Nutrition Science and Everyday Application - beta v 0.1

PROTEIN STRUCTURE 317
in cooked foods are at least partially denatured from the heat of cooking, and denaturation
in the stomach is an important part of protein digestion, as we’ll discuss later in this unit.
We can see everyday examples of denaturation in cooking techniques, like how egg whites
become solid and opaque with cooking, and cream becomes fluffy when it’s whipped. Both
of these are examples of denaturation leading to physical changes in protein structure, and
because protein structure determines function, denaturation also causes proteins to lose
their function.
VIDEO: “Heat Changes Protein Structure,” by Sumanas (2006), 1:22 minutes. You can learn more
about denaturation in this video animation.
SHAPE DETERMINES FUNCTION
An important concept with proteins is that SHAPE determines FUNCTION. A change in the
amino acid sequence will cause a change in protein shape. Each protein in the human body
differs in its amino acid sequence and consequently, its shape. The synthesized protein is
structured to perform a particular function in a cell. A protein made with an incorrectly
placed amino acid may not function properly, and this can sometimes cause disease. An
example of this is sickle cell anemia, a genetic disorder. Below is a picture of hemoglobin,
a protein with a globular three-dimensional structure. When packed in red blood cells to
deliver oxygen, this structure gives red blood cells a donut shape.