Chapter 1-Amino Acids Peptides And Proteins

Question 1

What are the four parts of an amino acid?

Answer 1

1. Amino group
2. Carboxylic acid
3. Hydrogen
4. R group

Question 2

What is the stereo chemistry of the alpha carbon for all chiral amino acids in eukaryotes?

Answer 2

L

Question 3

Which amino acid is the only achiral amino acid?

Answer 3

Glycine

Question 4

All chiral amino acids have what configuration?

Answer 4

S

Question 5

Which chiral amino acid has an R configuration?

Answer 5

Cysteine

Question 6

Amino acids are amphoteric. What is the meaning of amphoteric?

Answer 6

The ability to except or donate protons.

Question 7

How is a peptide bond formed?

Answer 7

Combination of amino acid subunits or residues via a dehydration or condensation reaction.

Question 8

What is a dipeptide?

Answer 8

Two amino acid residues

Question 9

What is a tripeptide?

Answer 9

Three amino acid residues

Question 10

What is an oligopeptide?

Answer 10

A few amino acid residues less than 20.

Question 11

What is a polypeptide?

Answer 11

More than 20 amino acid residues.

Question 12

What makes amide bonds rigid?

Answer 12

Resonance

Question 13

What type of reaction is the breaking of a peptide bond?

Answer 13

Hydrolysis.

Question 14

What types of bonds are associated with primary protein structure?

Answer 14

Peptide bonds.

Question 15

What types of bonds are associated with secondary protein structure?

Answer 15

Hydrogen bonding

Question 16

What types of bonds are associated with tertiary structure?

Answer 16

Hydrophobic, hydrogen, disulfide.

Question 17

What is the primary structure of proteins?

Answer 17

Primary structure of the interaction of individual amino acids. Involves peptide bonding.

Question 18

What is secondary structure of proteins?

Answer 18

Involves alpha helix and beta pleated sheets. Hydrogen bonding holds the structures together.

Question 19

What is tertiary structure of proteins?

Answer 19

The 3-D shape of one polypeptide chain.

Question 20

What is the quaternary structure of proteins?

Answer 20

The interaction of peptides with multiple subunits.

Question 21

Which amino acid can cause kinks in an alpha helix and beta pleated sheets?

Answer 21

Proline because of its rigid cyclic structure

Question 22

What can lead to denaturation?

Answer 22

Extreme heat and increasing solute concentration.

Question 23

What is denaturation?

Answer 23

Loss of 3-D structure of a protein

Question 24

PKa

Answer 24

Ph where 1/2 the species is deprotonated

Question 25

pI

Answer 25

pH where molecule is electrically neutral

Question 26

At low pH are amino acids protonated or deprotonated?

Answer 26

Protonated (positively charged) COOH NH4+

Question 27

At high ph are amino acids protonated/deprotonated?

Answer 27

Deprotonated (negatively charged) COO- NH2

Question 28

Estimation for the pI of an acidic vs basic amino acid

Answer 28

Acidic way less than 6 | Basic way more than 6

Question 29

Formula to calculate for the pI of an acidic amino acid

Answer 29

Average of pKa of the R group and COOH

Question 30

Formula to calculate for pI of a basic amino acid

Answer 30

Average of the pKa of the R group and NH3

Question 31

What is a peptide?

Answer 31

Formed from amino acid subunits/ residues

Question 32

What bond joins together the residues in a peptide?

Answer 32

Peptide bond The electrophilic carbonyl carbon of one amino acid is attacked by the nucleophilic amino group in a second amino acid

Question 33

Peptides drawn and read in what direction?

Answer 33

N to C

Question 34

What things can cause denaturation?

Answer 34

Heat, increasing solute concentration

Question 35

What is denaturation?

Answer 35

Loss of 3D structure

Question 36

Conjugated proteins

Answer 36

Proteins with covalently attached molecules called prosthetic groups

Question 37

What is the effect of placing a hydrophobic side chain in aqueous solution

Answer 37

Hydrogen bonds not able to form with side chain. Water molecules forced to group and bond together. This decreases entropy/disorder (S) of the surrounding water molecules and makes the overall process nonspontaneous (positive delta G)

Question 38

What is the affect of place if a hydrophilic side chain in an aqueous solution?

Answer 38

Hydrogen bonds are able to form with the side chain. Giving water molecules more latitude in their position. This increases entropy/disorder (S) of the surrounding water molecules and makes the overall process spontaneous (negative delta G)

Question 39

Which amino acids are likely found in beta turns of beta pleated sheets?

Answer 39

Histidine and Proline

Question 40

Higher ratio of basic amino acids to acidic amino acids will have a higher/lower pI?

Answer 40

Higher pI