Question

Question #1 & #2 should be separate illustrations, each contained within one sheet

of paper.

1.Within the context of a cell,illustrate the progressive stages that lead to assembly of procollagen

.Your diagram should begin with the translation of the alpha -chain mRNA on ribosomes in the cytosol. Use numbers or arrows to indicate the sequence of events. Label the compartments and macromolecules involved in the process. Your diagram should include critical post–translational modifications required for procollagen formation and indicate when GTP associates with various macromolecules.Be sure to represent conformational changes in the SRP, SRP-receptor, and translocon.

2.Starting with procollagen in the Golgi, illustrate the progressive stages that lead to assembly of collagen fibers.Use numbers or arrows to indicate the sequence of events. Label the compartments and macromolecules involved in the process

Answer 1

Collagen being the largest component of ECM (extracellular membrane) ,most abundant protein in our body provides tensile strength to tissues & organs as well as forms the structural framework of connective tissues such as bone, tendon, dermis. Post translation modification of collagen consists of 2 stages i.e. (a) intracellular modification (synthesis of polypeptide chain,resulting in formation of triple helical procollagen molecule.

(b) Extracellular modification ( convert these molecules into collagens & assemble them into stable crosslinked fibrils)

This diagram above is the explanation of part 2. Which indicates the process of formation of collagen fibrils within the cell & it's transport by Golgi bodies.

Procollagen (soluble precursor of collagen) synthesis is initiated in ER & continue within the narrow infolds of P.M (plasma membrane) which are continuous with extracellular space.

A procollagen molecule has 3 alpha polypeptide chain where the alpha chain is left handed.SRP binds to secretory proteins coming from ribosomes where it forms a ribosome-nascent chain ( RNC) - SRP complex which helps in the translation of particular polypeptide. Translocon helps in the translocation of polypeptide across membrane during collagen formation. GTP is being utilised at that point

picture above describes the step wise formation of procollagen. (Answer to first part of question)