Module 1: Lecture 5 Flashcards
what are the three main forms of cell-to-cell adhesions? (keep the tissue together)
- Cell Adhesion Molecules (CAMs)
- The Extracellular Matrix (ECM)
- Specialized cell junctions
what helps cells stay in place and give tissue strength so that it cant pull apart and helps tissue stretch and recoil?
the long cables of proteins and fibers that sit in the extracellular matrix that cells will attach to
specialized cell junctions are called specialized because why?
they are in specialized tissues and they have a specialized function
what are the three different types of extracellular matrix proteins?
- collagen: gives the tensile strength
- elastin: stretches and recoils
- fibronectin: holds cells in place
what is the extracellular MATRIX?
an intricate meshwork of fibrous proteins embedded in a watery, gel-like substance (aka, interstitial fluid) composed of complex carbohydrates
what is the interstitial fluid?
the fluid between cells in a tissue (technically extracellular fluid just looking from a tissue perspective instead of a cellular perspective)
what is 1/2 the weight of protein content in the body?
collagen
reduced levels of fibronectin is linked to what?
tumor metastasis
what cells make the extracellular matrix?
fibroblasts
what are cell adhesion molecules (CAMs) for?
they are membrane proteins that allow two cells to interact and hold onto each other (Velcro)
what are the three types of specialized junctions?
- desmosomes (adhering junctions)
- tight junctions (impermeable junctions)
- gap junctions (communicating junctions)
what is the job of desmosomes (adhering junctions)?
- provides two cells with the strongest form of adherence of sticking together
what is tight junctions (impermeable junctions) for?
- for the two cells that you do not want anything between or inside it (no space between them)
what is the job of gap junctions (communicating junctions)?
- allow cells to be able to communicate at an instantaneous rate (zero delay)
how does a desmosome anchor together two cells?
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
where will you find desmosomes?
tissues and organs that are subject to extreme mechanical pressure
how does tight junctions (impermeable junctions) form the impermeable barrier?
adjacent cells firmly bind together at points of contact to seal off the passageway between the two cells
when is a tight junction needed?
in sheets of epithelial tissue
- anywhere to prevent bacteria from crossing
where are gap (communicating) junctions abundant mostly in?
cardiac muscle and smooth muscle (CONTRACTING AT EXACT SAME TIME)
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?
ions need to flow freely between those cells. this is done with tunnels called gap junctions
gap junctions are formed by?
proteins called connexons
what is the diameter of the gap junction?
1.5 nanometers (only ions can cross)
is a plasma membrane permeable?
no. its selectively permeable.
what does selectively permeable mean?
selects what can and cant get into the cell depending on the property of the molecule and composition of the membrane
what are the two properties that influences whether a substance can permeate the plasma membrane WITHOUT any assistance?
- solubility in lipid (uncharged or nonpolar molecules)
- size of particle (smaller moves faster)
ex. oxygen is probably fastest because its lipid soluble and small
is solubility two extremes?
no. most molecules are on a spectrum
how is glucose allowed into a cell?
carriers. the GLUT-transporter (assisted transport)
- it will carry glucose from one side and bring it to the other side (assisted transport)
what is the difference between active and passive force?
active: forces that require the cell to expend energy
passive: forces that does not require the cell to spend energy
