INTRODUCTION TO BIOCHEMISTRY

ANDCARBOHYDRATES

BYDR. MARYJANE

Biochemistry is the study of the chemical processes and

transformations in living organisms

Biochemistry is the study of the structure and function of cellular components, such as proteins, carbohydrates, lipids, nucleic acids, and other biomolecules

AMINO ACIDS

BYDR. MARYJANE

INTRODUCTION

• There are about 300 amino acids that occur in nature but only 20 of them are found in proteins.

• Each amino acids has the following four groups or atoms attached to the alpha (α) carbon:

• 1. amino group (NH₂)• 2. carboxyl group (COOH)• 3. hydrogen atom (H)• 4. distinctive side chain or radical group (R)

STUCTURE OF AMINO ACIDS

Showing you how the R group varies

• All amino acids can either be:• 1. D- amino acids, i.e., the amino group is

attached to the right of the α-carbon. This is found in some antibiotics and bacteria cell walls• 2. L-amino acid, i.e., the amino group is

attached to the left of the α-carbon. This is found in proteins.• These two forms are called stereoisomers

or enantiomers

Classification according to charge and polarity Amino acids with Nonpolar side chains or

R-groups Amino acids with Polar side chains: a. uncharged polar side chains b. acidic side chains c. basic side chains

Nonpolar side chains

CLASSIFICATION OF AMINO ACIDS• A. Amino acids with nonpolar side R- Groups.• Glycine (Gly)• Alanine (Ala)• Valine (Val)• Leucine(Leu)• Isoleucine (Ile)• Phenylalanine (Phe)• Tryptophan (Trp)• Methionine (Met)• Proline (Pro)

• Proline differs from the other amino acids in that it the α-amino N form a rigid, five membered ring structure and also contains a secondary amino group rather than a primary amino group. Therefore it is frequently referred to as an imino acid

Imino acid proline

AMINO ACIDS WITH POLAR R-GROUPS

• Amino acids with uncharged polar R-Groups:• Serine• Threonine• Tyrosine• Asparagine• Glutamine• cysteine

Disulfide bond• The side chain of cysteine

contains a sulfhydryl group (-SH). The –SH group of two cysteines can become oxidized to form cystine which contains a covalent cross link called disulfide bond (-S-S-).

• C. Amino acids with acidic R- Groups: are proton donors & negatively charged at physiologic pH

• Aspartic acid (Asp) • Glutamic acid (Glu)

• D. amino acids with basic R- Groups: are proton acceptors & positively charged at physiologic pH

• Histidine (His)• Lysine (Lys)• Arginine (Arg)• Histidine and arginine are needed in growing

children

CLASSIFICATION ACCORDING TO THE AMINO ACID STRUCTURE.

• Can either be aromatic or aliphatic• A. aromatic amino acids• B. aliphatic amino acids

Aromatic amino acids

Phenylalanine: contains a benzene ring Tyrosine: contains a phenol group Tryptophan: contains a heterocyclic

structure, indole

Amino Acids Abbreviations

Nutritional classification of amino acids Essential amino acids Non essential amino acids

Essential amino acids

Arginine Histidine Isoleucine Leucine Threonine Lysine Methionine Phenyalanine Tryptophan Valine Histidine and arginine are essential only for

periods when cell growth exceeds production such as during childhood

Non essential amino acids

Tyrosine Glycine Alanine Cysteine Serine Aspartate Asparagine Glutamate Gutamine proline

METABOLIC CLASSIFICATION• Are classified according to their metabolic fate in the body

into

• Glucogenic amino acid• Ketogenic amino acid• Both glucogenic and ketogenic amino

acid

• ketogenic amino acids: these gives ketone bodies. Leucine and Lysine are the only ketogenic amino acid.

• glucogenic and ketogenic amino acids: these gives both ketone bodies and glucose. They are: phenylalanine, tyrosine, tryptophan and isoleucine.

• glucogenic amino acids: it gives glucose. They include the rest of amino acids not included in the 1st and 2nd groups, they are: alanine, valine, proline, methionine, glycine, serine, threonine, cysteine, asparagine, glutamine, aspartate, glutamic acid, arginine and histidine.

FUNCTIONS OF AMINO ACIDS.• A. structural functions: these are amino acids found in the

structure of:• 1. body peptides and proteins: e.g., plasma proteins, tissue

proteins, enzymes etc.• 2. hormones; some hormones are amino acid derivatives

e.g., thyroxine and catecholamines.• 3. amines; some amino acids give corresponding amines by

decarboxylation e.g. histidine gives histamine.• B. Neurotransmitters: some amino acids, glutamate acts as

neurotransmitters.• C. Detoxification: some amino acids are used in

detoxification reactions e.g., glycine• D. Health and growth: essential amino acids support growth

in infants and maintain health in adults.

TyrosineTyrosine is involved in the synthesis of:

DopamineCatecholamines-Epinephrine,nor epinephrine,dopamineChemical messengers-Transmit impulses across the neurons in the brain and onward to the musclesControl muscle movement

TyrosineNor Epinephrine

TyrosineMelaninTyrosinase-Deficiency-Albinism

Phenylalanine

Epinephrine

Phenylalanine

TryptophanTryptophan is involved in the synthesis of:

Melatonin

Serotonin

Niacin