Biology Unit 4 Topic 1-4: Cell Communication, Introduction to Signal Transduction, Signal Transduction, and Changes in Signal Transduction Pathways

direct contact

communication through cell junctions to allow signals and other material dissolved in the cytoplasm to pass freely between adjacent cells

gap junction

animal cell direct contact, connection between the cytoplasm of 2 cells

plasmodesmata

plant cell direct contact, through microscopic channels that travel through the inner walls

hormones

chemical messengers made by multicellular organisms that travel through fluids to target cells or organs to regulate processes and behaviors

Fill in the blanks: In direct contact communication, animal cells communicate through ______ junctions and plant cells communicate through ________.

gap, plasmodesmata

What do animals and plants use for long distance signaling?

hormones

Differentiate between animals and plants when they use long distance signaling to communicate.

plants-release hormones that travel in the plant vascular tissue (xylem and phloem) or through the air to reach target tissues

animals-use endocrine signaling by releasing hormones into the circulatory system to reach target cells

Differentiate between paracrine signaling and synaptic signaling.

paracrine-excretory cells release local regulators (i.e growth factors) through exocytosis to an adjacent cell

synaptic-occurs in the animal nervous system, neurons secret neurotransmitters across the synaptic cleft

True or false: insulin signaling is an example of local signaling.

false; insulin is used in long distance signaling

reception

stage 1 of cell signaling

1. ligands are detected and received by receptor in target cell

2. causes conformational change that activates the receptor

3. can interact w/ other cellular molecules

transduction

stage 2 of cell signaling

1. extracellular signal is converted into an intracellular signal

2. requires a sequence of changes in the signal transduction pathway

3. amplifying the signal w/ help of 2nd messengers

receptor

macromolecule w/ an area that binds to a ligand and an area that transmits a signal to another protein

ligand

signal molecule that binds to a specific receptor to transmit a signal into or between cells

second messengers

small non-protein molecules and ions that help relay the message and amplify the response in transduction

GPCR

largest category of cell surface receptors important in animal sensory systems

binds to a G protein that can bind to GTP

enzyme is activated

signal is amplified and cellular response occurs

ligand-gated ion channel

important receptor for nervous system

acts as a gate for ions in the plasma membrane

allowing diffusion of specific ions

protein kinase

in protein regulation in signal transduction pathway

protein enzyme causes phosphorylation

relays signals

protein phosphatase

in protein regulation in signal transduction pathway

protein enzyme causes dephosphorylation

shuts off pathways

cAMP

common 2nd messenger synthesized from ATP

relays messages and amplifies the responses of cells

response

last stage of cell signaling

1. final molecule in signaling pathway converts signal to a response

2. alters a cellular process

Summarize the three stages of cell signaling in one sentence each.

reception-ligands received by a receptor, activated through a conformational change and initiates a transduction signal

transduction-extracellular signal converted into intracellular signal; amplified to bring out a cellular response using signal transduction pathway

response-final molecule in signaling pathway converts the signal to a response; alters a cellular response

If you were given a problem on the AP exam that described a water-soluble (polar) receptor, where would it be located in the cell?

plasma membrane

Receptors that bind to estrogen, a hormone, would be found where in the cell?

cytosol or nucleus of the target cell

What do second messengers do, and why is this role so important in some cells?

help relay the messages and amplify the cellular response

act as intermediaries to convert a signal from a hormone or other external molecules into a sequence of internal cellular actions

Differentiate between the role of protein kinase and protein phosphatase in cells.

kinase-used in phosphorylation, relays signals

phosphatase-used in dephosphorylation, shuts off pathways

What does the term “signal” refer to in a signal transduction cascade?

the ligand

Neurons can participate in both local and long distance signaling. How is this possible (you may do research online to help answer this question if needed)?

has short dendrites and long axons

local signaling-neurotransmitters diffused over the short distance of synaptic cleft

long distance signaling-axon transmits an electrical impulse over large distances to target cell

How are signals passed from outside of the cell to inside of the cell?

through receptors in phospholipid bilayer as ligand attaches to it and allows signal to pass

Describe the “response” that a cell can have to a signal.

1. protein that can alter membrane permeability

2. enzyme that will change a metabolic process

3. protein that turns genes on or off

How is it possible that a single signal molecule can elicit massive cellular responses?

the signal transduction pathway opens from the ligand receptor

What is transcription and translation (as it pertains to DNA)?

transcription-a DNA segment is copied into a mRNA

translation-using amino acid sequences in mRNA to synthesize proteins

True or false: the final molecule in a signal transduction pathway can act as a transcription factor, meaning that it can turn genes off or on.

true

What does it mean if a gene is turned off vs on?

on-production of a protein occurs

off-production of a protein ceases

What would happen to the signal transduction pathway if protein phosphatase was mutated?

dephosphorylation cannot occur

cannot shut off pathways

What would happen to the signal transduction pathway if protein kinase was mutated?

phosphorylation cannot occur

cannot relay signal inside cell

If a receptor protein is mutated, can it receive a ligand? Why or why not?

no, bc binding between them is highly specific

How can chemicals activate or inhibit a pathway? (i.e what does “activate” mean and what does “inhibit” mean in terms of a signaling cascade?)

once ligand binds to the receptor, causes a conformational change that activates the receptor

inhibited during dephosphorylation bc it shuts off pathways