UNIT 8THE AMINO ACIDS

LEARNING OBJECTIVES

State the composition and describe the structure of amino acids.

Classify amino acids.List essential, semi-essential and non-

essential amino acids.2

AMINO ACID

Principal source: hydrolysis of protein

Proteins: high molecular weight substances (found in all living tissues)

attached to the same α-carbon

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R

AMINO ACID STRUCTURE

R

OH

C+H3N O

BUILDING AN R GROUP

CH3 CH2H CH2

OH

Glycine Alanine Phenylalanine Tyrosine

• With an H, glycine is the simplest amino acid• Alanine with a methyl group is the next simplest.• Phenylalanine arises when a phenyl group replaces an H on alanine’s

methyl group• Tyrosine evolves by adding an –OH group to the para position on the

phenyl ring of phenylalanine

Substances (found in all living tissues)

Upon Acid, base or enzymes catalyzed hydrolysis: Broken into thousands of amino acids molecules Most proteins produce approximately 20 different α-

amino acids Amino Acids - have both an amino & a carboxylic acid

group attached to the same α-carbon

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FUNCTIONS OF AMINO ACIDS

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FUNCTIONS OF AMINO ACIDS

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LEARNING OBJECTIVES

State the composition and describe the structure of amino acids.

Classify amino acids.List essential, semi-essential and non-

essential amino acids.

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Classification and Structure of Amino Acids

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•Aromatic

•Heterocyclic

•Sulphur containing amino acids

•Alipathic

LEARNING OBJECTIVES

State the composition and describe the structure of amino acids.

Classify amino acids.List essential, semi-essential

and non-essential amino acids.

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ESSENTIAL AMINO ACIDS

8 Amino Acids not Synthesized by the body & Therefore Must Be Taken in the Diet

1. Leucine

2. Isoleucine

3. Threonine

4. Tryptophan

5. Phenylalanine

6. Valine

7. Metheonine

8. Lysine

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MnemonicPvt. Tim Hall563 427 18

H – HistidineA – Arginine

ESSENTIAL AMINO ACIDS

Leucine

Isoleucine

Threonine

Tryptophan

Phenylalanine

Valine

Metheonine

Lysine

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To Maintain The Proper Nitrogen

Balance In The Body

CHILD: Growth failure

ADULT: decrease plasma protein and hemoglobin

levels

DEFICIENCY(1 or more)

SEMI-ESSENTIAL AMINO ACIDS

Histidine

Arginine

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Synthesized partially by the bodyBut not at the rate to meet the requirement in growing children, pregnant and lactating women

NON-ESSENTIAL AMINO ACIDS

Alanine

Aspartic acid

Serine

Proline

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•Can be synthesized by the body

•May not be required in the diet

•Derived from carbon skeletons of lipids and carbohydrates during metabolism or from the transamination of essential amino acids

•Complete or Adequate ProteinsComplete or Adequate Proteins:

Animal Proteins- Supply all of the essential amino acids.•Incomplete Proteins:

Vegetable Proteins- Low in one or more of the essential amino acids

ANIMAL PROTEINSANIMAL PROTEINS

SOURCE TYPE OF CHON

MISSING AA

Egg Complete None

Milk (Dairy) Complete None

Meat, Fish Complete None

SOURCE TYPE OF CHON MISSING AA

Wheat Incomplete Lysine

Corn Incomplete Lysine &Tryptophan

Rice Incomplete Lysine

Beans Incomplete Methionine &Tryptophan

Peas Incomplete Methionine

VEGETABLE PROTEINSVEGETABLE PROTEINS

•The two vegetable proteins are called complementary proteins.

–Ex. Rice and Beans

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

Central 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

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

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