete oxidative combustion.
anaerobic and aerobic

Question 26

2 ways Elimination of CO2

Answer 26

CO2 is excreted from the blood:
• as CO2 in the lungs
• as HCO3
- in the kidney
CO2 is excreted from the body:
• by exhalation
• by micturition

Question 27

_____ + ________ _H2CO3 H+ + HCO3-

Answer 27

CO2 + H2O

Question 28

CO2 + H2O_H2CO3 catalysed by?

Answer 28

in RBCs by carbonic anhydrase

CA) to form carbonic acid (H2CO3

Question 29

CO2 is transported in the blood by:

Answer 29

• ~ 7% as CO2 in simple solution (high sCO2)
• ~ 23% as HbCO2 (carbaminohaemoglobin)
• ~ 70% as HCO3-

Question 30

• CO2 dissociation curve
is more linear, and never
reaches .

Answer 30

saturation

Question 31

• CO2 content is

increased with

Answer 31

desaturation of Hb
(Haldane effect)
!

Question 32

• CO2 content of whole

blood is ≈ _______ O2 content

Answer 32

3 x higher

than

Question 33

Blood contains only a small part (~2.5 L) of total CO2 stored in the body:

Answer 33

• Content ~ 0.5 L CO2 Lblood-1 x Total blood volume (~ 5 L)
Total CO2 stored ~100L:
• Much of it dissolved in fat or stored in bone.

Question 34

O2 stores are minute!

~approx?

Answer 34

1.5 L in blood + alveoli + myoglobin.

Question 35

The six important, continuous phases of

respiration include:

Answer 35

1. Bulk flow of air in/out of the lungs (ventilation).
2. O2 and CO2 diffusion between alveoli & blood.
3. O2 transport by blood (bulk flow or convection) to
   the tissues.
4. Release of O2 from Hb & diffusion to cells.
5. Use of O2 by cells & production of waste products
   including CO2.
6. CO2 transport by blood where some diffuses out of
   the blood and is exhaled

Question 36

CO2 is excreted from the BODY by?

Answer 36

body:
• by exhalation
• by micturition