ap bio cell communication

apoptosis pathway

when there’s a death signal:

-death signal binds to receptor. this causes CED-9 to become inactive

when CED-9 is inactive, it’s not there to stop CED-3 and 4
-CED-4 activates CED-3, which triggers a phosphorylation cascade

which…

-makes caspases (proteases that digest cell’s proteins)
-forms blebs (vesicles of digested cell)

apoptosis

means “cell suicide“

what happens?
-cell is chopped up, then packaged into vesicles

but why is it in vesicles?

-prevents other cells from taking in organelles

response

-after the signal travels the transduction pathway, it causes a specific response.

-cell proteins determine how it reacts to this signal

2nd messenger

-function: continues cellular response

-it is usually a small, nonprotein, water soluble particle
(cAMP, IP₃, GGMP, Ca²⁺)

-usually involved w G-proteins
-it causes the phosphorylation cascades which amplify signal

transduction

-involves signaling cascades to amplify the signal for a response
-this is the process before the response 

-uses a second messenger to carry signal which causes he phosphorylation cascade.

G-Protein receptor

-ligand bonding causes a conformational change

-conformational change pushes the active g-protein away so that it’ll activate another enzyme or protein channel

-involves GDP and GTP

ligand gated ion channel

-channel in cell membrane is closed (hence, gated) without the ligand

-ligand must bind for the channel to open

-only specific ions pass through it’s specific channel

RTK (receptor tyrosine kinase)

-ligand binds to this receptor and the receptor becomes a dimer

-each dimer phosphorylates multiple tyrosine on other RTKs throughout the cell. this causes transduction to begin!

reception

-a receptor protein binds to a ligand to cause conformational change

-the completion of this stage initiates the transduction stage

signal transduction

where an extracellular signal is converted into an intracellular response

intermembrane receptors

-signaling molecules are CHARGED and POLAR

-receptors are IN the cell MEMBRANE

intracellular receptors

-signalling molecules are NONPOLAR and SMALL (and uncharged)

-receptors are IN the CYTOPLASM or NUCLEUS

-activated hormone-receptor complex acts as a transcription factor and turn on gene expression!

**DNA → RNA → proteins

stages to cell communication

1. reception

2. transduction

3. response

endocrine

LONG DISTANCE signaling and INSIDE secreting

-cell releases hormone that travels to cell somewhere else in an organism.

-specific hormone only binds to a specific receptor

paracrine

NEXT TO SECRETING and SHORT DIST signalling

-one cell secretes hormones or molecules that bind to ANOTHER, nearby cell’s receptors

think: neurons and neurotransmitters

autocrine

SELF SECRETING and SHORT DIST signaling
-releases molecules which binds to its own receptors