Metabolism is an over-arching term to describe all of the different pathways
involved in energy acquisition and conversion. In this section, we will
introduce one of these specific pathways, the respiratory pathway.
Respiration refers to the acquisition of energy from food. It is a process
common to all
eukaryotic cells. In
studying respiration, we will focus on the metabolic pathways that convert
glucose into ATP. Among the components of the respiratory pathway are
the processes of glycolysis, the citric acid cycle, and oxidative
phosphorylation.
If we think about respiration in day-to-day terms, we immediately think of
breathing and oxygen. From an early age, we learn how crucial oxygen is to our
survival and that breathing is how we obtain oxygen from the air. We will now
begin to see exactly how oxygen plays a role inside our bodies. Using oxygen,
organisms can break down ingested foods more easily through oxidation, an
energetically favorable reaction. However, though oxygen is a vital component
of respiration, respiration can occur without oxygen. Respiration that involves
oxygen is called aerobic respiration while that lacking oxygen is called
anaerobic. Of the two, aerobic respiration is far more efficient, producing
more energy per gram of glucose. We will explore the specifics of how these
processes differ in the coming sections.
The energy gained from glucose breakdown can be used to synthesize ATP, which in
turn can help with the synthesis of other, more complex molecules that would
otherwise be too unfavorable to occur. The
mitochondria is
the main cellular structure involved in respiration.
