Lec 2 Cell Communication

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What is a G protein-coupled receptor

a type of cell-surface receptor that works with the help of a G protein

What happens when platelets in the blood encounter damaged tissue

The platelets release PDGF which bind to a receptor kinase which is located on the surface of cells at the site of the wound

What are signaling cells

The source of the signaling molecule

What is the ligand binding site

The specific part of the receptor protein where the signaling molecule binds to

What is binding affinity

The strength of a receptor to bind to a ligand, which as time passes, the ligand is loose than releases

Why does it take a series of protein kinase to activate one after the other until it reaches the nucleus

By phosphorylating each consecutive protein kinase, the signaling molecule causes a larger response

What is the transmembrane domain of a cell surface receptor

The part of the receptor protein that's inside the membrane

What is the signal transduction pathway in cell signaling

A chain reaction of events after the receptor protein is activated by the signaling molecule

What is the signaling molecule

A molecule in which carries information from one cell to another by binding to a receptor protein or a responding cell

What is a receptor kinases

A type of cell-surface receptor which is also an enzyme that adds a phosphate group to another molecule

What is a growth factor

A type of signaling molecule that causes the responding cell to grow or divide

What is a Ras G protein

An intracellular signaling protein which activates (replaces GDP to GTP) when it binds to a receptor kinase.

What is the ligand

Another name for a signaling molecule

How can one signaling molecule have different effects on different types of cells

Because a cell's response to a signaling molecule depends on the different proteins inside the cell

What receptor protein does adrenaline bind to

G protein-coupled receptor

What are the 3 types of cell-surface receptors

G protein-coupled receptors, receptor kinases, ion channels

What type of signaling molecule exists in paracrine signaling

Growth factor

What is the cytoplasmic domain of the cell surface receptor

The part of the receptor protein that's located in the intracellular space

What is the location of a receptor proteins largely dependent on

If the signaling molecule its receiving is polar or nonpolar

What happens when the alpha subunit of a G protein binds to a GTP and separates from the other subunits

In most cases it becomes active and binds to a target protein in the cell

Where are the receptor proteins for nonpolar signaling molecules located

In the cytosol of the responding cell

What are voltage-gated ion channels

Ion channels that open due to the change in voltage in the plasma membrane

What are ligand-gated ion channels

Ion channels that open when they bind to a signaling molecule

What happens when G protein-coupled receptors bind to a G protein

It activates G protein because it allows it to release GTP which it binds to.

What does Ras G protein do once it's activates

It activates a protein kinase in a series of protein kinases referred to as MAP. This series of activating the next protein kinase stops with the final one which enters the nucleus and targets transcription factors

What does the cAMP do (In the case of adrenaline)

It activates protein kinase A (PKA) which phosphorylates proteins in the heart muscle, increasing heart rate

What is the structure of receptor kinases

It contains an extracellular portion which binds to the signaling molecule and an intracellular portion which is the kinase enzyme that transfers a phosphate group to another molecule

What is the α (alpha) subunit of a G protein

The part of the G protein that's initially bound to GDP but replaces with GTP when a ligand binds to the receptor. When bounded to GTP, the subunit separates from the other subunits

At what state is the G protein when it binds to GDP

It's off (inactive)

At what state is the G protein when it binds to GTP

It's on (active)

Where are the receptor proteins for polar signaling molecules (like growth factors) located

On the outside surface of the responding cell

What are the steps of cell signaling

Receptor activation, signal transduction, response, and termination

What happens with receptor kinases activates

Phosphate groups bind to it at multiple sites, which allows further bonding of intracellular signaling proteins

What are the 3 characteristics all G protein-coupled receptors have in common

Share similar structure: single polypeptide chain, ligand-binding site is on the cell surface, and part that binds to G protein is inside the cell All bind with a G protein after being activated The response caused by the receptors are fast and short

What is the second messenger

Signaling molecules inside the cell that carry information to the next target in the signal transduction pathway

What is endocrine signaling

Signaling molecules that travel through the bloodstream

What is autocrine signaling

Signaling molecules that travel to the receptor proteins of the same cell

What happens when adrenaline binds to the G protein-coupled receptor

The G protein replaces the GDP nucleotide with the GTP nucleotide, activating the G protein

What is phosphorylation

The addition of a phosphate group to a protein by a receptor kinases. This results in an active protein which can change shape to bind with other proteins

What happens when the alpha subunit of G protein binds to adenylyl cyclase

The adenylyl cyclase becomes activated and converts the ATP into cAMP which acts as a second messenger

What happens (in the case of adrenaline) when the alpha subunit of the G protein separates from the other subunits

The alpha subunit binds to adenylyl cyclase, located at the cell membrane

What is the extracellular domain of a cell-surface receptor

The part of the receptor protein that binds to the polar signaling molecule and is located in the extracellular space

What do signaling molecules rely on when they have to travel a long way to bond to a responding cell

The bloodstream (circulatory system)

What happens when adrenaline releases from the G protein-coupled receptor

The g protein-coupled receptor inactivates, the g protein inactivates by turning GTP into GDP, cAMP is degraded by enzymes preventing PKA to occur

What is the receptor protein

The molecule on the responding cell that connects to the incoming signaling molecule

What common proteins can receptor proteins be

They can be enzyme or channels

How diverse are G protein-coupled receptors

They're found in almost every eukaryotic organism and consist of a large family

What is the response step of cell signaling

Whatever the cell does as a result of receiving a signal (ex. activate enzymes, change shape)

What is dephosphorylation?

When a phosphate is removed from an active protein by a phosphatase enzyme, turning it into an inactive protein

What is receptor activation in cell signaling

When a receptor protein physically changes when a signal molecule binds to it

What is contact-dependent signaling

When a signaling cell directly makes contact with a responding cell. The signaling molecule travels between the membrane of the two cells and is not released into the extracellular space

What is the termination step of cell signaling

When the cellular response is stopped to prevent the cell from overreacting

What does it mean when receptor kinases dimerizes

When the two pair of protein kinases pair up, holding the signaling molecule in place, activating the receptor

What are the four basic elements involved in cellular communication

signaling cell, signaling molecule, receptor protein, and responding cell

What is paracrine signaling

signaling molecules that travel a short distance using diffusion (20 cells apart)

What is the responding cell

the cell that receives information from the signaling molecule

What are the three subunits some G proteins are composed of

α (alpha), β (beta), and γ (gamma)


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