Heat Production, Oxygen Consumption and Temperature in Poikilotherms 89
is to CO 2 , H 2 0 and N 2 . Some other amino acids have higher oxygen/heat
equivalences but almost all dietary substances lie between 4.5 and 6.0 cal.
The rate of oxygen consumption is a measure of the activity of the oxidation systems in the cells of an organism. The rate of heat production on
the other hand is the sum of the enthalpy changes (ilH) for all the reactions
going on in the cells. Each measures a somewhat different aspect of metabolism. One of the weaknesses of the present experiments is that they were
not measured simultaneously. Respiration in the Warburg flask may not
have been quite the same as in the calorimeter. This, together with such
factors as the possible intermittent use of oxygen or the repayment of
temporary oxygen debts may account for the low value obtained with
Limnaea. The high value for Lumbriculus is almost certainly due to some
anaerobic breakdown of substrates.
In the yeast experiments the values tended to be lower with increasing
temperature. Here the main energy source was glucose and should have
given a value of 5. This was only attained in the 20 0 experiments. The
explanation of the lower values at the other temperatures is not known but
could possibly be ascribed to side reactions. There are grounds for thinking
that the very low results at 25.8° were due to a slight settlement of cells
which may have occurred in the experiments at this temperature. Other
authors [7] have found that when the pattern of metabolism of an organism
is accurately known agreement is very good between expected and observed heat productions.
References
1. BLAXTER, K. L.: The energy metabolism of ruminants. London: Hutchinson
1962.
2. BRODY, S.: Bioenergetics and growth. New York: Reinhold 1945.
3. DAVIES, P. M. c.: Ph. D thesis University of Dublin 1965.
4. MEYERHOF, 0.: Biochem. Z. 35, 280 (1911).
5. - Pfltigers Arch. ges. Physiol. 146, 159 (1912).
6. RUBNER, M.: Z. BioI. 30, 73 (1894).
7. SENEZ, J. G., and J. P. BELA'ICH: Colloques Internationaux du Centre National
de la Recherche Scientifique. Marseille 1963. No. 124, 357.
Discussion
WOODSTOCK:
1 wish to ask you two questions: (1) Was respiration also measured as CO 2
production? Oxygen uptake might also have occurred by non-respiratory
reactions. (2) Were P /0 ratios determined to estimate the efficiency of
respiration in producing A TP? If A TP production were uncoupled from
respiration, how would this affect the conversion factor between respiration
and heat production?
is to CO 2 , H 2 0 and N 2 . Some other amino acids have higher oxygen/heat
equivalences but almost all dietary substances lie between 4.5 and 6.0 cal.
The rate of oxygen consumption is a measure of the activity of the oxidation systems in the cells of an organism. The rate of heat production on
the other hand is the sum of the enthalpy changes (ilH) for all the reactions
going on in the cells. Each measures a somewhat different aspect of metabolism. One of the weaknesses of the present experiments is that they were
not measured simultaneously. Respiration in the Warburg flask may not
have been quite the same as in the calorimeter. This, together with such
factors as the possible intermittent use of oxygen or the repayment of
temporary oxygen debts may account for the low value obtained with
Limnaea. The high value for Lumbriculus is almost certainly due to some
anaerobic breakdown of substrates.
In the yeast experiments the values tended to be lower with increasing
temperature. Here the main energy source was glucose and should have
given a value of 5. This was only attained in the 20 0 experiments. The
explanation of the lower values at the other temperatures is not known but
could possibly be ascribed to side reactions. There are grounds for thinking
that the very low results at 25.8° were due to a slight settlement of cells
which may have occurred in the experiments at this temperature. Other
authors [7] have found that when the pattern of metabolism of an organism
is accurately known agreement is very good between expected and observed heat productions.
References
1. BLAXTER, K. L.: The energy metabolism of ruminants. London: Hutchinson
1962.
2. BRODY, S.: Bioenergetics and growth. New York: Reinhold 1945.
3. DAVIES, P. M. c.: Ph. D thesis University of Dublin 1965.
4. MEYERHOF, 0.: Biochem. Z. 35, 280 (1911).
5. - Pfltigers Arch. ges. Physiol. 146, 159 (1912).
6. RUBNER, M.: Z. BioI. 30, 73 (1894).
7. SENEZ, J. G., and J. P. BELA'ICH: Colloques Internationaux du Centre National
de la Recherche Scientifique. Marseille 1963. No. 124, 357.
Discussion
WOODSTOCK:
1 wish to ask you two questions: (1) Was respiration also measured as CO 2
production? Oxygen uptake might also have occurred by non-respiratory
reactions. (2) Were P /0 ratios determined to estimate the efficiency of
respiration in producing A TP? If A TP production were uncoupled from
respiration, how would this affect the conversion factor between respiration
and heat production?