Amino Acids

Question 1

Amino acids

Answer 1

Molecules hat contain functional groups amino and carboxyl (COOH)

Question 2

Where is the alpha carbon located on an amino acid?

Answer 2

Next to carboxyl group carbon

Question 3

Parts of amino acid

Answer 3

Amino group
Side chain/R group
alpha carbon
Carboxyl group

Question 4

Which amino acid is achiral?

Answer 4

Glycine

Question 5

Eukaryotes use which form of amino acids?

Answer 5

L-amino acids (counter clockwise)

Question 6

Which amino acid has R absolute configuration?

Answer 6

Cysteine (still an L amino acid)

CH2SH has priority over COOH

Question 7

What amino acids are nonpolar, nonaromatic

Answer 7

Glycine, alanine, valine, leucine, isoleucine, methionine, proline

Question 8

Which amino acid contains sulfur in its side chain & is nonpolar

Answer 8

Methionine

Question 9

Which amino acid has a five member nitrogen ring & is nonpolar- significant effect on structure?

Answer 9

Proline

Question 10

Which amino acid has a methyl group attached to alpha carbon?

Answer 10

Alanine

Question 11

Which amino acids have uncharged aromatic side chains?

Answer 11

Tryptophan, phenylalanine, tyrosine

Question 12

Which amino acid has a double ring and contains nitrogen?

Answer 12

Tryptophan

Question 13

Which amino acid has a benzyl side chain?

Answer 13

Phenylalanine

Question 14

Which amino acid has a benzyl ring plus an -OH group?

Answer 14

Tyrosine

Question 15

Which amino acids have polar side chains?

Answer 15

Serine, threonine, asparagine, glutamine, cysteine

Question 16

Which polar amino acids have -OH side chains that can participate in hydrogen bonding

Answer 16

Serine, threonine

Question 17

Which polar amino acids have amide groups ?

Answer 17

Asparagine & Glutamine

Question 18

What happens to amide side chains when pH changes?

Answer 18

Do not gain or lose protons

Question 19

Which polar amino acid has a thiol group as its side chain?

Answer 19

Cysteine

Question 20

Which is stronger -SH or -OH?

Answer 20

-OH

Question 21

Which is more prone of oxidation -SH or -OH?

Answer 21

-SH

Question 22

Which amino acids are negatively charged/acidic?

Answer 22

Aspartic acid/aspartate & glutamic acid/glutamate

Question 23

What physiological pH of aspartate & glutamate side chains become negatively charged?

Answer 23

pH 7.4

Question 24

Which amino acids are positively charged/basic?

Answer 24

Lysine, arginine, histidine

Question 25

Which amino acid has three nitrogens in its side chain?

Answer 25

arginine

Question 26

Which amino acid has two nitrogens in an aromatic ring?

Answer 26

Histidine

Question 27

Aromatic ring with two nitrogens?

Answer 27

Imidazole

Question 28

pKa of histidine side chain?

Answer 28

pH 6

Question 29

Under physiological pKa what how is histidine protonated?

Answer 29

One nitrogen is protonated and the other isnt

Question 30

How to make an amino acid more positively charged?

Answer 30

Lower pH

Question 31

How to make an amino acid more negatively charged

Answer 31

Increase pH

Question 32

Which amino acids are more hydrophobic?

Answer 32

Alanine, isoleucine, leucine, valine, phenylalanine

Question 33

Which amino acids are hydrophilic?

Answer 33

Histidine, arginine, lysine, glutamnie, aspartate, glutamate, asparagine

Question 34

What is an amphoteric species?

Answer 34

Can accept or release a proton

Question 35

pKa

Answer 35

pH where on average half of the molecule of that species are deprotonated , [HA]={A-}

Question 36

If the pH is less than the pKa?

Answer 36

Majority of species is protonated

Question 37

If pH is greater than pKa?

Answer 37

Majority of species is deprotonated

Question 38

What is the first pKa for?

