what are proteins? amino acids

Proteins & Enzymes October 15 & 16, 2012

What are Proteins?Amino Acids


Functions• Enzymes• Hormones• Defense• Structure• Transport


Classification of Proteins (Chemical Composition)Simple Proteins – consist of ONLY Amino Acids

Conjugated Proteins - have NON-Protein Portions as major component

• Glycoproteins• Lipoproteins• Phosphoproteins


Classification of Proteins (Shape)Globular Proteins – tightly folded, Water Soluble• Involved in: synthesizing, transporting, and

metabolizing• Such as: Hemoglobin, Hormones, Antibodies,

Enzymes

Fibrous Proteins – long, Water Insoluble• Involved in: Structural material of cells and tissues• Such as: Keratin, Elastin, Collagen


Globular Proteins

Fibrous Proteins


Protein StructurePrimary (1o) Structure• Peptide Sequence

• Amino Acids in Peptide Chain called, “Amino Acyl Residues”

• Peptide bonds form between Carbonyl Carbon & Amino Nitrogen, by removal of an O- from the Carbonyl and 2 H+ from the Nitrogen… Removal of H2O forms Peptide Bonds


Secondary (2o) Structure• Folding of Peptide Sequence (1o

Structure)• Hydrogen Bonding utilizing Peptide-

Bonding Atoms• Intra-chain Hydrogen Bonding (α Helix)• Hair, Wool, Horns, and Feathers

• Inter-chain Hydrogen Bonding (β Pleated Sheets)• Silk


Tertiary (3o) Structure• Folding and Twisting of 2o Structure

• Hydrophobic R groups cluster on inside of protein away from water

• Hydrophilic R groups cluster on outside of protein near water

• Hydrogen Bonding of non-peptide bonding atoms• Ionic Salt-bridges, COO-

● ● ● ● +NH3

• Disulfide Bonds (Disulfide Bridges) b/n SH-Groups• Cysteine not Methionine


Quaternary (4o) Structure• Folding, Twisting, and Other Interactions b/n

different polypeptide strands in pre-existing 3o structure• Hydrophobic Bonding and Interactions• Hydrogen Bonding of Non-peptide Bonding Atoms• Ionic Salt-bridges, COO-

● ● ● ● +NH3

• Disulfide Bonds (Disulfide Bridges) b/n SH-Groups• Classifications: Dimers, Trimers, Tetramers, Pentamers,

Hexamers• EX: Hemoglobin – tetramer (2 α subunits & 2 β subunits)

• Each unit contains the Heme prosthetic group which contains Iron and is responsible for binding O2 in Blood.


Enzymes

what are proteins? amino acids

Documents

enzymesproteins enzymesoctober

enzymes fibrous proteins

o structurehydrophobic

peptide chain

nonprotein portions

protein structureprimary

carbonyl carbon amino

water insolubleinvolved