BIOL1006 Lecture Notes - Lecture 3: Egg White, Covalent Bond, Pepsin
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Lecture 3
Each protein has its own unique sequence of amino acids
and the interactions between these amino acids create a
specify shape.
This shape determines the protein's function, from
digesting protein in the stomach to carrying oxygen in
the blood.
If the protein is subject to changes in temperature, pH,
or exposure to chemicals, the internal interactions
between the protein's amino acids can be altered, which
in turn may alter the shape of the protein.
Although the amino acid sequence does not change, the
protein's shape may change so much that it becomes
dysfunctional, in which case the protein is considered
denatured.
Pepsin, the enzyme that breaks down protein in the
stomach, only operates at a very low pH. At higher pHs
pepsin's conformation, the way its polypeptide chain is
folded up in three dimensions, begins to change.
The stomach maintains a very low pH to ensure that
pepsin continues to digest protein and does not denature.
Because almost all biochemical reactions require
enzymes, and because almost all enzymes only work
optimally within relatively narrow temperature and pH
ranges, many homeostatic mechanisms regulate
appropriate temperatures and pH so that the enzymes
can maintain the shape of their active site.
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