Chapter 11: Cell Communication

Quorum sensing

Bacteria secrete signaling molecules (inducers) that bind to receptors, activating transcription of certain genes.

biofilm formation

Signaling leads to the secretion of extracellular polymeric substances (EPS) or slime.

Yeast

Mating type a cells produce a factors, while mating type α cells produce α factors; binding initiates growth toward the signal sender.

gap junctions; plasmodesmata

_____in animal cells and ______in plant cells allow direct movement of signaling molecules dissolved in cytosol for direct communication in multicellular eukaryotes.

paracrine signaling

Local signaling where cells signal nearby cells, often involving growth factors that stimulate cell division.

synaptic signaling

A form of local signaling involving neurotransmitters that transmit signals across synapses.

hormones

______ travel long distances to signal target cells, such as insulin produced in the pancreas signaling glucose uptake.

What are the three stages of cell signaling?

Reception, transduction, and response.

G Protein-Coupled Receptors (GPCR)

Receptors that, upon binding a molecule, exchange GDP for GTP, activating a G protein, cAMP-→ that produces a cellular response.

Receptor Tyrosine Kinases (RTK)

*Tyrone is a self made pimp with 2 hoes

They undergo autophosphorylation(forms dimers) and phosphorylate relay proteins, leading to a cellular response.

ligand-gated ion channels

______ binding causes a conformational change that opens the channel, allowing ions to flow and trigger a cellular response.

sodium-potassium pumps

They are the major electrogenic pumps in animal cells, maintaining membrane potential.

second messenger?

A molecule that relays signals received at receptors on the cell surface, such as cyclic AMP (cAMP) and IP₃, calcium ions.

cAMP

Adenylyl cyclase converts ATP to ______when activated by a G protein.

calcium ions

______ as second messengers are involved in muscle cell contractions, cell division, and leaf greening in response to light.

Inositol Triphosphate (IP3)?

A second messenger involved in calcium ion signaling, triggering the release of calcium from the endoplasmic reticulum.

signal amplification

binding of one molecule to it’s receptor, multiples the signal to produce a greater response

apoptosis

Programmed cell death that can be triggered by external or internal signals, activating a caspase cascade.

specificity in cell signaling

It ensures that signals only affect target cells with the appropriate receptors, preventing unintended responses.

3 steps of cell communication

1. Reception

2. transduction

3. response

Intracellular receptors

-receptors in cytoplasm or nucleus

signal can enter any cell but only effects the cells with the receptors

protein kinase

add phosphate group to protein

protein phosphatase

removes phosphate group from protein

Reception

GPCR, RTK, Ligand Ion

Transduction

• second messengers (cAMP, IP₃, calcium ions)

• protein phosphorylation cascade

Response

cell signalling→ gene expression or cytoplasmic activities

final signal

5 different responses

1. single response

2. multiple responses

3. crosstalk btwn pathways

4. different receptor=different response

5. apoptosis