FIBROUS PROTEINS

Question 1

is the most abundant protein in the human body.
is a long, rigid structure in which three polypeptides (referred to as α chains) are wound around one another in a rope-like triple helix
In vitreous humor of the eye: gives support to the structure.
In tendons: bundled in tight, parallel fibers that provide great strength.

Answer 1

COLLAGEN

Question 2

TYPES OF COLLAGEN

Answer 2

Fibril-forming collagens
Network-forming collagens
Fibril-associated collagens

Question 3

have the rope-like structure. In the electron microscope, these linear polymers of fibrils have characteristic banding patterns, reflecting the regular staggered packing of the individual collagen molecules in the fibril.

Answer 3

Fibril-forming collagens:

Question 4

(composed of collagen fibrils): most common collagen; found in supporting elements of high tensile strength (eg: tendon and cornea)

Answer 4

Type I

Question 5

restricted to cartilaginous structures.

Answer 5

Type II:

Question 6

prevalent in more distensible tissues (eg: blood vessels)

Answer 6

Type III

Question 7

Types IV and VIII form a three-dimensional mesh, rather than distinct fibrils. For example, type IV molecules assemble into a sheet or meshwork that constitutes a major part of basement membranes.

Answer 7

Network-forming collagens:

Question 8

types IX and XII bind to the surface of collagen fibrils, linking these fibrils to one another and to other components in the extracellular matrix.

Answer 8

Fibril-associated collagens

Question 9

Collagen is rich in ____ and ____

Answer 9

proline and glycine

Question 10

facilitates the formation of the helical conformation of each α chain because its ring structure causes “kinks” in the peptide chain.

Answer 10

Proline

Question 11

smallest amino acid; found in every third position of the polypeptide chain.

Answer 11

Glycine

Question 12

is essential for the formation of the triple helix structure of collagen.

Answer 12

Hydroxylation

Question 13

a process by which vesicles containing the collagen molecules are transported to the cell membrane and then released to the extracellular space

Answer 13

Exocytosis

Question 14

is the process by which collagen is broken down into smaller molecules. This process is essential for the normal turnover of collagen, which is constantly being produced and degraded in the body.

Answer 14

Collagen degradation

Question 15

a group of connective tissue disorders that result from inheritable defects in the metabolism of fibrillar collagen molecules.

Answer 15

Ehlers-Danlos syndrome:

Question 16

is a genetic disorder of bone fragility characterized by bones that fracture easily, with minor or no trauma.

Answer 16

Osteogenesis imperfecta

Question 17

is a connective tissue protein with rubber-like properties.

Found in the lungs, the walls of large arteries, and elastic ligaments.

They can be stretched to several times their normal length but recoil to their original shape when the stretching force is relaxed.

Answer 17

elastin

Question 18

is an insoluble protein polymer synthesized from a precursor, tropoelastin, which is a linear polypeptide that are primarily small and nonpolar (for example, glycine, alanine, and valine).

Answer 18

Elastin

Question 19

is the most abundant amino acid in elastin, making up about 35% of the protein.

Answer 19

Glycine

Question 20

impaired structural integrity in the skeleton, the eye, and the cardiovascular system.

Answer 20

Marfan syndrome:

Question 21

resulting from α1-antitrypsin deficiency: is a chronic lung disease that causes the air sacs in the lungs to break down and lose their elasticity

Answer 21

Emphysema