matriculation chemistry ( amino acids ) part 1
TRANSCRIPT
-
8/14/2019 Matriculation Chemistry ( Amino Acids ) part 1
1/24
Chapter 20 : Amino Acids and Proteins
Amino acidAmino acid: a compound that containsboth an amino group, -NH2 and acarboxyl group, -COOH
-amino acid:-amino acid: an amino acid in which
the amino group is on the carbonadjacent to the carboxyl group
CH3CH2 C COOH
H
NH2
-amino acid
20 amino acids
Naming
Zwitterion
Isoelectric point
Structures in:
Acidic
Basic
pI
20.1
20.1 : Introduction 20.2 : Chemical Properties
NH2 C COOH
H
CH2CH3
-
8/14/2019 Matriculation Chemistry ( Amino Acids ) part 1
2/24
Chapter 20 : Amino Acids and Proteins
Name Structure
Glycine
Gly
AlanineAla
ValineVal
H CH
NH2
COOH
H3C CH
NH2
COOH
HC CH
NH2
COOH
CH3
CH3
-amino acid
20 amino acids
Naming
Zwitterion
Isoelectric point
Structures in:
Acidic
Basic
pI
20.1
20.1 : Introduction 20.2 : Chemical Properties
-
8/14/2019 Matriculation Chemistry ( Amino Acids ) part 1
3/24
Chapter 20 : Amino Acids and Proteins
Name Structure
Leucine
Leu
IsoleucineIle
PhenylalaninePhe
CHCH2
CH3
CH3
CH
NH2
COOH
CH
NH2
COOHCH3CH2CH
CH3
CH2 CH
NH2
COOH
-amino acid
20 amino acids
Naming
Zwitterion
Isoelectric point
Structures in:
Acidic
Basic
pI
20.1
20.1 : Introduction 20.2 : Chemical Properties
-
8/14/2019 Matriculation Chemistry ( Amino Acids ) part 1
4/24
Chapter 20 : Amino Acids and Proteins
Name Structure
Threonine
Thr
CysteineCys
MethionineMet
CH2 CH2
CH2NH
C
COOH
H
HO CH2 CH
NH2
COO
H
CH3 C
H
OH
CH
NH2
COOH
-amino acid
20 amino acids
Naming
Zwitterion
Isoelectric point
Structures in:
Acidic
Basic
pI
20.1
20.1 : Introduction 20.2 : Chemical Properties
-
8/14/2019 Matriculation Chemistry ( Amino Acids ) part 1
5/24
Chapter 20 : Amino Acids and Proteins
Name Structure
Tryptophan
Trp
ProlinePro
SerineSer
CH2 CH2
CH2NH
C
COOH
H
HO CH2 CH
NH2
COOH
O
NH2NH
OH
-amino acid
20 amino acids
Naming
Zwitterion
Isoelectric point
Structures in:
Acidic
Basic
pI
20.1
20.1 : Introduction 20.2 : Chemical Properties
-
8/14/2019 Matriculation Chemistry ( Amino Acids ) part 1
6/24
Chapter 20 : Amino Acids and Proteins
Name StructureThreonineThr
CysteineCys
MethionineMet
CH3 C
H
OH
CH
NH2
COOH
HS CH
NH2
COOHCH2
CH
NH2
COOHCH3 S CH2CH2
-amino acid
20 amino acids
Naming
Zwitterion
Isoelectric point
Structures in:
Acidic
Basic
pI
20.1
20.1 : Introduction 20.2 : Chemical Properties
-
8/14/2019 Matriculation Chemistry ( Amino Acids ) part 1
7/24
Chapter 20 : Amino Acids and Proteins
Name Structure
Tyrosine
Tyr
AsparagineAsn
GlutamineGln
NH2CCH2CH COOH
O NH2
NH2CCH2CH2CHCOOH O NH2
CH
NH2
COOHCH2HO
-amino acid
20 amino acids
Naming
Zwitterion
Isoelectric point
Structures in:
Acidic
Basic
pI
20.1
20.1 : Introduction 20.2 : Chemical Properties
-
8/14/2019 Matriculation Chemistry ( Amino Acids ) part 1
8/24
Chapter 20 : Amino Acids and Proteins
Name StructureAsparticacid
Asp
Glutamicacid
GluLysineLys
HOOCCH2CH2CHCOOH
NH2
HOOCCH2CHCOOH
NH2
H2NCH2CH2CH2CH2CH COOH
NH2
-amino acid
20 amino acids
Naming
Zwitterion
Isoelectric point
Structures in:
Acidic
Basic
pI
20.1
20.1 : Introduction 20.2 : Chemical Properties
-
8/14/2019 Matriculation Chemistry ( Amino Acids ) part 1
9/24
Chapter 20 : Amino Acids and Proteins
Name StructureArginineArg
HistidineHis
H2NCNH(CH2)3CHCOOH
NH NH2
HCC=CH2CH COOH N NH NH2
CH
-amino acid
20 amino acids
Naming
Zwitterion
Isoelectric point
Structures in:
Acidic
Basic
pI
20.1
20.1 : Introduction 20.2 : Chemical Properties
-
8/14/2019 Matriculation Chemistry ( Amino Acids ) part 1
