Biology Times (^) March 19
(ii) When fats are used in respiration, the R.Q is less
than 1.
Eg: Germination of fatty acids, eg: castor seeds,
rape seed.
(iii) When proteins are respiratory substrates the
ratio would be about 0.9.
(iv) R.Q. value is more than one: When
aerobic respiration uses
organic acids as respiratory substrates.
(v) R.Q value is infinity: In case of anaerobic
respiration where CO 2 is evolved but O 2 is not
consumed.
Eg: alcoholic fermentaion.
(vi) R.Q value is zero: It is found in case where
oxygen is consumed but CO 2 is not evolved. Eg:
In succulent plants (e.g: Opuntia)[CO 2 produced
during respiration is fixed internally for use in
photosynthetic activity during the day]
Importance of R.Q:
m It gives information about types of respiration
i.e., aerobic or anaerobic.
m The types of respiratory substrates can be known.
m Normal nutrition or starvation condition can be
known.
m Food transformation like synthesis of fats or
conversion of fats into carbohydrates can be
known.
Pasteur effect:
The inhibitory effect of oxygen (aerobic
condition) on glycolysis i.e., pasteur effect was
discovered by Louis Pasteur, while studying
fermentation by yeast.
In aerobic condition, the levels of glycotylic
intermediates from fructose - 1, 6 - bisphosphate
onwards decreases, while the earlier intermediates
accumulates. This clearly indicated that pasteur
effect is due to the inhibition of the enzyme
phosphofructokinase.
The Pacemaker of respiration is the enzyme
phosphofructo kinase (PFK) is also an
allosteric enzyme, which is inhibited at a higher
concentration of ATP.Inhibitors of Krebs’s cycle:
Inhibitors of terminal oxidation:
m NADH dehydrogense is inhibited by rotenone,
amytal, piercidin A and block ETS in the span
between NADH and ubiquinone.
m Antimycin A- blocks electron transfer from
cytochrome to b to c.
m Hydrogen cyanide, hydrogen sulphide and carbon
monoxide which block electron transport from
cytochrome a - a 3.Certain compounds that can delink the electron
transport from oxidative phosphorylation such
compounds, known as uncouples, increases the
permeability of inner mito chondrial membrane
to protons(H+). As a result ATP synthesis does
not occur. The energy linked with the transport of
electrons is dissipated as heat.