L.1 Amino Acids & Protein (2)

Question 1

How many amino acid residues does a _____ have?

dipeptide?

tripeptide?

oligopeptide?

polypeptide?

Answer 1

1. 2
2. 3
3. 20 or less
4. more than 20

Question 2

Forming a peptide is a ________ or _________ reaction.

Answer 2

Condensation or dehydration (releasing a water molecule)

Question 3

In a peptide bond formation, what molecule is the nucleophile?

What kind of bond is formed?

Answer 3

The nucleophilic amino group of one amino caid attacks the electrophilic carbonyl of the other amino acid.

The new amide bond is rigid because of resonance.

Question 4

Breaking a peptide is a ________ reaction.

Answer 4

Hydrolysis

Question 5

What is the primary structure of a protein?

What are the stabilizing bonds?

Answer 5

Linear sequence of an amino acid chain.

Peptide bond (covalent)

Question 6

What is the secondary structure of a protein?

What are the stabilizing bonds?

Answer 6

Local structure determined by nearby amino acids

Alpha helices

and

Beta-pleated sheets

(can be parallel and anti-parallel)

Proline can interrupt secondary structure

because of its rigid cyclic structure

Hydrogen bonds.

Question 7

What is the tertiary structure of a Protein?

What are the interactions?

Answer 7

3D-Shape

Hydrophobic Interactions

Acis/base interactions

Disulfide salt bridges/links

(When two cysteine molecules are oxidized and create a covalent bond with each other creating cystine)

Question 8

What is the quaternary structure of proteins?

Answer 8

Interactions between separate subunits

of a multisubunit protein

(Conjugated Proteins)

Question 9

What is a prosthetic group?

Answer 9

Proteins with covalently attached molecules are called conjugated proteins.

These molecules are called prosthetic groups.

• metal ion*
• vitamin*
• lipid*
• carbohydrate*
• nucleic acid*

Question 10

What are the names of the conjugated proteins that hold a ________ prosthetic group?

Lipid?

Carbohydrates?

Nucleic Acid?

Answer 10

Lipoprotein

Glycoprotein

Nucleoprotein

Question 11

Why are quaternary structures in proteins favorable?

Answer 11

1. Lower qty of DNA
2. Catalytic sites of multiple units are closer together.
3. Cooperativity or allosteric effects.

Question 12

What two things can cause denaturation in a protein?

Answer 12

Increasing heat and increasing Solute!

Question 13

Why do hydrophobic regions of proteins fold inward?

Answer 13

Entropy!

Water cannot form bonds with hydrophobic molecules,

thus they arrange in a specific form to maximize their bonds, this increases entropy and is unfavorable.