Question

1- Proteoglycans are different from peptidoglycans and glycoproteins in that proteoglycans:

a. are primarily chains of polysaccharides, with each polysaccharide covalently linked to one core protein

b. are primarily chains of polysaccharides that are covalently linked to each other through a few amino acids

c. are primarily proteins that are modified with a few polysaccharides

d. are primarily proteins that are modified with one polysaccharide

2- Which of the following statements about tight junctions is FALSE?

a. Tight junctions are interactions between transmembrane proteins of adjacent cells

b. Tight junctions form barriers between one side of an epithelial cell layer and the other side of the cell layer

c. Tight junctions allow the plasma membranes of adjacent cells to fuse together

d. Tight junctions prevent lipids and membrane proteins from fluidly diffusing around the plasma membrane

3- Which of the following statements about gap junctions is correct?

a. Gap junctions provide adhesive strength between cells

b. Gap junctions create a barrier between the apical and basolateral sides of an epithelial cell

c. Gap junctions allow endoplasmic reticulum membranes to pass through between cells

d. Gap junctions allow for small molecules to pass from one cell directly into another cell

Answer 1

1.proteoglycans are different from peptidoglycans and glycoproteins in that proteoglycans :

a. are primarily chains of polysaccharide with each polysaccharide covalently linked to one core protein.

b.are primarily chains of polysaccharide that are covalently linked to each other through few aminoacids

c.are primarily proteins modified with few polysaccharides

d.are primarily proteins that are modified with one polysaccharide

option - A is incorrect because they are primarily modified proteins , they are made up of one core protein and linear polysaccharide side chains .i.e glycosaminoglycan side chains (GAG - side chains)

These GAG-side chains are covalently linked to core protein .

These GAG-chains are unbranched polysaccharides .and these make up half of the mass of proteoglycans.

The proteoglycans are mucoproteins found in most connective tissues

Option-b is incorrect because polysaccharide chains are not covalently linked to each other .and not linked through aminoacids

They are covalently linked to core proteins.

Option c is correct because they are primarily proteins modified by attachment of one or more GAG - side chains ( polysaccharide units)

option D is inccorect because they are primarily proteins modified with one or more polysaccharides and it is not limited to a single one