Proteins – polypeptides compose of > 50 amino acids
- Enzymes or subunits of enzymes-enhancing the rates of reactions
- Structural or Mechanical roles
- Immune response roles
- Storage and transport of substances
- Source of amino acids for organisms that cannot synthesize amino acids naturally
- Column chromatography
- Density gradient centrifugation
- enzymatic digestion
- Fibrous –not water soluble: Collagen
- Globular- mostly water soluble : Globulin, Hemoglobin and Albumin-Globular A.
Optimum temperature at which the catalyze rate is at its greatest is 60 o and with optimum pH of 4. 5 – Sucrose -> Invertase-> glucose + fructose B. Casein- globular proteins; tend to fold back on themselves into compact, nearly spherical units, relatively hydrophobic but easily solubilized in to as colloidal suspension. with numerous of pro-residues that do not interact, no disulfide bridges -relatively little 3o structure -phosphoprotein(PO43-) attached to OH- groups of some amino acid R-groups acts as food source and supplies amino acids and inorganic elements CA and P. -pI – 4. 6 pH ;
insoluble at less than 4. 6 -pH= 6. 6 – casein has (-) charge in milk and is solubilized at salt, exists in milk as Calcium caseinate -if acid is added, (-) charges on the outer surface micelles are neutralized by protonation at the phosphate groups and the neutral protein precipitates with the Ca 2+ ion remains in solution casein is precipitated by simply adjusting the pH of milk to be sufficiently acidic that the isolated casein is insoluble in water, alcohol and ether, both dissolves in alkaline and some acidic solution. – a nutrient protein has energy that can be realeased during metabolism – cleavage of unstable phosphate group release the energy C. Albumin – protein that is soluble in water and also in moderately conc.