Which of the following is incorrect?
(a) The hair protein, keratin, is synthesized from the amino acid methionine
(b) Phospholipids act as carriers of inorganic ions across the cell membrane
(c) Dietary intake of PUFA increases the serum cholesterol level in our body
(d) Cobalt is a constituent of Vit B12
(a) Keratin is an insoluble, sulfur-containing fibrous protein that serves as the main structural molecule in hair and nails and is also present in the skin. Keratin is synthesized by cells known as keratinocytes and may be hard or soft. hard keratin is found in hair and nails, soft keratin is found in the epidermis of the skin in the form of flattened non-nucleated scales that slough continually. The main differences in various keratins arise from their sulfur content. If there are many cysteine disulfide cross-links, then there is very little flexibility as in horns, claws, hooves or nails. In wool, skin and muscle proteins, there are fewer disulfide cross-links which allows some stretching but returns to normal upon relaxation of tension.