module 2 (cell signalling + comms) - bio 3 final review

Unicellular and aggregating organisms comms

• sense nutrients and other environmental stimuli

• communicate to coordinate behavior

Multicellular organisms comms

• instruct developmental progression of other cells

• tell a cell to divide (or not)

• communicate to coordinate behavior/responses to many internal and external stimuli

cell signaling pathway

1. recognition (reception)

2. intracellular signaling (relay, signal transduction pathway)

3. effector proteins cause cell response

recognition/reception cell signaling

first step; receptor binds to signal (ligand) = activation of receptor

intracellular receptors

signal goes through cell, binds to receptor inside cell, signal pulled into nucleus of cell by receptor

intracellular signaling (relay, signal transduction pathway)

via intracellular signaling molecules

quorum sensing in bacteria

sense overall cell population density in their surroundings and act accordingly

• symbiotic relationship w/ squid that hunts for food at night + bioluminescent bacteria = camouflage

• cell-cell communication among the bacteria allows them to aggregate and produce light within a compartment of the squid

• signal binds to receptor = transcription of luminescence gene = colonization of germs

Stem cell regulation in Drosophila germ cells

1. support cells produce signal that instructs stem cells to self renew

2. After division, the daughter cell that is farther away doesn’t receive the signal. Stops dividing and progresses toward oocyte differentiation

Complex signal transduction cascades pathway

1. signal to receptor

2. relay signals

3. amplification

4. integration of signals

5. distribution of responses

6. Modulate signals and responses (positive and negative feedbacks)

amplification

signal amplified with intracellular molecules

amplification - enzyme activity

one enzyme can modify many targets (ie. kinase in a pathway can phosphorylate many targets)

amplification

release of second messengers - small molecules made quickly in large quantities; quick diffusion = quick activation of other intracellular signaling molecules

distribution

distribute signal to more than one effector protein

integration

a cell combines multiple, often conflicting, signals into one unified response

feedback

modify the activity of elements upstream of the pathway (ie inhibition)