AP Bio Unit 4 - topics 1-4

Cell communication is responsible for what

Growth/development of multicellular organisms

Cell communicate through three general ways...

Direct contact, local signaling, and long distance signaling

direct contact

communication through cell junctions

In direct contact, signaling substances and other material dissolved in the cytoplasm can...

Pass freely between adjacent cells.

Direct contact, animals

gap junctions

Direct contact, plants

plasmodesmata

Example of direct contact

immune cells

local regulators

Secreting cell that will release chemical messages through extra cellular fluid

2 examples of local regulators?

Paracrine and synaptic

Paracrine signaling

Separatory cell releases messages (via Exocytosis) to adjacent cell

Synaptic signaling

in the animal nervous system; specialized type of local signaling

Neuron secretes neurotransmitters that diffuse across synaptic cleft

long distance signaling

plants and animals use chemicals called hormones

Plants long distance signaling

Release hormones I plant vascular tissue (xylem or pholem) or through air to reach target

Animal long distance signaling

Endocrine signaling:

Specialized cells release hormones into the blood stream ( circulatory system )

Insulin (example of long distance)

Released by pancreas into bloodstream where it circulates in the body

3 steps of cell-to-cell messaging

Reception, transduction, response

Reception

The target cell's detection of a signal molecule coming from outside the cell.

Receptor

protein that detects a signal molecule and performs an action in response

When a ligand binds to a receptor

The receptor undergoes a conformational change and activates

Receptors can be in the

Plasma membrane or intracellular fluid

Plasma membrane receptors

Large, polar, hydrophilic(most common in signaling pathways)

Intracellular receptors

small or nonpolar ligands can diffuse across the cell membrane

Intracellular receptor examples

Steroid/Hormone nuclear receptors

Gases

Example in intracellular receptors

Plasma membrane receptor examples

G protein, ligand gated ion channels

Transduction

The conversion Of an extra cellular signal to intracellular, signaling that will bring about a cellular response

What does transduction require.

a sequence of changes in a series of molecules known as a signal transduction pathway

How does the signal transduction pathway regulate protein

Phosphorylation by enzyme kinase

Depphosphorylation by phosphatase (shuts off pathways)

Relay signal inside cell

When is the signal amplified

Transduction

Second messengers

Small, non-protein water soluble molecules or ions that send messages throughout the cells by diffusion and amplify the response

What is the most common second messenger

cyclic AMP (cAMP)

Response

The final molecule in the signaling pathway will convert the signal to a response they will alter a cellular response.

Signal transduction pathways can influence

How a cell responses to its environment

How can signal transduction pathways change a cell

Change in gene expression and cell function which can alter phenotypes

What will changes in the signal transduction pathways lead to

Mutations to receptor proteins or to any component of the signaling pathways

What are the two main categories of cell membrane receptors (eukaryotes)

G protein coupled receptors (GPCRs) and Ion channels

GPCRs

Largest categories of cell surface receptors

Important for animal sensory systems

Binds to G protein that binds to GTP

GTP

energy molecules similar to ATP

Ligand binding causes...

Cytoplasmic side to change shape, allowing G protein to bind to GPCR and G protein GDP becomes GTP

When part of the activated G protein binds to the enzyme..

It activates the enzyme and amplifies the signal and leads to a cellular response

What are ion channels important in

Nervous system

Ligand gated ion channels

Receptors that act as a gate for ions

ligand hated ion channel acts..

When ligand binds to receptor, gate opens or closes allowing for the diffusion of specific ions (leads to cellular response )

Binding between ligand and receptor is

highly specific