Lesson today

Protein

Teacher : IsroliLaboratory : Animal Physiology and Biochemistry

Faculty : Animal AgricultureDiponegoro University

Biological Functions of Proteins

• Principal organic chemical constituents of body organs and soft tissues

• Enormous functional diversity– Cell membrane structure and function– Enzymes– Hormones and other chemical messengers– Immune factors (antibodies)– Fluid balance– Acid-base balance– Transport– Source of energy and glucose

The Structure of Amino Acids

H2NC

CO2H

R

H

NH2 amino group, COOH carboxyl group, R – side chain group can be a series of functional groups

Amino Acids

• The monomer unit of proteins

C CH

NH2

R

HO

O

•R is the side chain.•One of 20 different chemical compounds•Some R-groups are acid (other alkali)•Some R-groups are water soluble (others are not)

Chiral carbon (L-series)

Classification of Amino Acids

• Classification– Structure– Net charge– Polarity– Essentiality

• Neutral– Aliphatic– Aromatic– Sulfur

• Acidic

• Basic

• Heterocyclic

Aliphatic (opened)

Aromatic

Sulfur

Acidic

Basic

Heterocyclic

Essentiality

• Essential– Amino acids not synthesize in sufficient

amounts in the animal body– Required in the diet

• Nonessential– Adequately synthesized in the tissue

• No specific requirement

• Vary by species

Essential Amino Acids

• Arginine

• Histidine

• Isoleucine

• Leucine

• Lysine

• Methionine

• Phenylalanine

• Threonine

• Tryptophan

• Valine

• Proline

• Taurine

Abbreviations and Codes

Alanine A, Ala

Arginine R, Arg

Asparagine N, Asn

Aspartic acid D, Asp

Cysteine C, Cys

Glutamine Q, Gln

Glutamic Acid E, Glu

Glycine G, Gly

Histidine H, His

Isoleucine I, Ile

Leucine L, Leu

Lysine K, Lys

Methionine M, Met

Phenylalanine F, Phe

Proline P, Pro

Serine S, Ser

Threonine T, Thr

Tryptophan W, Trp

Tyrosine Y, Tyr

Valine V, Val

Leu L

-C-C-CONH2-C-CONH2

-C-COOH -C-C-COOH

-H -CH3

-C-OH -C-SH

-C-C-S-C PPro

-C-C C N N+

-C-C-C-C-NH3+ -C-

-C- -OH

-C-N

South lineCircular line

Central line

Nan-Kan line

Chung-San lineNorthwest line

Aliphatic

Amide

Acidic

Imino,Circular

Basic

SulfurHydroxy

Aromatic-C-C-C-N-C-N

N+

=

C-C-C-C

C-C-C-C

C C-C

C C C HN C-COOH

-C-C OH

Gln QAsn N

Asp D Glu EPhe F

Arg R

Lys K

His H

Gly G AAAla VVal I Ile

YTyr

Ser S

Thr T Met M

Cys C

Amino Acid Subway MapTrp W

Non-polar

Polar

Jua

ng

RH

(2

00

4)

BC

ba

sics

This is NOT a metabolic pathway

PO

LAR

NO

N-

PO

LAR

Tyr His

Gly

Acidic Neutral Basic

Asp

Glu GlnCys

Asn Ser

Thr Lys

Arg

Ala

ValIle

Leu MetPhe Trp

Pro

Classification of Amino Acids by Polarity

Polar (hydrophilic) or non-polar (hydrophobic), it is the bases of the amino acid properties.

Juang RH (2003) Biochemistry

The 20 Amino Acids Structure

TUGASTulis structur 20 asam amino

berdasarkan klasifikasi berikut ini1. A.a. rantai samping alifatik

a) glisinb) alaninc) valin

2. A.a. rantai samping hidroksila) serinb) treonin

3. A.a. rantai samping beleranga) sisteinb) metionin

4. A.a. rantai samping karboksila) aspartic acidb) asparaginc) glutamic acidd) glutamin

5. A.a. rantai samping basa a) argininb) histidinc) lisind) hidroksilisin

6. A.a. rantai samping cincin aromatik

a) tirosin

b) fenil alanin

c) tritofan

7. Asam imino

a) prolin

b) hidroksiprolin

Protein

Amino Acid (AA)-Protein

Peptides (from the Greek πεπτος, "digestible"), are formed through condensation of amino acids through peptide bonds.

Amino acids: basic unit

Peptides: amino acid chain, containing 2 or more AA.

Polypeptides: containing less than 50 AA.

Protein: > 50 AA.

The Peptide Bond

• A peptide bond is an amide bond between the carboxyl group of one amino acid and the amino group of the next amino acid

O CH3 O

+ || + | ||H3N—CH2—C—O– + H3N—CH—C—O–

O H CH3 O + || | | ||

H3N—CH2—C—N—CH—C—O– + H2O peptide bond

Peptide Bonds

C CH

NH2

R

HO

O

C CH

NH2

R

HO

O

C CH

NH

R

HO

OC C

HNH2

R

O

Water

Amino acids

Peptide bond formation:

Disulfide Bonds

• Two cysteine molecules under oxidizing conditions

• Intermolecular or intramolecular cross-link

CH2

SH CH2

SH

CH2

SSCH2

[O]

Protein Structures

ProGly Leu Ser

Proteins consist of a long chain ofamino acids, the primary structure

N

O H

RH

N

O H

R H

N

O H

RH

N

O H

R H

N

OH

R H

N

OH

R H

N

OH

R H

N

OH

R H

Side chain

H-bond

Backbone

Amino acid