lecture 5

Question 1

3 types of adhesion by plasma membrane include..

Answer 1

Cell Adhesion Molecules (CAMs)
* The Extracellular Matrix (ECM)
* Specialized cell junctions

Question 2

ECM

Answer 2

looks like a meshwork of fibrous proteins embedded in a watery, gel-like substance made up of complex carbohydrates.

Question 3

interstitial fluid)

Answer 3

provides a pathway for diffusion of nutrients, wastes, and other watersoluble traffic between the blood and tissue cells

Question 4

three major types of protein fibres woven through ECM include

Answer 4

Collagen: Forms cable-like fibers Tensile strength (most abundant
protein in the body! ~½ of total body protein by weight)
* Elastin: Rubber-like protein fiber stretching and recoiling (e.g. in
lungs)
* Fibronectin: Promotes cell adhesion holds cells in position
(reduced levels are linked to tumor metastasis)
Scant in epithelial tissue; abundant in connective tissue secreted by
fibroblasts

Question 5

Cells are directly linked by one of three types of specialized cell junctions:

Answer 5

Desmosomes (adhering junctions)
* Tight junctions (impermeable junctions)
* Gap junctions (communicating junctions

Question 6

Desmosomes

Answer 6

act like “spot rivets” that anchor
together two adjacent but non-touching cells
* Most abundant in tissues that are
subject to considerable stretching
(skin, heart, uterus)
* They are the strongest cell-to-cell
connections

Question 7

Tight junctions:

Answer 7

Adjacent cells firmly bind together at
points of contact to seal off the
passageway between the two cells
* Found primarily in sheets of epithelial
tissue such as those that cover the
body and line internal cavities’
impermeable barrier

Question 8

Gap junctions

Answer 8

A gap exists between adjacent cells,
which are linked by small, connecting
tunnels (formed by connexons
* Communicating junctions (permits
small, water- soluble particles to pass
between the connected cells but
precludes passage of large molecules)
* Abundant in cardiac muscle and
smooth muscle (allow movement of
ions to transmit electrical activity –>
synchronized contraction of a whole
muscle mass

Question 9

what factors determine what can go through the plasma membrane

Answer 9

Relative solubility of the particle in lipid
* Uncharged or nonpolar molecules (O2, CO2, fatty acids) –> Highly
lipid-soluble –> Easy to permeate the plasma membrane
* Charged or polar molecules: ions proteins & glucose –> low lipid
solubility and very soluble in water
size of the particle
* Going through the membrane (lipid-soluble) or through a channel requires
forces to induce the movement.