10/24
Chapter 20 : Amino Acids and Proteins
H C COOH
H
NH2
i)
ethanoic acid2 1
2-amino
H C COOH
CH3
NH2
ii)
2 1
3
propanoic acid2-amino
H C COOH
CH2OH
NH2
iii)
2 1
3
propanoic acid
2-amino-3-hydroxy
IUPAC Name
-amino acid
20 amino acids
Naming
Zwitterion
Isoelectric point
Structures in:
Acidic
Basic
pI
20.1
20.1 : Introduction 20.2 : Chemical Properties
-
8/14/2019 Matriculation Chemistry ( Amino Acids ) part 1
11/24
Chapter 20 : Amino Acids and Proteins
pentanoic acid2,5-diamino
hexanedioic acid2-amino
2 1
3 4 5
H C COOH
CH2CH
2CH
2COOH
NH2
v)
H C COOH
CH2CH2CH2NH2
NH2
iv)
2 1
3 4 5 6
IUPAC Name
-amino acid
20 amino acids
Naming
Zwitterion
Isoelectric point
Structures in:
Acidic
Basic
pI
20.1
20.1 : Introduction 20.2 : Chemical Properties
-
8/14/2019 Matriculation Chemistry ( Amino Acids ) part 1
12/24
Chapter 20 : Amino Acids and Proteins
Amino acids can undergo aninternal acid-base reaction, in which aproton is transferred from thecarboxyl (-COOH) to the amino group(-NH2) to form dipolar ion calledzwitterion.
H C COOH
CH2CH2CH3
NH2
(neutral)
H C COO
CH2CH
2CH
3
NH3
-
+
(dipolar ion @zwitterion)
-amino acid
20 amino acids
Naming
Zwitterion
Isoelectric point
Structures in:
Acidic
Basic
pI
20.1
20.1 : Introduction 20.2 : Chemical Properties
Zwitterion
-
8/14/2019 Matriculation Chemistry ( Amino Acids ) part 1
13/24
Chapter 20 : Amino Acids and Proteins
In general, zwitterion is electricallyneutral and exists at specific pH
Isoelectric Point (pI)
This particular pH is called isoelectricpoints
Each amino acid has its specific pIExample:
Amino Acid Structure pI
Glycine(Gly)
6.1H CH
NH2
COOH
Lysine
(Lys)
9.7
Asparticacid(Asp)
2.9HOOCCH2CHCOOH
NH
2
H2N(CH2)4CH COOHNH2
-amino acid
20 amino acids
Naming
Zwitterion
Isoelectric point
Structures in:
Acidic
Basic
pI
20.1
20.1 : Introduction 20.2 : Chemical Properties
-
8/14/2019 Matriculation Chemistry ( Amino Acids ) part 1
14/24
Chapter 20 : Amino Acids and Proteins
InAcidic
The cation, H3N+ CH2 COOHpredominates (Amino acids as base)
InBasic
The anion, H2N CH2 COO-
predominates (Amino acids as acid)InpI
The zwitterion, H3N+CH2COO-predominates (Amino acids as
amphoteric)Gly (pI = 6.1)
at pH = 6.1
NH2CH2COOH
-+NH3CH2COO
-NH2CH2COO
at pH < 6.1 at pH > 6.1
+NH3CH2COOH
-amino acid
20 amino acids
Naming
Zwitterion
Isoelectric point
Structures in:
Acidic
Basic
pI
20.1
20.1 : Introduction 20.2 : Chemical Properties
-
8/14/2019 Matriculation Chemistry ( Amino Acids ) part 1
15/24
Chapter 20 : Amino Acids and Proteins
a) Reaction with HCl
R C NH2
COOH
R'
+ HCl R C NH3Cl
COOH
R'_+
Example:
20.2 : Chemical Properties
Reactions ofNH2 group:
Peptide bond
HCl
NaOH
HNO2
ROH
Reactions of-COOH group:
20.2
H C NH2COOH
CH2CH3
+ HCl
20.1 : Introduction
H C NH3ClCOOH
CH2CH3_+
Importance
-
8/14/2019 Matriculation Chemistry ( Amino Acids ) part 1
16/24
Chapter 20 : Amino Acids and Proteins
b) With Nitrous Acid (HNO2)
20.2 : Chemical Properties
Reactions ofNH2 group:
Peptide bond
HCl
NaOH
HNO2
ROH
Reactions of-COOH group:
20.2
20.1 : Introduction
elimination of N2(g)
R C
COOH
R'
+
carbocationH2O
2-hydroxy
carboxylic acid
Cl-
+
halocarboxylic
acid
- H+
Alkenoic
acid
Observation: Bubblingof gas (N2)
Importance
R C NH2
COOH
R'
R C N N
COOH
R'+
diazonium ion
NaNO2 / HCl
-5 to 0 oC
-
8/14/2019 Matriculation Chemistry ( Amino Acids ) part 1
17/24
Chapter 20 : Amino Acids and Proteins
Example:H C NH2
COOH
CH3
H C N N
COOH
CH3+
diazonium ion
NaNO2 / HCl
elimination of N2(g)
H C
COOH
CH3+
carbocation
H2O
H C OH
