Biochem- Ch 1

Question 1

Amino acids

Answer 1

Four groups attached to alpha C

• amino group
• H
• carboxylic group
• R group

-20 aa appear in proteins of eukaryotes

Question 2

R group

Answer 2

Determines chemistry and function of the amino acid

Question 3

Stereochemistry of aa

Answer 3

• L aa are naturally occurring
• all aa except Cysteine have S configuration
• all chiral except glycine

Question 4

Side chains

Answer 4

Nonpolar, nonaromatic
Aromatic
Polar
Negatively charged (acidic)
Positively charged (basic)

Question 5

Nonpolar and nonaromatic (7)

Answer 5

Glycine
Proline 
Alanine
Leucine
Isoleucine 
Valine
Methionine

Question 6

Aromatic

Answer 6

Phenylalanine
Tryptophan
Tyrosine

Question 7

Polar

Answer 7

Cysteine
Serine
Threonine 
Asparginine
Glutamine

Question 8

Acidic

Answer 8

Aspartic acid

Glutamic acid

Question 9

Basic

Answer 9

Lysine
Arginine
Histidine

Question 10

Amphoteric

Answer 10

Aa accept or donate protons

Question 11

Pka

Answer 11

pH at which Half of the species is deprotonated

HA = A-

Question 12

Aa at different pH

Answer 12

Low– aa is fully protonated
pH near pI – aa is neutral zwitterion
High– aa is fully deprotonated

Question 13

pI = isoelectric point

Answer 13

Amino acid without a charged side chain

-calculated by averaging two pka values

Question 14

Aa titration curve

Answer 14

Curve is flat at the pka values of aa

Curve is nearly vertical at pI of aa

Question 15

Oligopeptides

Answer 15

Few aa residues (<20)

Question 16

Peptide bond

Answer 16

Condensation (dehydration) process

-amide bonds = rigid Bc of resonance

Question 17

Hydrolysis

Answer 17

Breaking peptide bond

Question 18

Primary structure

Answer 18

Linear sequence of amino acids in a peptide

-stabilized by peptide bond

Question 19

Secondary structure

Answer 19

Local structure of neighboring aa

-stabilized ny hydrogen bonding Btwn amino and nonadjacent carboxyl groups

Question 20

Secondary structure types

Answer 20

Alpha helix

Beats pleated sheets

Question 21

Alpha helix

Answer 21

Clockwise could around the central axis

• h bonds are vertical
• proline = interrupts structure Bc of its rigid cyclic structure

Question 22

Beta pleated sheets

Answer 22

-rippled strands that can be parallel or antiparallel

Question 23

Tertiary structure

Answer 23

3-D shape of single polypeptide chain

-stabilized by hydrophobic interactions, acid base interactions (salt Bridge), H bonding, and Disulfide bonds

Question 24

Hydrophobic interactions

Answer 24

Push Hydrophobic R groups to the interior of a protein

• increase entropy of surrounding H2O molecules
• creates neg Gibbs free energy

Question 25

Disulfide bonds

Answer 25

Occur when two cysteine molecules are oxidized

-create a covalent bond to form cystine

Question 26

Quaternary structure

Answer 26

Interaction Between peptides in proteins that contain multiple subunits

Question 27

Conjugated proteins

Answer 27

Proteins with covalently attached molecules

Question 28

Prosthetic group

Answer 28

Molecule attached to protein

-can be metal ion, vitamin, lipid, carbohydrate, or nucleic acid

Question 29

Denaturation

Answer 29

Loss of tertiary structure
-caused by heat
Or
Increase solute concentration