Module 1: Lecture 5

Question 1

what are the three main forms of cell-to-cell adhesions? (keep the tissue together)

Answer 1

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

Question 2

what helps cells stay in place and give tissue strength so that it cant pull apart and helps tissue stretch and recoil?

Answer 2

the long cables of proteins and fibers that sit in the extracellular matrix that cells will attach to

Question 3

specialized cell junctions are called specialized because why?

Answer 3

they are in specialized tissues and they have a specialized function

Question 4

what are the three different types of extracellular matrix proteins?

Answer 4

• collagen: gives the tensile strength
• elastin: stretches and recoils
• fibronectin: holds cells in place

Question 5

what is the extracellular MATRIX?

Answer 5

an intricate meshwork of fibrous proteins embedded in a watery, gel-like substance (aka, interstitial fluid) composed of complex carbohydrates

Question 6

what is the interstitial fluid?

Answer 6

the fluid between cells in a tissue (technically extracellular fluid just looking from a tissue perspective instead of a cellular perspective)

Question 7

what is 1/2 the weight of protein content in the body?

Answer 7

collagen

Question 8

reduced levels of fibronectin is linked to what?

Answer 8

tumor metastasis

Question 9

what cells make the extracellular matrix?

Answer 9

fibroblasts

Question 10

what are cell adhesion molecules (CAMs) for?

Answer 10

they are membrane proteins that allow two cells to interact and hold onto each other (Velcro)

Question 11

what are the three types of specialized junctions?

Answer 11

• desmosomes (adhering junctions)
• tight junctions (impermeable junctions)
• gap junctions (communicating junctions)

Question 12

what is the job of desmosomes (adhering junctions)?

Answer 12

• provides two cells with the strongest form of adherence of sticking together

Question 13

what is tight junctions (impermeable junctions) for?

Answer 13

• for the two cells that you do not want anything between or inside it (no space between them)

Question 14

what is the job of gap junctions (communicating junctions)?

Answer 14

• allow cells to be able to communicate at an instantaneous rate (zero delay)

Question 15

how does a desmosome anchor together two cells?

Answer 15

intercellular filaments (cadherins) join the two cells together by going through the plasma membranes, and attaching to a cytoplasm thickening which is a plaque that sits on the intracellular side of the plasma membrane. On that plaque, intracellular keratin (which is very very strong) filaments connect and then travel all throughout the cell to make sure it is all connected together

Question 16

where will you find desmosomes?

Answer 16

tissues and organs that are subject to extreme mechanical pressure

Question 17

how does tight junctions (impermeable junctions) form the impermeable barrier?

Answer 17

adjacent cells firmly bind together at points of contact to seal off the passageway between the two cells

Question 18

when is a tight junction needed?

Answer 18

in sheets of epithelial tissue
- anywhere to prevent bacteria from crossing

Question 19

where are gap (communicating) junctions abundant mostly in?

Answer 19

cardiac muscle and smooth muscle (CONTRACTING AT EXACT SAME TIME)

Question 20

what do ions needs to do between cells if you want every single cell in a tissue to contact at the exact same second? how is this done?

Answer 20

ions need to flow freely between those cells. this is done with tunnels called gap junctions

Question 21

gap junctions are formed by?

Answer 21

proteins called connexons

Question 22

what is the diameter of the gap junction?

Answer 22

1.5 nanometers (only ions can cross)

Question 23

is a plasma membrane permeable?

Answer 23

no. its selectively permeable.

Question 24

what does selectively permeable mean?

Answer 24

selects what can and cant get into the cell depending on the property of the molecule and composition of the membrane

Question 25

what are the two properties that influences whether a substance can permeate the plasma membrane WITHOUT any assistance?

Answer 25

• solubility in lipid (uncharged or nonpolar molecules)
• size of particle (smaller moves faster)
  ex. oxygen is probably fastest because its lipid soluble and small

Question 26

is solubility two extremes?

Answer 26

no. most molecules are on a spectrum

Question 27

how is glucose allowed into a cell?

Answer 27

carriers. the GLUT-transporter (assisted transport)
- it will carry glucose from one side and bring it to the other side (assisted transport)

Question 28

what is the difference between active and passive force?

Answer 28

active: forces that require the cell to expend energy
passive: forces that does not require the cell to spend energy