metabolic basis of life biomolecules
Channel: ISHTA’s BIO ACADEMY
Date: 27/02/2023

9.10 METABOLIC BASIS FOR LIVING
Metabolic pathways can lead to a more complex structure from a simpler
structure (for example, acetic acid becomes cholesterol) or lead to a simpler
structure from a complex structure (for example, glucose becomes lactic
acid in our skeletal muscle). The former cases are called biosynthetic
pathways or anabolic pathways. The latter constitute degradation and
hence are called catabolic pathways. Anabolic pathways, as expected,
consume energy. Assembly of a protein from amino acids requires energy
input. On the other hand, catabolic pathways lead to the release of energy.
For example, when glucose is degraded to lactic acid in our skeletal muscle,
energy is liberated. This metabolic pathway from glucose to lactic acid which
occurs in 10 metabolic steps is called glycolysis. Living organisms have
learnt to trap this energy liberated during degradation and store it in the
form of chemical bonds. As and when needed, this bond energy is utilised
for biosynthetic, osmotic and mechanical work that we perform. The most
important form of energy currency in living systems is the bond energy in
a chemical called adenosine triphosphate (ATP).
How do living organisms derive their energy? What strategies have they
evolved? How do they store this energy and in what form? How do they
convert this energy into work? You will study and understand all this under
a sub-discipline called ‘Bioenergetics’ later in your higher classes.
9.11 THE LIVING STATE
At this level, you must understand that the tens and thousands of
chemical compounds in a living organism, otherwise called metabolites,
or biomolecules, are present at concentrations characteristic of each of
them. For example, the blood concentration of glucose in a normal healthy
individual is 4.5-5.0 mM, while that of hormones would be nanograms/
mL. The most important fact of biological systems is that all living
organisms exist in a steady-state characterised by concentrations of each
of these biomolecules. These biomolecules are in a metabolic flux. Any
chemical or physical process moves spontaneously to equilibrium. The
steady state is a non-equilibrium state. One should remember from
physics that systems at equilibrium cannot perform work. As living
organisms work continuously, they cannot afford to reach equilibrium.