Question

Casein contained in milk is-
A. Fat
B. Carbohydrate
C. Protein
D. Bacterium

Answer 1

Hint: These are commonly found in mammalian milk, the highest quantity comprising 80% in cow's milk and between 20% and 45% in human milk. Buffalo and Sheep milk have a higher casein content than other types of milk with human milk having a particularly low concentration of Casein.

Complete answer:
• Casein is a family of phosphoproteins(contains phosphorus attached with protein).
• It has a wide variety of uses, whether being a major component of cheese or as a food additive.
• The most common form is sodium caseinate. It undergoes phase separation in milk to form colloidal casein micelles, a variety of biomolecular condensate.
• Casein contains a high quantity of the proline residue. There are also no disulfide bridges.
• It is found in milk as a suspension of particles, called casein micelle.
• The inside of a casein micelle is hydrated. They are held together by calcium ions in the micelles and hydrophobic interactions.
• One model says that the micellar nucleus is formed by several sub micelles.
• The other model provides evidence that the nucleus is formed by casein-interlinked fibrils.
• The modern model proposes a double link among the caseins for gelling to occur.
• The isoelectric point of casein is estimated to be around 4.6.

Hence, the correct answer is option (C).

Note: Some important points regarding Casein are as under-
• All three models of casein structure laid emphasis on micelles and depict them as colloidal particles formed by casein aggregates wound up insoluble κ-casein molecules.
• Trypsin(an enzyme) can hydrolyze a phosphate-containing peptone. It is used to manufacture a type of organic adhesive.