4-1 PROTEINS: THREE–DIMENSIONAL STRUCTURE AND FUNCTION
Introduction

The primary structure of proteins is the linear _______________ of amino acid residues
in a polypeptide.

Polypeptide chains do not have linear conformations, but contain _______________,
_______________, _______________, and _______________.

Recall that in order to change conformation, a _______________ bond must be broken.
Also recall that each amino acid can exist in ___ and ___ conformations, and since there
are many _______________ in a protein, there is an _______________ number of
potential conformations.

Under physiological conditions, each protein _______________ into a single stable shape
known as its _______________ conformation.
o The biological _______________ of a protein depends completely on its native
conformation.

Rotation around covalent bonds is restricted by _______________ bonds and other weak
_______________ between amino acid residues.
Protein Size

A protein may be a _______________ polypeptide chain, or it may be composed of
_______________ polypeptide chains bound to each other by _______________
interactions.

In general, each polypeptide chain is encoded by a single _______________, but there
are exceptions.

In some species, the _______________ and _______________ of every polypeptide can
be determined from the sequence of the _______________.
Types of Proteins

Many proteins are _______________ proteins, which are __________ - soluble,
_______________, roughly _______________ macromolecules whose polypeptides are
tightly _______________.
o The interior is _______________ and the surface is _______________.
o They possess _______________ or indentations that specifically recognize and
bind other compounds.
o Many are _______________, _______________ proteins, and _______________
proteins.

Polypeptides can be _______________ components of large subcellular or extracellular
structures.
o _______________ proteins are structure proteins that provide mechanical
_______________ to cells or organisms. They are typically large cables or
threads.
o Examples:

-keratin, the major component of __________ and __________.

Collagen, the major component of __________, __________,
__________, and __________.

Many proteins are integral components of _______________, or they are somehow
associated with them.