Ch 11: Cell-Cell Interactions

What are the four types of cell junctions

Tight junctions

Desmosomes

Gap Functions

Plasmodesmata

describe tight junctions

Seals cells together with a water tight seal between adjacent cells

prevents molecules from passing

Found between epithelial cells (lungs, intestines)

Sometimes looks like membrane proteins bind to one another to form the tight junction

Describe desmosomes

Connects the cytoskeletons of cells by strong adhesion

Continuous structural support between cells

In tissues that experience intense mechanical stress (bladder, cardiac muscle, epithelia)

Describe Gap functions

Act as channel between cells

Protein channels between adjacent cells

Allows direct communication between cells (rapid passage of ions or small molecules)

the membrane proteins literally line up to create a channel

Describe plasmodesmata

ONLY FOUND IN PLANTS

Gaps in cell walls

NO proteins involved

Continuous plasma membrane and cytoplasm

What are the four steps of cell-cell signaling in order

1. Signal reception

2. signal processing

3. signal response

4. signal deactivation

Describe signal reception and signal receptors

Signal receptors are protein that change shape and activity after binding for a signal molecule

With lipid-soluble molecules:

Diffuse across cell membrane; bind to receptors in the cytosol; transported to nucleus to affect the transcription of DNA

With Lipid-Insoluble molecules:

The signal molecule binds; receptor undergoes conformational charge; receptor activates signal transduction inside the cell

Explain further detail signal transduction

could have

Second messenger : small molecules relay intracellular signals ; cAMP activates kinases; ions

Phosphorylation Cascade:

each kinase phosphorylates a different kinase until a response is triggered

what is kinase

enzyme that adds phosphate groups to other molecules

speeds up chemical reactions

signal processing

ig that’s part of the last stuff we went over

the second messengers or phosphorylation cascade

describe signal response

typical responses:

bind to DNA to change gene expression; increase or decrease protein production

OR
Change in the activity of proteins in the cell

Describe signal deactivation

Different for different signal types

review the lecture

did you actually review it like be fr