COOH
CH3Cl-+
H C Cl
COOH
CH3
- H+
H C
COOH
CH2
-
8/14/2019 Matriculation Chemistry ( Amino Acids ) part 1
18/24
Chapter 20 : Amino Acids and Proteins
c) Reaction with NaOH
Example:
20.2 : Chemical Properties
Reactions ofNH2 group:
Peptide bond
HCl
NaOH
HNO2
ROH
Reactions of-COOH group:
20.2
20.1 : Introduction
R C NH2
COOH
R'
+ NaOH R C NH2
COO Na
R'
_ +
H C NH2
COOH
CH2CH3
+ NaOH H C NH2
COO Na
CH2CH3
_+
Importance
-
8/14/2019 Matriculation Chemistry ( Amino Acids ) part 1
19/24
Chapter 20 : Amino Acids and Proteins
d) Reaction with ROH + HCl (catalyst)
Example:
20.2 : Chemical Properties
Reactions ofNH2 group:
Peptide bond
HCl
NaOH
HNO2
ROH
Reactions of-COOH group:
20.2
20.1 : Introduction
R C NH2
COOH
R'
+ R''OH + H2OR C NH2
COOR''
R'
H C NH2
COOH
CH2CH3
+ CH3OH
HCl
+ H2OR C NH2
COOR''
R'
Importance
-
8/14/2019 Matriculation Chemistry ( Amino Acids ) part 1
20/24
Chapter 20 : Amino Acids and Proteins
Peptidesareamino acid polymersin which the individual amino acidunits, are linked together by amidebonds, orpeptide bonds
Peptide Bond2amino acids react together, H2Ois eliminated.This is condensation reaction.
20.2 : Chemical Properties
Reactions ofNH2 group:
Peptide bond
HCl
NaOH
HNO2
ROH
Reactions of-COOH group:
20.2
2 amino acids form dipeptide3 amino acids form tripeptide15 30amino acids form oligopeptide> 30amino acids form polypeptide
20.1 : Introduction
Importance
-
8/14/2019 Matriculation Chemistry ( Amino Acids ) part 1
21/24
Chapter 20 : Amino Acids and Proteins
Formation of dipeptide bond:
+
+
H2O
H2N CH2 C OH H N C COOH
H CH3
H
H2N CH2 C N C COOH
H CH3
H
O
O
amide bond /
peptide bond
A dipeptide
Notes:
N-terminal (with free NH2) is
always written on the left and C-terminal (with free COOH) at theright side
20.1 : Introduction 20.2 : Chemical Properties
Reactions ofNH2 group:
Peptide bond
HCl
NaOH
HNO2
ROH
Reactions of-COOH group:
20.2
Importance
-
8/14/2019 Matriculation Chemistry ( Amino Acids ) part 1
22/24
Chapter 20 : Amino Acids and Proteins
Formation of tripeptide bond:
Write the structural formula of tripeptide with the followingsequence Gly-Ala-Tyr :
H2N CH2 C OH H N C COOH
H CH3
HOH N C COOH
H H
CH2 OH
Gly Ala Tyr
H2N CH2 C N C C
H CH3
HO
N C COOH
H
CH2 OHO
H
A tripeptide
-
8/14/2019 Matriculation Chemistry ( Amino Acids ) part 1
23/24
Chapter 20 : Amino Acids and Proteins
Importance of amino acids :
20.1 : Introduction 20.2 : Chemical Properties
Reactions ofNH2 group:
Peptide bond
Importance
HCl
NaOH
HNO2
ROH
Reactions of-COOH group:
20.2 Human beings can synthesize about half
of the amino acids needed to makeproteins.
Other amino acids, called the essentialessentialamino acidsamino acids, must be provided in the diet.
The ten essential amino acids are :
arginine (Arg) valine (val) methionine (Met)threonine (Thr) leucine (Leu) phenylalanine (Phe)histidine (His) isoleucine (Ile) lysine (Lys)trypthophan (Trp)
-
8/14/2019 Matriculation Chemistry ( Amino Acids ) part 1
24/24
Chapter 20 : Amino Acids and Proteins
Importance of proteins :
20.1 : Introduction 20.2 : Chemical Properties
Reactions ofNH2 group:
Peptide bond
HCl
NaOH
HNO2
ROH
Reactions of-COOH group:
20.2 Proteins are the most abundant organic
molecules in animals, playing importantroles in all aspects of cell structure and
function. Examples of protein functions :
Class of protein Examples Functions
structural protein collagen, keratin tendons, skin
hair, nails
enzymes DNA polymerase repair DNA
transport protein hemoglobin transport O2Importance