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Honors Biology
Protein Structure Homework- KEY
1. What is the primary structure of a protein?
The primary structure of a protein is the order of the linked amino acids.
2. Of the 20ish amino acids humans need to make their proteins, some are called essential
amino acids. Humans have lost the ability to make these amino acids themselves, and
must eat other life forms to get them. List the essential amino acids. You may have to
use other resources to find the answer to this question.
The essential amino acids for humans are tryptophan, methionine, threonine,
valine, phenylalanine, lysine, isoleucine, and leucine.
3. Secondary structures of proteins are very important to the protein’s function. There are
two main types…please describe them.
Alpha helices (α helices) occur when the amino acids in a section of protein coil
into a spiral. Beta sheets (β sheets) occur when amino acids in a section of
protein fold into accordion pleats.
4. Tertiary structure of proteins is the complete 3-D shape of the entire protein. Below is
the tertiary structure of two human proteins. Look at the structures, and identify the
secondary structures present in each. There should be two structures present in the
structure on the right.
5. Denaturation is a leading cause of protein death. Define denaturation.
A protein denatures when it changes shape or unfolds.
Describe two ways to denature a protein.
Proteins can denature from
 Changes in temperature, particularly heating
 Changes in salt (ion concentrations)
 Changes in pH
 Direct unfolding by a toxin