Exam 1 AA digestion and analysis

Question 1

Aliphatic AA

Answer 1

Gly, ser, ala, thr, val, leu, ile

Question 2

Aromatic aa

Answer 2

Phe, tyr, trp

Question 3

Heterocyclic aa

Answer 3

Trp, pro, hypro

Question 4

Basic aa

Answer 4

Arg, Lys, his

Question 5

Sulfur aa

Answer 5

Cys, met

Question 6

Pepsin breaks cho end of

Answer 6

Aromatic and acidic aa (trp, tyr, phe, asp, glu)

Question 7

Trypsin breaks cho end of

Answer 7

Lys and arg

Question 8

Chymotrypsin breaks cho end of

Answer 8

Aromatic aa (phe, tyr, trp)

Question 9

Elastase breaks cho end of

Answer 9

Aliphatic aa (ser, ala, val, leu, ile, thr, gly)

Question 10

Carboxypeptidase A breaks end of chain cho end of

Answer 10

Aromatic aa(phe, tyr, trp)

Question 11

Carboxypeptidase B breaks end of chain cho end of

Answer 11

Basic aa (Lys, his, arg)

Question 12

Essential AA

Answer 12

HILLMA PheTrpThreVa CysTyr
+ gly and pro for chicken

Question 13

B transport system

Answer 13

Dipolar alpha aa, depends on Na gradient and requires energy

Question 14

B° + transport system

Answer 14

Dipolar alpha AA, basic aa and cys. Requires energy

Question 15

b ° + transport system

Answer 15

Dipolar alpha aa, basic and cys. Same as B° + but does not depend on Na gradient and does not require energy

Question 16

X- AG transport system

Answer 16

Acidic aa, depends on na gradient, also uses K and uses energy

Question 17

y+ transport system

Answer 17

Basic aa, does not depend on na gradient or other ions or energy

Question 18

IMINO transport system

Answer 18

IMINO acids, uses Na gradient, also Cl and uses energy

Question 19

Beta transport system

Answer 19

Beta aa, uses na gradient, Cl and energy

Question 20

What’s the N content in SBM protein?

Answer 20

18.5, using the 6.25 factors overestimates CP in it

Question 21

Key steps of Kjeldahl

Answer 21

Digest sample using concentrated sulfuric acid and heat,
Cu and K sulfates as catalysts,
forms ammonium sulfate
treated with 50% sodium hydroxide
ammonia is trapped in boric acid
then titrated with HCl

Question 22

Key steps of combustion method

Answer 22

Sample is introduced to pressurized tube and combusted with pure oxygen at min of 950 C
The products (NOx, N2, CO2, H2O and O2) are allowed to equilibrate
An aliquot is sampled and carried by He through a series of reagents to remove H2O, CO2 and excess O2
The N products that remain are converted to N2 when heated in the presence of N catalyst reagents
He is used to carry the isolated N2 through thermal conductivity detector that measures N

Question 23

how are samples on average hydrolyzed prior to AA analysis? and for free AA

Answer 23

with HCl at 110 C for 24 hours in vacuum, for analysis of free AA they must be ultrafiltrated

Question 24

What are the AA that cannot be digested in the conventional way for AA analysis?

Answer 24

Ile and Val require 48-72h
Sulfur AA Met and Cys are prone to partial oxidation so they must be treated before hydrolysis
Gln and Asn are converted to Glu and Asp, so must be converted to stable derivatives
Trp is completely destroyed and requires base hydrolysis (sodium hydroxide)

Question 25

what are the possible AA analysis methods?

Answer 25

gas chromatography (GC), high performance liquid chromatography (HPLC), Ion exchange chromatography (IEC), and capillary electrophoresis (CE)

Question 26

What are the main characteristics of GC analysis of AA?

Answer 26

AAs must be converted to their volatile derivatives such as HFB isobutyl and then separated in columns. It’s not much use in animal nutrition studies, and require complex derivatization and purification

Question 27

What are the main characteristics of HPLC analysis of AA?

Answer 27

Largest advances in AA analysis. AAs are reacted with reagents to form fluorescent or UV-absorbing derivatives that are separated in the column, derivatizing agent can be DABS-Cl, FMOC, PITC. due to errors results should be replicated and reported with error ranges

Question 28

What are the main characteristics of IEC analysis of AA?

Answer 28

AA are separated in a column, mixed with a derivatization agent, passed through a reaction coil and passed through a fluorometric or spectrophotometric detector.
Requires expensive instrumentation and columns, has complex mobile phases and has low sensitivity