Cell Communication

A.P. Biology Ch. 11

Goals & Objectives• Describe in writing important communication

pathways for a cell• Describe in writing how each pathway works

Big Idea• How do you get a message from outside the

cell to inside?– Cell growth, cell division– Nerve cells

• Chemical messages are communicated by changing the shape of certain molecules– Change shape, trigger a response– “On/Off” switch

Local vs. Long Distance “Calling”

How Cell Communication Works

• Telephone Analogy

Caller (your friend)

Phone Tower/Switchboard

Parent

YouCaller = Ligand (chemical signal)

Phone Tower/Switchboard = Receptor protein in cell membrane (outside cell)

Parent = Membrane bound protein (inside cell)

You = Desired cell response

3 Phases in Cell Communication

(ligand)

Using a Chemical Signal• Ligand docks with receptor protein in

membrane, causes shape change– Often caused by phosphorylation– Returns to original shape when ligand detaches

• Change in receptor protein causes a chain reaction of shape changes in other proteins– Signal Cascade– More phosphorylation (ATP ADP + P)– Signal can be “amplified;” (think spam e-mail)

Example of a Signal Cascade

**Notice that the addition of a phosphate causes shape change in protein kinase

3 Types of Cell Communication • G protein

– Single communication within membrane

• Tyrosine kinase– Many signals (amplification)

• Ion Channels– Allows flow of ions into/out of cells

G Protein• Uses GTP

(similar to ATP)

• Completely membrane bound

• Examples:– Hormones– Neurotransmitt

ers– Epinephrine

Tyrosine Kinase• Combining of two

proteins, can phosphorylate 6 ATP at a time

• Massive phosphorylation causes multiple responses

• Cell growth/division

Ion Channel• Ligand causes protein

channel to open/close

• Ion flow causes cell response

• Nerve impulse/Nervous system

Apoptosis• Programmed cell death (suicide)

• Triggered many different ways– Mitochondrial chemicals/molecules– Nuclear chemicals/DNA damage

• Necessary for development of an organism– Development of limbs– Get rid of cells that are harmful