Answer: A. Cytoplasm

Explanation: Collagen is synthesized on ribosomes as pre-pro-collagen. From there it enters the endoplasmic reticulum where the signal sequence is removed from the terminal end and glycosylation and hydroxylation of proline and lysine residues occur, resulting in the formation of procollagen. From endoplasmic reticulum it is secreted extracellularly through the golgi apparatus. Here the extracellular enzymes cleaves the extension peptides and finally the triple helical collagen moleculs assemble into collagen fibers.

Reference: Harper’s Principles of Internal Medicine, 25th Edition, Page 697 and 29th Edition, Chapter 48 ; Lipppincott Biochemistry, 2nd Edition, Page 40 ; Vasudevan Biochemistry, 4th Edition, Page 240

Answer: C. Ca++

Explanation: Tropocollagen is the basic molecular unit of collagen fibrils and is found in the interstitial spaces. Tropocollagen is a rod shaped molecule which is 300 nm long and 1.5mm thick. There is a 40nm gap between the linearly arrayed proto collagen units. This gap serve as nucleation site for hydroxyapatite(calcium phosphate gel) during bone formation.

Type I collagen: skin, bone, tendon, cornea
Type II collagen: cartilage, intervertebral disks
Type III collagen: blood vessels, lymph nodes, dermis, early phases of wound repair
Type X collagen: epiphyseal plates
Type IV collagen forms flexible, sheetlike networks and is present within all basement membranes.

Reference: Biochemistry By John W. Pelley, page 22.