Amino Acids and Peptides

Question 1

popular amino acid salt seasoning or food flavor enhancer in many Asian countries especially in East and Southeast Asia

Answer 1

monosodium glutamate

Question 2

Discovered by Japanese chemist Kikunae Ikeda in 1908

Answer 2

MSG

Question 3

Ikeda isolated the compound from food sources and identified it as a basis for this type of taste

Answer 3

unani

Question 4

Fifth basic taste which means rich meaty or savory taste

Answer 4

umami

Question 5

Ikaeda founded this company which mass produced MSG and popularized its use

Answer 5

ajinomoto

Question 6

MSG was widely maligned in the US and was dubbed this

Answer 6

chinese restaurant syndrome

Question 7

Alleged symptoms of headache, flushing, and sweating associated with eating of MSG-laden cuisine in Chinese restaurant

Answer 7

chinese restaurant syndrome

Question 8

amino acid that is naturally abundant in meat products, mushrooms, cheeses, and fermented products

Answer 8

glutamate

Question 9

average person’s intake of glutamate

Answer 9

10-20g

Question 10

receptor where glutamate binds to give food the characteristic savory flavor

Answer 10

umami receptor

Question 11

Major excitatory neurotransmitter in the human brain that plays a key

Answer 11

umami receptor

Question 12

generally regarded as safe for use as seasoning, and its touted neurologic side effects has been debunked because dietary glutamate cannot cross the blood-brain barrier

Answer 12

MSG

Question 13

the real problem with MSG-laden snack foods

Answer 13

high salt content

Question 14

building blocks of protein

Answer 14

amino acids

Question 15

Three structural features in amino acids:

Answer 15

➢α-amino group
➢α-carboxylic acid
➢vaiable functional group

Question 16

form of amino acid where the H+ of the carboxylic acid was donated to the amine

Answer 16

zwitterionic form

Question 17

has an equal number positive and negative charges so its net charge is zero

Answer 17

zwitterionic form

Question 17

located to the left side, hence, the complete designation is L-α-amino acid

Answer 17

α-amino group

Question 18

all standard amino acid are therefore said to be _____handed

Answer 18

left handed

Question 19

the designation of left handedness of amino acid implies this nature of amino
acids which make them capable of rotating plane-polarized light in solution

Answer 19

chiral

Question 20

determines the identity of an amino acid

Answer 20

R-group, side chain

Question 21

nonpolar and neutral amino acids which includes (GAVLI):

Answer 21

aliphatic amino acid

Question 22

pertaining to nonaromatic hydrocarbon compounds in which the constituent carbon atoms can be straight-chain, branched chain, or cyclic, as in alicyclic compounds; saturated, as in the paraffins; or unsaturated, as in the olefins and alkynes

Answer 22

aliphatic

Question 23

example of aliphatic AA

Answer 23

Glycine
Alanine
Valine
Leucine
Isoleucine

Question 24

non-polar and neutral amino acid which has a secondary cyclic amine which is known as imine

Answer 24

secondary amine or imino acid

Question 25

example of secondary amine or imino acid

Answer 25

proline

Question 26

non-polar and neutral amino acids with bulky aromatic side chain which includes (FYW):

Answer 26

aromatic AA

Question 27

example of aromatic AA

Answer 27

tyrosine tryptophan phenylalanine

Question 28

polar and neutral amino acids with hydroxyl side chain which includes (ST):

Answer 28

alcoholic AA

Question 29

example of alcoholic AA

Answer 29

serine threonine

Question 30

slightly polar and neutral amino acids with sulfur-containing side chain which includes (CM

Answer 30

sulfur-containing AA

Question 31

example of sulfur containing AA

Answer 31

cysteine methionine

Question 32

polar and negatively charged amino acids with carboxylic acid side chain which includes

Answer 32

acidic AA

Question 33

acidic AA

Answer 33

glumatic acid aspartic actid

Question 34

polar and positively charged amino acids with amine side chain (KHR)

Answer 34

basic AA

Question 35

example of basic AA

Answer 35

Lysine Arginine Histidine

Question 36

means that they can behave both as an acid and base

Answer 36

amphoteric

Question 37

ionizable group that can accept or donate H+ at a particular pH

Answer 37

prototrophic

Question 38

value for the α-COOH group which is expected on the acidic pH range

Answer 38

pka1

Question 39

α-NH2 group which is expected on the basic pH range

Answer 39

pka2

Question 40

R group in which pH depends on the nature of amino acids

Answer 40

pka3

Question 41

most useful way of investigating the acid-base properties of amino acids and peptides

Answer 41

titration

Question 42

Involves the progressive neutralization of all prototrophic groups

Answer 42

titration

Question 43

titration profile of tryptophan

Answer 43

check answer in reviewer

Question 44

shows the change in pH of an amino acid in the process of titration

Answer 44

titration curve

Question 45

this value of the prototrophic group can be determined from the titration curve

Answer 45

pka

Question 46

point where there is sudden change in the slope of the curve

Answer 46

inflection points

Question 47

medial zones of two pKa values where pH change is the slowest

Answer 47

buffering region

Question 48

located within the buffering zone of an amino acid

Answer 48

pI

Question 49

its pI showed that it is an effective buffer at physiologic pH

Answer 49

histidine

Question 50

short amino chain of amino acids which are linked together by amide bond between the α -carboxylic group of one amino acid can react with the α-amino group of another

Answer 50

peptide

Question 51

amine bond that connects the two amino acids

Answer 51

peptide bond

Question 52

free amino group

Answer 52

n-terminal group

Question 53

free α-carboxylic acid * n to c terminal – peptides are always named in this order

Answer 53

c-terminal group

Question 54

suffix added to the n-terminal

Answer 54

-yl

Question 55

recommended to show the titration process of peptides

Answer 55

structural condensation

Question 56

useful way of analyzing the acid-base properties of amino acids and peptides

Answer 56

titration

Question 57

➢ Useful way of identifying an unknown amino acid based on its pKa values and pI

Answer 57

titration

Question 58

reveals which species predominates at particular pH

Answer 58

titrimetric profile

Question 59

recite procedure of amino acid titration

Answer 59

EXPERIMENT ON AMINO ACID TITRATION 1. Weigh 0.25g of unknown amino acid sample in a 250 ml beaker using toploading balance 2. Add 15ml of distilled water and stir to dissolve the sample 3. Using a syringe, add 0.200 M HCl while stirring until the pH of the solution drops to 1.50 4. Titrate with 0.20 ml increments of 0.200 M NaOH, stir then measure the pH after each increment and record the volume of NaOH and pH values 5. Continue the process until the pH of the solution reaches past 11 6. Using MS Excel, graph the pH against the volution of the added NaOH 7. Analyze the resulting titration curve and estimate the pka values from the inflection points of the curve 8. Determine the unknown amino acid based on the identified experimental pKa values, compare the experimental pka values with the theoretical values and calculate the percent error 9. Draw the titrimetric profile of the identified amino acid. Calculate the theoretical and experimental pI of the amino acid and determine percent error