Proteins Flashcards
Proteins characteristics
Polymers of 20 amino acids joined by peptide bonds synthesized in the ribosomes by reading mRNA information
Proteome
The pool of proteins, it is a functional expression of the genome, it varies with the cell type, developmental stage, and environmental conditions.
Amino acids structure
Bound to a central Alpha Carbon:
- Carboxylic acid group (HOOC)
- Amino group (NH2)
- H
- R lateral chains that varies for each amino acid and determine its chemical properties.
The five main classes of aa
- Nonpolar aliphatic (hydrophobic)
- Aromatic (generally nonpolar)
- Polar uncharged
- Negatively charged
- Positively charged
Polarity of R groups
Very variable, goes from totally nonpolar or hydrophobic (water-insoluble) to highly polar or hydrophilic (water-soluble).
Nonpolar aliphatic groups
- Glycine (allows flexibility)
- Alanin
- Proline (reduces flexibility)
- Valine
- Leucine
- Isoleucine (most hydrophobic)
- Methionine
Aromatic groups
- Phenylananine (non polar)
- Tryptophan (non polar)
- Tyrosine (polar)
Polar uncharged
- Serine
- Threonine
- Cysteine
- Asparaigne
- Glutamine
Negatively charged
- Aspartate
- Glutamate
Positively charged
- Lysine
- Arginine
- Histidine
Properties of amino acids
- Optical properties (enantiomers, dextrorotatory, levorotatory)
- Electric dipoles (soluble in water)
- Amphoteric compounds (change charge depending on the solution pH)
Amphoteric property of aminoacid
Amino acids form dipolar ions in aqueous medium (neutral pH)
Carboxyl group loses a proton and amino group accepts a proton.
A dipolar ion can act like an acid or like a base depending on the pH of the solution.
The amino acid behaves like a base it captures protons and the pH decreases.
The amino acid behaves like an acid it loses protons and the pH increases.
