Video Transcript
Before lipids can be absorbed into the villi of the small intestines, they must be
broken down into fatty acids and glycerol molecules. What type of metabolic reaction, anabolism or catabolism, is this an example of?
This question introduces a lot of important terminology. So let’s start off by defining some of these key terms.
To begin, what is a metabolic reaction? Each metabolic reaction in our bodies contributes to our individual metabolism, which
describes all the chemical reactions that occur within us to maintain life.
There are two main types of metabolic reaction: anabolic reactions and catabolic
reactions. Anabolism requires an input of energy, which is supplied by a molecule called ATP, to
form bonds and construct larger molecules from individual smaller units. On the other hand, catabolism involves the breaking of bonds in large molecules to
produce smaller molecules. This process releases energy that is stored in the form of ATP.
As the question mentions, lipids are fairly large molecules that are too big to be
absorbed across the wall of the small intestine. As a result, they first need to be broken down into their constituent subunits. These subunits are fatty acids and glycerol molecules. As lipids are broken down into glycerol and fatty acids, this is an example of a
catabolic reaction. So the type of metabolic reaction this is an example of is catabolism.
