Cell Bio Quiz 3

Enzymes act by

decreasing activation energy.

In the fluid mosaic model of biological membrane structure, transmembrane proteins are

embedded nearly randomly in the lipid bilayer.

Phospholipids consist of a 3-carbon core to which two fatty acids and a phosphate group are linked. The most common 3-carbon core is

glycerol

Lipids with unsaturated fatty acids

increase fluidity of membranes.

Introducing a double bond into a fatty acid puts a(n) _______ into the conformation of the molecule.

kink

The coenzymes NAD+ and NADP+ are structurally related to the vitamin

niacin

Proteins must have more than one _______ to have a quaternary structure.

polypeptide chain

Which class of molecule accelerates transport across biological membranes?

proteins

The α (alpha) helix is an example of which level of protein structure?

secondary

What is the major carbohydrate-storage molecule in plants?

starch

Passive transport across a membrane refers to

transport in the energetically favorable direction.

Which of the following bases is not found in DNA?

uracil

Chymotrypsin, trypsin, elastase, and thrombin are all members of the serine protease family because each

uses the same catalytic mechanism involving the same key amino acids.

Coenzymes are chemically related to

vitamins

The most abundant molecule in cells is

water

The three-dimensional structure of a protein is analyzed most definitively by

x-ray crystallography

How many amino acids are commonly incorporated into proteins?

20

Enzymes affect the transition state of a chemical reaction by

All of the above

What is the effect of a β barrel on the permeability of a membrane?

It increases permeability.

Molecules that are partly water-soluble and partly water-insoluble are

amphipathic