Module 1 Lecture 5: Cell Adhesion Molecules & Membrane Transport Flashcards
Other than creating a protective behaviour and housing internal structures of the cell, what does the plasma membrane do?
Involved in cell to cell adhesion
By what means are cells held together?
Cell Adhesion Molecules (CAM), Extracellular Matrix (ECM), Specialized cell junctions
What are cell adhesion molecules?
Help stick one cell to another cell; not as strong as other methods but mainly used for signalling
What is the extracellular matrix?
Found in between two cells (in respect to tissue); it is filled with fibrous proteins embedded in interstitial fluid
What is the interstitial fluid used for?
Provides a path to help diffuse nutrients, wastes and other soluble traffic between blood and tissue cells
There are three proteins fibres apart of the extracellular matrix. Where are they woven through?
Through the interstitial fluid
What are the protein fibres of the extracellular matrix called?
Collagen, Elastin, Fibronectin
What is collagen fibre?
Most abundant protein in the body; forms cable-like fibres and used for mechanical strength
What is elastin?
Elastic/rubbery protein fibre; for tissues that need to stretch and recoil (i.e. lungs)
What is fibronectin?
Helps hold cells in position; promotes cell adhesion
How is fibronectin linked to tumour metastasis?
Tumour cells metastasize when they get out of control and they destroy the fibronectin that holds them in place
What is the ECM serve as?
Biological glue holding cells within tissues together but not letting them touch
Which tissue is the ECM more abundant in? What secretes ECM?
Connective tissue; fibroblasts secrete ECM
What do fibroblasts make in connective tissue?
The ECM’s structural proteins - collagen, elastin and fibronectin
What are specialized cell junctions molecules
Help link cells together; either touching or not and each one of them are special to certain tissues
What are the three specialized cell junctions named?
Desmosomes, Tight Junctions, Gap Junctions
What are desmosomes? What are they most abundant in?
Adhering junctions; tissues subject to considerable stretching (skin, heart, uterus)
What is the basic function of a desmosome?
Act like an anchor for two adjacent but non-touching cells
Describe how desmosomes connect two cells without ripping it apart?
1) There are plaques on the cytoplasmic side of the plasma membrane; they help strengthen the fluid membrane on both sides of each cell
2) Intercellular filaments (a.k.a. cadherins) connect the cells to the plasma membrane and the plaque inside the cell increasing the rigidity of the membrane
3) Finally, the intracellular filaments (i.e. intermediate filaments) that are connected inside the cell relieve pressure on the membrane.
What part(s) of the two adjacent cells connected is the desmosome formed from?
From the plaque end inside one cell, to the intercellular filaments to the beginning plaque inside the adjacent cell
Would you be able to rip apart a desmosome junction?
No; strongest cell-to-cell connection
What are tight junctions?
Adjacent cells where the plasma membranes are stitched together to seal off passageway between two cells
An example of why tight junctions are important?
The intestinal lining for example; if it had any loose areas then it would be leaking + the possibility of other substances going into our gut would not be beneficial
What’s the purpose for tight junctions?
Block off passage of molecules between cells; only passage way is through the cell membrane
Where are tight junctions commonly found?
Primarily in sheets of epithelial tissue like the ones covering the body and line internal cavities
What are tight junctions also known as?
Impermeable barrier
How strong are tight junctions?
Not as strong as desmosomes; can rip off if it wants to
What are gap junctions? What are they used for?
Junctions between two adjacent cells that transport small molecules and ions between them
What forms gap junctions?
Connexons; small connecting tunnels
Where are gap junctions abundant in?
Cardiac muscle and smooth muscle; where rhythmic contractions must be kept
How do gap junctions help in synchronized contractions of a whole muscle mass?
Movement of ions helps transmit electrical activity
Permeability, Impermeability, Selective Permeability
Plasma membrane classified into three types of permeableness
What properties influence whether a substance can permeate the plasma membrane without help
1) Solubility of the particle in lipid
2) Size of the particle
What molecule can easily permeate the membrane
small + Fat soluble molecule (O2)
What are the two forces required to move a molecule across its gradient?
Passive force and active force
What are passive forces?
Does not require the cell to use energy
What are active forces?
Requires the cell to use energy
