Page 20 - Lesson Notes - Biomolecules 1

are either linear or circular and criss-cross each other, i.e., there are traffic functions.
Flow of metabolites through metabolic pathway has a definite rate and direction and
this metabolic flow is called the dynamic state of body constituents. Also these
metabolic reactions are always catalysed reaction, i.e., no uncatalysed metabolic
conversion is present in living systems. The catalysts which hasten the rate of a
given metabolic conversion are also proteins. These proteins with catalytic power
are called enzymes.
Metabolic Basis for Living
Metabolic pathways in living organisms are divided into two main types
i. Anabolic Pathways
These include the formation of complex structure from simple ones, e.g., formation
of cholesterol from acetic acid, protein synthesis, etc. These are energy consuming
pathways.
ii. Catabolic Pathways
Glycolysis
Glucose is degraded to lactic acid in human skeletal muscle, liberating energy. This
metabolic pathway from glucose to lactic acid which occurs in ten metabolic steps
is called glycolysis.
This liberated energy is stored in the form of chemical bonds and this bond energy
can be utilised in various biosynthetic, osmotic and mechanical work when needed.
Adenosine Triphosphate (ATP)
The most important form of energy currency present in living systems is the bond
energy in a chemical compound of ATP.
The Living State
Various chemical compounds (metabolites or biomolecules) are present at a
concentration characteristic of each of them, i.e., all living organisms exist in a
steady state characterised by concentrations of each of these biomolecules. It is the
most important fact of biological systems. These metabolites are in a state of
metabolic flux. Hence, the living system is kept in a non-equilibrium state by
metabolic flux, which enables it to perform work as living organism.
It has to work continuously and are unable to reach equilibrium.
Therefore, metabolism is helpful in providing a mechanism which enables energy
production.
It can be stated that the living state and . metabolism are synonymous and are
correlated. Thus, metabolism and living state are incomplete without each other.
These include the formation of simpler structures, i.e., the breakage of complex
structures into simpler ones, e.g., Conversion of glucose into lactic acid in skeletal
muscles.