Answer 38

Carboxyl group

Question 39

What is the carboxylic group pKa?

Answer 39

pH of 2

Question 40

What is the second pKa for?

Answer 40

Amino group

Question 41

What is the pKa of the amino group?

Answer 41

9-10

Question 42

What kind of charge would glycine have at pH 1?

Answer 42

1+

Question 43

What is a zwitterion?

Answer 43

A molecules that have both positive and negative charge, but overall the molecule is electrically neutral.

Question 44

At a pH of 7.4 what kind of charge would glycine have?

Answer 44

0

Question 45

At a pH of 10.5 what kind of charge would glycine have?

Answer 45

-1

Question 46

What happens when pH equals pKa?

Answer 46

The solution will act as a buffer and the line will become more flat

Question 47

Isoelectric point

Answer 47

pH at which the molecule is electrically neutral

Question 48

pI(neutral amino acids)

Answer 48

pKa, NH+ group + pKa COOH / 2 (usually around 6)

Question 49

pI (acidic amino acid)

Answer 49

pKa R group + pKa COOH group / 2

Question 50

pI (basic amino acid)

Answer 50

pKa NH+ group + pKa R group /2

Question 51

What amino acid configuration has groups organized clockwise?

Answer 51

D -configuration

Question 52

What is physiological pH?

Answer 52

pH 7.4

Question 53

Oligiopeptide

Answer 53

Peptide of up to 20 amino acid residues

Question 54

In peptide bond formation, what is the neucleophile?

Answer 54

Amine group

Question 55

In peptide bond formation, what is the electrophile?

Answer 55

Carbonyl group

Question 56

What is kicked off of an amino acid in peptide formation?

Answer 56

Hydroxyl of carboxyl group

Question 57

Where is there partial double bond character in an peptide bond?

Answer 57

From the carbonyl to the C-N bond

Question 58

Where is an amino acid rigid?

Answer 58

On the C-N bond of the amide linkage

Question 59

How are amino acids read from their termini?

Answer 59

N-terminus to C-terminus

Question 60

How is an amino acid broken apart?

Answer 60

Hydrolysis, adding water back into the molecule

Question 61

What is the main kind of bonding involved in secondary structures?

Answer 61

Hydrogen bonding between carbonyl oxygen and amide hydrogen bonds

Question 62

What structure is important in keratin?

Answer 62

a-helices

Question 63

Where do the R groups point in B-pleated sheets?

Answer 63

Above and below the sheet

Question 64

Where is proline often found?

Answer 64

In between chains of B-pleated sheet and start of a-helices

Question 65

What interactions occur during tertiary structures?

Answer 65

R groups- Hydrophobic, hydrophilic interactions, cystine bonds

Question 66

What causes loops in the protein chain?

Answer 66

Disulfide bonds (oxidation)

Question 67

When hydrophobic side chains group together and form a group, what is the effect on entropy & spontaneity?

Answer 67

Negative effect, more order & less disorder & is non-spontaneous

Question 68

When hydrophilic side chains group together and form a group, what is the effect on entropy & spontaneity?

Answer 68

Entropy increases and it is spontaneous

Question 69

Examples of tertiary structures?

Answer 69

Hemoglobin & antibodies

Question 70

Effects of tertiary structures

Answer 70

Reduce SA & increase stability Reduce DNA needed to encode protein Bring catalytic sites close together Cooperativity/allosteric effects

Question 71

Two main causes of denaturation?

Answer 71

Heat and solutes

Question 72

What are reasons for conjugating proteins

Answer 72

1. ) Direct delivery to particular organelle 2. )Direct delivery to cell membrane 3. ) Add cofactor needed for activity

Question 73

Which amino acids have chiral side chains?

Answer 73

Theronine & Isoleucine

Question 74

What can strong base do to proteins?

Answer 74

Denature them by cleaving peptide residues through hydrolysis

Question 75

What is the charge on a cathode?

Answer 75

Negative

Question 76

What is the charge on the anode?

Answer 76

Positive