Energy Metabolism I -measuring metabolic rate -factors influencing VO2

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DPG (2,4 diphosphoglycerate) has little effect

Fetal Hb

3

Q. Is RBC count always the same?

myoglobin

hyperbolic curve

sigmoid curve

6

Q. How are leaks plugged?

7

Leukocyte

Erythrocyte (RBC) platelet

Clotting

8

Haemophilia: loss of critical clotting factors leads to uncontrolled bleeding (rare recessive trait that most often affects males)

9

Sickle cell anemia

-1M deaths/yr-10% of population infected by malaria-90% of casesare in sub-Saharan Africa

Normal RBCs are particularly susceptible

Heterozygotes for Hb-SA (‘sickle-cell trait’) are less vulnerable.

Energy Metabolism

C6H12O6 + 6 O2 --> 6 CO2 + 6 H2O + 38 ATP + ‘heat’ glucose (oxidative phosphorylation)

heat released from food/unit time

energy metabolism/unit time = metabolic rate kcal/hr kJoules/hr (1 kcal = 4.184 kJ) watts (1 watt = 1 Joule/sec) (weight specific) kcal/kg . hr kJ/kg . hr

basal metabolic rate (BMR) - endotherms at rest standard metabolic rate - ectotherms at rest (specify temperature)

How can we measure metabolic rate in a whole animal?

C6H12O6 + 6 O2 --> 6 CO2 + 6 H2O + 38 ATP + ‘heat’ glucose

1) Calculate difference between energy content of food (Kcal) and energy content of waste products (material balance)

Q: Problems?

Antoine Lavoisier 1743-1794

calorimeter

ice

2) Measure total heat production (direct calorimetry)

1919

3) Respiratory gas exchange (indirect calorimetry)

C6H12O6 + 6 O2 --> 6 CO2 + 6 H2O + 38 ATP + ‘heat’ glucose

. VO2

ml O2/g . hr

4.8 kcal released/ liter of O2 consumed

a) Measure rate of oxygen consumption

closed respirometry

aquatic animals

open respirometry

respiratory conformers respiratory regulators

air-breathing animals

closed respirometry

spirometer (closed system)

Antoine Lavoisier

spirometer

open respirometry (air breathers)

1784

Q: what is the problem with using O2 consumption as a measure of metabolism during exercise?

Q: what is the problem with using O2 consumption as a measure of metabolism during exercise?

b) Measure rate of CO2 production

C6H12O6 + 6 O2 --> 6 CO2 + 6 H2O + 38 ATP + ‘heat’ glucose

2) exhaled [CO2] too variable; may not reflect metabolic rate

BUT: 1) amount of heat produced per unit of CO2 released varies more with diet

RQ = 1

obtain metabolic rates of whole animals in the field??

doubly labeled water technique:

a) inject tritium (3H) and oxygen 18 (18O)

b) wait several hours or days

c) collect blood sample, and measure depletion of 3H and 18O

--decline in [18O] relates to rate of CO2 and water loss --decline in [3H] relates to rate of water loss

What factors influence metabolic rate in whole animals??

ml O2/hr ?

ml O2/hr

ml O2/g . hr