Introduction to Proteins

Question 0

pH =

Answer 0

-log [H+]

[H+] = 10^(-pH)

Question 1

pH is the measure of the amount of _________ in a solution

Answer 1

hydrogen ions

Question 2

Amino acids each contain a central carbon surrounded by what four things?

Answer 2

• a carboxyl group (C=O)
• an amino group (N-)
• a hydrogen atom
• an R group (as simple as H, or C chains)

Question 3

What are the two functional groups of amino acids?

Answer 3

the carboxyl group and amino group

Question 4

The side group, R group are divided into what four types of side chains?

Answer 4

polar, nonpolar, acidic, and basic

Question 5

Aspartate and Glutamate are classified as: polar, nonpolar, acidic, or basic?

Answer 5

acidic

Question 6

Arginine, Histidine, and Lysine are classified as: polar, nonpolar, acidic, or basic?

Answer 6

Basic

Question 7

Asparagine, Cysteine, Glutamine, Serine, Threonine, and Tyrosine are classified as: polar, nonpolar, acidic, or basic?

Answer 7

Polar

Question 8

The sequence of amino acids makes up what structure of a protein?

Answer 8

primary

Question 9

Are nonpolar substances hydrophobic or hydrophilic?

Answer 9

Hydrophobic

Question 10

Are polar substances hydrophobic or hydrophilic?

Answer 10

Hydrophilic

Question 11

Define amphiphilic

Answer 11

Substances that are both polar and nonpolar

Question 12

The secondary structure of proteins is described as what?

Answer 12

The initial folding of the amino acid chain (polypeptide)

Question 13

What are the two structures an amino acid chain can fold into?

Answer 13

This would be secondary protein structure; amino acid chains can fold into ALPHA-HELICES or BETA SHEETS (pleated).

Question 14

Alpha helices twist and form due to what bond?

Answer 14

Hydrogen bonding between carbonyl and mide groups.

Question 15

Why is proline not found in the alpha helix?

Answer 15

Because the nitrogen of proline is bound to two carbons and has a limited ability to rotate.

Question 16

In an alpha helix, where do the side chains, carbonyl groups, and amide groups face?

Answer 16

Carbonyl and amide groups face towards the inside of the helix. Side chains face the outside.

Question 17

In beta pleated sheets, hydrogen bonding also occurs between the carbonyl and amide groups, but the ________ are stretched out and bonding occurs along the _______ of the chain.

Answer 17

In beta pleated sheets, hydrogen bonding also occurs between the carbonyl and amide groups, but the POLYPEPTIDES are stretched out and bonding occurs along the LENGTH of the chain.

Question 18

Define tertiary structure of proteins.

Answer 18

Remember, primary is the lining up of the amino acids, secondary is the initial folding of the amino acid chain.
Tertiary structure is how the protein (either in alpha helix or beta pleated sheet form) further folds in on itself. It does this to hide the hydrophobic regions and expose hydrophilic ones.

Question 19

In regards to protein structure, which structure functions to hide the hydrophobic regions and expose the hydrophilic ones?

Answer 19

Tertiary structure

Question 20

Quaternary structure involves the interaction of multiple proteins. What are some possible ways these proteins are held together?

Answer 20

• hydrogen bonding
• disulfide bridges
• salt bridges
• hydrophobic forces
  Note that not all proteins have a quaternary structure (Hemoglobin does, Myoglobin does not)

Question 21

What are cofactors?

Answer 21

Cofactors are elements (organic or inorganic) that help an enzyme to catalyze a reaction.
They are necessary for the enzyme to perform its job.

Question 22

What are two types of cofactors?

Answer 22

Coenzymes and Prosthetic Groups

Question 23

How do coenzymes (a type of cofactor) work?

Answer 23

Coenzymes work with the enzyme, but are not covalently attached, to catalyze a reaction

Question 24

How do prosthetic groups (a type of cofactor) work?

Answer 24

Prosthetic groups are covalently bonded to an enzyme.

Question 25

What are isoenzymes?

Answer 25

Isoenzymes are enzymes that catalyze the same reaction, but they have a different physical and chemical pathway for doing so. They may be found in different parts of the cell or in different tissues.