connective tissue 1 C

Question 1

Fibrillar collagen:

Answer 1

Some collagen molecules assemble in large bundles, called fibrils.

Question 2

How are fibrillar collagen bundles formed?

Answer 2

collagen molecules are aligned both head to tail, to generate length (up to several hundred um long), and they are stacked to generate fibril thickness. These rope-like structures can have great strength to resist tensile stresses in tissues.

Question 3

Collagen fibrils size:

Answer 3

can vary enormously in thickness

Question 4

_____ is an abundant component of fibrillar collagen

Answer 4

Collagen Type I

Question 5

Fibril-associated collagen:

Answer 5

These collagens decorate the surfaces of collagen fibrils, and are thought to link collagen fibrils to each other, or to link collage fibrils to other tissue components.

Question 6

Network-forming collagen form _____

Answer 6

very thin fibers (perhaps a few molecules thick) and assemble into interlaced networks that form porous sheets.

Question 7

network forming collagens are found:

Answer 7

in the basal laminae, and also as anchoring fibers that attach basal lamina and cells to the extracellular matrix.

Question 8

Some of the network forming collagens function ____

Answer 8

as important filtration barriers (as in the kidney).

Question 9

net working forming collagen type

Answer 9

Collagen Type IV is a common component of the network-forming sheets in basal laminae

Question 10

Loose connective tissues contain ____.

Answer 10

thin collagen fibrils that are relatively sparse, and are arranged in irregular lattices

Question 11

where are loose connective tissues found?

Answer 11

Blood and lymph capillaries, as well as nerves, are typically abundant in loose connective tissue.

Question 12

Dense connective tissues contain:

Answer 12

1. thick collagen fibrils that are very abundant relative to ground substance
2. have a low number of cells.
3. can have collagen bundles that are arranged in various “irregular” orientations
4. or arranged in parallel organized sheets like in ligaments and tendons

Question 13

dense CT are found

Answer 13

These tissues also have great strength, and are found where tissues must resist strong shear forces in particular directions, such as in tendons and ligaments

Question 14

Collagen is synthesized and modified ____

Answer 14

intracellularly, and then secreted and further modified extracellularly.

Question 15

Collagen is made and secreted by cells of the ___

Answer 15

connective tissue family.

Question 16

Intracellular collagen synthesis and modification

Answer 16

1. Collagen polypeptides are synthesized on the ER and translocated during synthesis to the ER lumen
2. Collagens are post-translationally modified (they are glycosylated and hydroxylated on selected amino acid residues)
3. The individual polypeptides are assembled into a triple helix

Question 17

extracellular collagen synthesis and modification

Answer 17

1. The N- and C-termini of collagen are cleaved by specific proteases. The N-terminal fragments that are generated are called N-telo peptides. The N-telo peptides are clinically important because their levels in urine and blood are used to diagnose important connective tissue and bone disease. Proteolytic release of these fragments is important to initiate:
2. Formation of bundles and end-to-end polymers of the collagen fibrils
3. Enzymes catalyze chemical cross-links between collagen molecules. These covalent cross-links can increase the tensile strength of the bundles

Question 18

Elastic fibers are found in ____.

Answer 18

connective tissues that require distensibility and resiliency

Question 19

Elastic fibers contain the proteins ____ .

Answer 19

elastin and fibrillin that assemble into stretchable and resilient fibers and sheets.

Question 20

Elastin is a

Answer 20

filamentous protein that exists in a predominantly random coil conformation (i.e. largely unstructured), that can be stretched upon exertion of force

Question 21

Elastin monomers, like collagen, are secreted by ______

Answer 21

fibroblasts (in some cases, smooth muscle cells).

Question 22

Extracellularly, elastic fibers form ______

Answer 22

filaments and sheets where the molecules are highly cross-linked with each other to generate an extensive network.

Question 23

These elastin networks are interwoven with ____

Answer 23

filamentous protein, fibrillin, which appears to help organize the elastin elements in the fiber, and to organize the elastic fibers with the other components of the extracellular matrix. These elastic fibers can stretch and then recoil like a rubber band.

Question 24

ground substance

Answer 24

The structural fibers of the extracellular matrix are enmeshed in hydrated aqueous gelatinous material.

Question 25

major component of ground substance:

Answer 25

1. proteoglycans
2. other secreted proteins and glycoproteins
3. inorganic and small organic solutes
4. water

Question 26

Proteoglycans contain _______.

Answer 26

a protein core attached to very large acidic polysaccharides, called glycosaminoglycans (GAGs)`

Question 27

GAGs are _____

Answer 27

long polymers of carbohydrate molecules (polysaccharides). These molecules typically contain hundreds to thousands of sugar residues.

Question 28

There are several different GAGs; most are ______

Answer 28

covalently attached to proteins, but some like hyaluronic acid are not attached to a protein core.

Question 29

Proteoglycans are

Answer 29

different from other glycoproteins because the GAG chains can be up to 95% of their mass.

Question 30

Three properties of GAGs are relevant to their function:

Answer 30

(1) they are highly negatively charged.
(2) Their rigid extended structure causes them to readily form gels. (3) Some proteoglycans can also bind to and inactivate or activate other proteins, particularly growth factors and ECM modifying enzymes.

Question 31

Because GAG’s are very negative, they are

Answer 31

very hydrophilic

Question 32

GAGs promote _____.

Answer 32

hydration of the ground substance to allow diffusion of small metabolites but tend to inhibit the movement of large structures (like bacteria)

Question 33

Because GAGs promote hydration, they can function as:

Answer 33

selective sieves by forming gels of varying pore sizes.
It also creates a high swelling (turgor) pressure that allows the ECM to resist large compression forces (in contrast to collagen which functions to resist stretching forces).

Question 34

Other secreted proteins and glycoproteins include

Answer 34

1. proteases that process collagen and other types of proteins
2. a variety of other extracellular enzymes
3. growth factors
4. other polypeptide ligands involved in cell signaling

Question 35

Inorganic and small organic solutes: including

Answer 35

1. ions
2. carbohydrates
3. lipid vesicles
4. aggregates
5. non-protein signaling ligands.

Question 36

___ helps to maintain the hydration of ECM

Answer 36

gags