PROTEINS
Functions Amino Acids
• Enzymes They are the monomers of proteins
• Hormones (insulin and glucagon)
Each amino acid has a central carbon atom which is
• Haemoglobin and myoglobin
bonded to an amine group (NH2), a carboxylic acid
• Antibodies
group (COOH), and a hydrogen atom
• Collagen (found in animal tissues such as
bones, and artery walls)
• Keratin (hair, nails, skin)
• Muscle contraction (actin and myosin)
• Storage (casein in milk, ovalbumin in egg
white)
• Cell membrane components (receptor and
signaling proteins)
THE PEPTIDE BOND
C-N link between 2 amino acid molecules, formed by a condensation reaction
Mechanism:
• 1 amino acid loses a hydroxyl (-OH) group from its carboxylic acid group and the other loses a hydrogen atom
from its amine group
• The carbon of the first amino acid binds with the nitrogen of the second amino acid
• 2 amino acids joined together forms a dipeptide
• Polypeptide: A long chain of amino acids formed by condensation reactions between the individual amino acids
, PRIMARY STRUCTURE TERTIARY STRUCTURE
The sequence of amino acids in a polypeptide or The compact structure of a protein molecule resultin
protein from the 3 dimensional coiling of the already folded
Amino acids are covalently linked by peptide bonds chain of amino acids
TYPES OF BONDS:
Hydrogen bonds
• Formed between strongly polar groups
• Eg: -NH-, -CO-, -OH-
Disulfide bonds
SECONDARY STRUCTURE • Formed between cysteine molecules
• Strong covalent bonds
The structure of a protein molecule resulting from the • They can be broken by reducing agents
regular coiling or folding of the chain of amino acids Ionic bonds
• Formed between ionized amine groups and
Eg: Alpha helix and beta pleated sheet
ionized carboxylic acid groups
• Can be broken by pH changes
Weak hydrophobic interactions
• Formed between non polar R groups
QUATERNARY STRUCTURE
Contains hydrogen Contains hydrogen bonds
The 3 dimensional arrangement of 2 or more
bonds between the
oxygen of the -CO- polypeptides, or of a polypeptide and a non-protein
group of one amino
acid and the hydrogen component such as haem, in a protein molecule
of the -NH- group of
Made up of 2 or more polypeptide chains
the amino acid 4
places ahead of it Eg: Haemoglobin
• Hydrogen bonds are easily broken by high
temperatures and changes in pH
Functions Amino Acids
• Enzymes They are the monomers of proteins
• Hormones (insulin and glucagon)
Each amino acid has a central carbon atom which is
• Haemoglobin and myoglobin
bonded to an amine group (NH2), a carboxylic acid
• Antibodies
group (COOH), and a hydrogen atom
• Collagen (found in animal tissues such as
bones, and artery walls)
• Keratin (hair, nails, skin)
• Muscle contraction (actin and myosin)
• Storage (casein in milk, ovalbumin in egg
white)
• Cell membrane components (receptor and
signaling proteins)
THE PEPTIDE BOND
C-N link between 2 amino acid molecules, formed by a condensation reaction
Mechanism:
• 1 amino acid loses a hydroxyl (-OH) group from its carboxylic acid group and the other loses a hydrogen atom
from its amine group
• The carbon of the first amino acid binds with the nitrogen of the second amino acid
• 2 amino acids joined together forms a dipeptide
• Polypeptide: A long chain of amino acids formed by condensation reactions between the individual amino acids
, PRIMARY STRUCTURE TERTIARY STRUCTURE
The sequence of amino acids in a polypeptide or The compact structure of a protein molecule resultin
protein from the 3 dimensional coiling of the already folded
Amino acids are covalently linked by peptide bonds chain of amino acids
TYPES OF BONDS:
Hydrogen bonds
• Formed between strongly polar groups
• Eg: -NH-, -CO-, -OH-
Disulfide bonds
SECONDARY STRUCTURE • Formed between cysteine molecules
• Strong covalent bonds
The structure of a protein molecule resulting from the • They can be broken by reducing agents
regular coiling or folding of the chain of amino acids Ionic bonds
• Formed between ionized amine groups and
Eg: Alpha helix and beta pleated sheet
ionized carboxylic acid groups
• Can be broken by pH changes
Weak hydrophobic interactions
• Formed between non polar R groups
QUATERNARY STRUCTURE
Contains hydrogen Contains hydrogen bonds
The 3 dimensional arrangement of 2 or more
bonds between the
oxygen of the -CO- polypeptides, or of a polypeptide and a non-protein
group of one amino
acid and the hydrogen component such as haem, in a protein molecule
of the -NH- group of
Made up of 2 or more polypeptide chains
the amino acid 4
places ahead of it Eg: Haemoglobin
• Hydrogen bonds are easily broken by high
temperatures and changes in pH
