Chapter 4.2.1 Large protein molecules contain more than one polypeptide chain.

Noncovalent bonds.

Any region on a protein's surface that interacts with another molecule through sets of noncovalent bonds.

Subunit.

• Two protein subunits.
• They are made by two identical protein subunits having the same binding sites and binding to each other. they are found in bacterial cells.

Hemoglobin.

Two alpha globin and two copies of beta globin.

Carry oxygen and they carry four.

Symmetrically.

Large protein molecules often have more than one polypeptide chain.

Filaments, sheets, or spheres.

By the binding site on one protein molecule being complementary to another region on the surface of another protein molecule of the same type.

Because each protein molecule is bound to its neighbor in an identical way and can extend indefineitely in either direction. Forming an extended protein filament such as actin.

Identical protein subunits.

Other sets of identical proteins associate to form tubes, microtubules of the cytoskeleton.

Globular

Fibrous proteins.

alpha-keratin

A dimer of two identical subunits, with the long alpha helices of each subunit forming a coiled-coil having their ends capped by globular domains with binding sites allowing them to turn into the intermediate filaments.