Chapter 2 : Proteins

Question 1

What are proteins

Answer 1

A molecule composed of amino acids joined together by peptide bonds

Question 2

How many amino acids are there in total

Answer 2

20

Question 3

What is the basic monomer of proteins

Answer 3

amino acids

Question 4

What are the three major groups of an amino acid ?

Answer 4

amino group (NH2) , carboxyl group ( COOH) and the side chain

Question 5

What group gives the identity of the amino acid

Answer 5

the side chain

Question 6

What kind of shape do amino acids have ?

Answer 6

tetrahedral shape

Question 7

True or false , the central carbon on an amino acid is not chiral

Answer 7

False , the central carbon is chiral

Question 8

What are the two enantiomers of all amino acids ?

Answer 8

L and D

Question 9

Between the L and the D isomer, which one is mostly found in proteins

Answer 9

The L isomer

Question 10

How many different types of amino acids are there?

Answer 10

5

Question 11

Non-polar Aliphatic Amino acids

Answer 11

• Nonpolar
• Water insoluble ( CH bonds)
• 7 amino acids

Question 12

Aromatic Amino Acids

Answer 12

• Contain an aromatic group
• nonpolar
• Able to absorb UV light
• 2 amino acids

Question 13

Polar Uncharged Amino Acids

Answer 13

• Contain polar bonds ( OH, SH, or NH)
• contain no charges
• more soluble in water
• 6 amino acids

Question 14

Acidic Amino Acids

Answer 14

• side chain is a COOH group
• weak acids but exist as COO- at neutral pH
• 2 amino acids

Question 15

Basic Amino Acids

Answer 15

• Contain net positive charges at neutral pH
• contain amine group as side chain which is protonated
• 3 amino acids

Question 16

How many dissociable hydrogens does every amino acid have AT LEAST ?

Answer 16

2 hydrogens

Question 17

pK1

Answer 17

1/2 of the amino acid molecules have lost H from the COOH

- falls between pH of 2.0-2.4

Question 18

pK2

Answer 18

1/2 of amino acid molecules have lost H+ from NH3 group

- falls between pH of 9.0-9.8

Question 19

Where do peptide bonds form?

Answer 19

Between the carboxyl group of the 1st aa and the amine group of the 2nd amine

Question 20

What is a biproduct of a peptide bond

Answer 20

water, dehydration synthesis

Question 21

True or False, the peptide bond is a single bond which has resonance form in a double bond

Answer 21

True, the double bond inhibits rotation creating stability and polarity in the protein backbone

Question 22

How many levels of protein structure are there ?

Answer 22

4

Question 23

Primary structure

Answer 23

sequence of amino acids

Question 24

Secondary structure

Answer 24

hydrogen bonding between adjacent amino acids to create α-helix or β-pleated sheet

Question 25

Teritary structure

Answer 25

complete 3D shape of the polypeptide chain

Question 26

Quarternary structure

Answer 26

structure that results after two or more interacting polypeptide chains come together

Question 27

True or false, the primary structure contains all the info for the final 3D shape

Answer 27

True

Question 28

True or false, the backbone of the protein is 3D

Answer 28

False, the backbone of a protein is planar

Question 29

α-Helix

Answer 29

- found in secondary structure - All H bonds are parallel to the axis - helices can be right or left handed

Question 30

β –pleated sheet

Answer 30

- formed from the protein backbone - can either be parallel or antiparallel - side chains extend out perpendicularly

Question 31

β-turn

Answer 31

When the β-sheet is formed , the turn allows fo the backbone to bend, turn or reorient

Question 32

Hydrophobic protein interactions

Answer 32

Nonpolar side chains cluster to avoid interaction resulting in protein folding

Question 33

Ionic protein interactions

Answer 33

Attractions or repulsions between opposite or like charges on the side chains

Question 34

Van Der Waal protein interactions

Answer 34

- quick dipole-dipole reactions resulting in fluctuations in electron distribution

Question 35

Denaturation

Answer 35

the process which protein function begins to degrade due to the surrouding eniorment