Chapter 4 - Amino Acids

Question 1

proteins

Answer 1

• biological macromolecules that act as enzymes, hormones, receptors, channels, transporters, antibodies, and support structures inside/outside cells - composed of 20 different amino acids uniquely linked together

Question 2

amino acids

Answer 2

• 20 distinct molecules - building blocks of proteins - alpha amino group, carboxyl group, tetrahedral carbon, and variable R-group

Question 3

3 chemical properties of amino acids

Answer 3

• shape - ability to hydrogen bond - ability to act as an acid or base

Question 4

acidic amino acids

Answer 4

• aspartic acid (Asp, D) - glutamic acid (Glu, E) - histidine (His, H)

Question 5

basic amino acids

Answer 5

• lysine (Lys, K) - arginine (Arg, R) - histidine (His, H)

Question 6

hydrophobic (aliphatic) amino acids

Answer 6

• glycine (Gly, G) - alanine (Ala, A) - valine (Val, V) - leucine (Leu, L) - isoleucine (Ile, I) - methionine (Met, M)

Question 7

hydrophobic (aromatic) amino acids

Answer 7

• phenylalanine (Phe, F) - tryptophan (Trp, W)

Question 8

hydrophobic amino acids are found on the _____

Answer 8

interior of folded globular proteins, away from water

Question 9

polar amino acids do not ____

Answer 9

act as acids or bases

Question 10

hydrophilic amino acids

Answer 10

• serine (Ser, S) - threonine (Thr, T) - tyrosine (Tyr, Y) - aromatic - asparagine (Asn, N) - glutamine (Gln, Q) - cysteine (Cys, C)

Question 11

proline

Answer 11

• hydrophobic - amino group covalently bound to its non-polar side chain - secondary alpha-amino group - distinctive ring structure

Question 12

sulfur-containing amino acids

Answer 12

• cysteine (thiol or sulfhydryl) - methionine (thioether)

Question 13

nine essential amino acids

Answer 13

• lysine - histidine - threonine - valine - leucine - isoleucine - phenylalanine - tryptophan - methionine

Question 14

lysine and arginine are _____

Answer 14

protonated at physiological pH

Question 15

acidic functional groups in acidic amino acids

Answer 15

• two backbone groups - R-group

Question 16

important modification in serine, threonine, and tyrosine

Answer 16

• hydroxyl group attaches with a phosphate group by kinase - changes structure, regulates protein activity

Question 17

zwitterion

Answer 17

• balanced positive and negative charges on a molecule - dipolar

Question 18

isoelectric point

Answer 18

pH where molecule is uncharged (zwitterionic)

Question 19

if pH of solution is lower than pKa then the group will mostly be in its ____

Answer 19

protonated form

Question 20

if pH of solution is higher than pKa then the group will mostly be in its ____

Answer 20

de-protonated form

Question 21

peptide bonds

Answer 21

• covalent bonds that link amino acids together - between carboxyl group & amino group - loss of water

Question 22

disulfide bridges

Answer 22

• covalent bonds that link cysteine R-groups - thiol-thiol bond (oxidized)

Question 23

what is the pattern formed that is known as the backbone?

Answer 23

N-C-C-N-C-C

Question 24

residue

Answer 24

individual amino acid when it is part of a polypeptide chain

Question 25

proteolysis or proteolytic cleavage

Answer 25

hydrolysis of a protein by another protein

Question 26

proteolytic enyzme or protease

Answer 26

does the cutting or cleavage of peptide bonds

Question 27

what structure does disulfide bridging play an important role in?

Answer 27

tertiary

Question 28

cystine

Answer 28

disulfide bonded cysteines

Question 29

denatured proteins are ____

Answer 29

non-functional

Question 30

denaturation

Answer 30

disruption of a protein’s shape without breaking peptide bonds

Question 31

urea

Answer 31

• denatures proteins - disrupts hydrogen bonding interactions - pH, temp, & changes in salt concentration

Question 32

primary structure

Answer 32

• linear ordering of amino acid residues - peptide bonds determine the structure

Question 33

secondary structure

Answer 33

• initial folding of a polypeptide chain into shapes stabilized by hydrogen bonds between NH & CO groups - alpha-helix & beta-pleated sheet

Question 34

alpha-helices are always ____

Answer 34

right-handed

Question 35

problems with proline bonding

Answer 35

• peptide bonding eliminates the only hydrogen on the amino group which disrupts hydrogen bonding - forced to kink the polypeptide chain

Question 36

proline residues never appear within the ____

Answer 36

alpha-helix

Question 37

alpha-helix

Answer 37

• favorable structure for a hydrophobic transmembrane region (polar NH & CO groups inside of helix) - hydrophobic R-groups radiate out of helix

Question 38

beta-pleated sheet

Answer 38

• stabilized by hydrogen bonding between NH & CO groups - bonding occurs from distant or different chains - extended & can be parallel or antiparallel

Question 39

tertiary structure

Answer 39

interactions between amino acids residues located distantly from each other

Question 40

driving force of secondary to tertiary

Answer 40

• interactions of R-groups w/ each other & solvent (water) - hydrophobic R-groups tend to fold into the interior protein (opposite for polar R-groups)

Question 41

hydrogen bonding would not affect ____

Answer 41

primary structure

Question 42

quaternary structure

Answer 42

interactions between polypeptide subunits

Question 43

subunit

Answer 43

single polypeptide chain that is part of a large complex containing multiple subunits