Cell Bio Unit 3 Chapter 7 Cell Interactions

What is a glycocalyx?

The “cell coat” on the outer surface of the plasma membrane.(It is a gel-like, sticky later made of sugars and proteins)

What is an ECM?

a interconnected network of molecules and filaments that provide structure to cells and surrounding tissues. It also helps with cellular activities.

What is a basement membrane?

it is a dense layer of ECM that sits below epithelial and endothelial cells.

What are the functions of a basement membrane? ** still kinda unsure

The basement membrane separates the cells from connective tissues, muscle, and fat. Surrounds nerve cells, muscle cells, an fat cells.

What are some of the protein components of the ECM?

collagen, fibronectin, laminin, proteoglycans, and integrins

What are collagens?

• a family of fibrous glycoproteins

• only found in the ECM

• resist pulling forces

• can hold a lot of weight without breaking

• triple helix structure

What are Fibronectins?

• a LARGE protein in the ECM

• has a bind site for other ECM components (collagens, proteoglycans, other fibronectin mcs)

• are bid site for receptors on cell surface

• a polypeptide chain

• double helix structure

What are proteoglycans?

• HUGE protein-polysaccharide complexes

• take up a lot of ECM space

• have a core protein molecules with many disaccharide chains branching from it (GAGs)

What is hyaluronic acid?

the core protein of proteoglycans. Where the GAGs attach to

What are GAGs?

• chains of disaccharides that branch from a core protein

• core protein + many GAGs = proteoglycan

• Can be keratan sulfate or chondroitin sulfate

What are laminins?

• family of ECM glycoprotein

• 3 different polypptide chains (disulfide bonds)

• T-shaped molececules

• influence cell migration, growth, and differentiation

• binds to cell-surface receptors

• bind to other laminin molecules

What do matrix metalloproteinases do?

• they are zinc-containing enzymes

• degrade ECM and cell surface protein material

How do integrins function?

• membrane proteins

• bind cites for receptors

• bind ECM ( grab ligands on the outside of the cell) and intracellular environment ( attach to proteins on the inside of the cell)

• look a bit like salad tongs and can grab ECM elements like collagen to secure it from moving around too much

What are focal adhesions?

• mostly seen in vitro

• assists integrin to make connection between ECM and cytoskele

• when cell attaches to the bottom of a petri dish, it flattens itself out and anchors itself in certain spots on the dish. Those spots are the focal adhesions

What are hemidesmosomes?

• assists integrin to make connection between cytoskele and ECM

• similar to focal adhesions, just not in vitro

• tightest attachment between cell and ECM

• cells anchor to basement membrane with hemidesmosome

• a plaque that holds IFs, proteins, and other things

What are the 4 integral membrane proteins that mediate cell-cell adhesions?

• selectins

• certain IgSF proteins

• certain integrin proteins

• cadherins

What do selectins do?

• family of integral membrane glycoproteins

• attach to end of oligosaccharide chain

• they are cell surface receptors

• mediate adhesion of white blood cells to endothelial cells and platelet flow?? **unsure

What do IgSF proteins do?

• AKA immunoglobulin superfamily

• mediate cell-cell adhesion

What are cadherins (describe)?

• family of glycoproteins

• can transmit signals from ECM to cytoplasm

• mediate Ca2+ dependent cell-cell adhesions

• make up the “bridge” that connected one cell to another adherins junctions

What are adherins junctions (describe structure)?

• adherins junction + desmosome on both cells, connected by cadherins

• binds to actin filaments (not directly but you get the idea)

What are gap junctions (describe strucuture)

• in epithelial cells

• act as a tunnel where some ions can pass thru

• only in animals

• connexin/connexon make up the gap function and can open and close as necessary

What are tight junctions (describe structure)?

• one molecule of claudin

• one molecule of occludin

• claudin and occludin span the gap between cells

• binds to actinomyosin (like adherins junctions bind to actin)

What are desmosomes (describe structure)?

• disk-shaped adhesive junctions that are on the inner portion of two cell membranes

• cadherin-like molecules span the gap between two cells (like in adherins junctions)

• bind keratin filaments (like adherins junctions bind actin)

What type of junctions form the blood-brain barrier?

• tight junctions

• creates a tight seal so water doesn’t get through

What are connexins? What are connexons?

• associated with Gap junctions

• pass commpletely thru lipid bilayer

• Connexins are the smaller subunit that make up the connexon

• there are 6 connexins to ever connexon

• flower shape

What are tunneling nanotubes?

• a form of long-range communication

• connects cell surface proteins, vesicles, organelles from two cells that are far away