AP BIO MODS. 21-22

Signal transduction

the process by which a signal from outside the cell leads to a response inside the cell

Signaling Molecule

binds to a receptor

Receptor activation

the receptor changes its shape, and this conformational change is what activates the receptor

Response

the activated receptor then trigger a pathway that leads to the cells response

Termination

the response is ended a short time after it begins

Receptor Binding

Similar to enzyme specificity, receptor proteins in cell communication must match signaling molecules in molecular shape, structure, and charge distribution in order for the receptor and signal to fit together so that they can bind to one another

Adrenaline

Hormones are released into the blood during emergencies or exercise.

Insulin

A hormone that helps regulate glucose levels in the blood 

When insulin binds to muscle or fat cells it does what?

stimulates an increase in the number of glucose transporters in the cell membranes

When insulin binds to liver cells, the activated receptor triggers what

a pathway that increases the rate at which the cell assembles glycogen from glucose

What are two things adrenaline does?

increases heart rate and widens airways

Hydrophobic signaling

molecules cannot pass through the cell membrane to enter the cell and binds to ligand-binding domains of membrane-bound receptor proteins

Before the extracellular

signal is bound

What  3 groups of receptor proteins bind hydrophilic signaling molecules

G Protein-Coupled Receptors

Receptor-protein kinases

Ligand-gated ion channels

3 unifying factors for :

G Protein-Coupled Receptors

Receptor-protein kinases

Ligand-gated ion channels

1. All signals are water soluble

2. The receptor proteins are located on the target cell’s plasma membrane as embedded proteins

3. Responses by the target cells are rapid and short lived

Amplification

an increase 

G protein-coupled receptor

a type of receptor protein that, when activated, uses a molecule called a G protein as part of the signal transduction pathway where the external signal is the first message to the target cell that it will be changing its activity

second messenger

an intermediate signaling molecule, amplifying the response in the cell

Receptor

a membrane embedded protein that loops back and forth and crosses the cell membrane seven times

Activation

receptor by binding the signal allows the receptor to bind to the G protein

Response (again)

the G protein releases a molecule of GDP and replaces it with GTP, activating it

the active adenylyl cyclase  converts ATP to a derivative called _______, which is the second messenger

cyclic adenosine monophosphate (cAMP)

kinases

an enzyme that, when activated, catalyzes the transfer of phosphate groups from ATP to proteins

Signaling cascade

a small amount of signal is amplified to produce a large cellular response

Signaling cascade

a small amount of signal is amplified to produce a large cellular response

Termination

The signaling pathway begins when adrenaline dissociates from its receptor.  

Phosphatase

an enzyme that removes the phosphate groups from activated kinases so they revert to the inactive state

Ligand-gated channel

a receptor protein including a membrane-spanning channel that opens or closes (is gated) in response to binding a signaling molecule (ligand).

Receptor-protein kinase

a two-in-one/dual function protein having both a signal-binding extracellular domain and a kinase intracellular domain

cytoplasmic-signaling proteins

trigger the rest of the signal transduction pathway that triggers the response of the target cells

The change in shape allows the activated receptor protein to interact with proteins

cytoplasmic-signaling proteins

Acetylcholine

quickly degraded after binding, producing

a short-lived but dramatic response 

Hydrophobic signaling molecules

lipids that do not readily dissolve in water, but are readily soluble in lipids.

Internal receptor proteins, when activated, cause changes in the what? Resulting in turning some genes on and others off

 gene expression

Steroid hormones

are hydrophobic signaling molecules which are lipids derived from the cholesterol molecule.