Cell Communication

Place the following steps of a signal transduction pathway in order. The receptor activates a protein at the membrane Final Target Causes response A ligand binds to the cell-surface receptor Second messenger molecules are released.

1. A ligand bind to the cell-surface receptor 2. The receptor activates a protein at the membrane 3. Second messenger molecules are released 4. Final target causes a response.

How many transmembrane domains do G-Protein linked receptors have?

7

What is a dimer?

A chemical compound formed when two molecules which are often identical join together

What is a synaptic signal?

A chemical signal that travels between nerve cells

What is autocrine signaling?

A form of cell signaling in which a cell secretes a ligand that binds to autocrine receptors on that same cell, leading to changes in the cell

What is a ligand?

A molecule that binds to another specific molecule, delivering a signal

What is an internal receptor?

A receptor that responds to hydrophobic ligand molecules that are able to travel across the plasma membrane

The amino acids on the inside of the membrane of an Ion channel linked receptor are A. Hydrophilic B. Hydrophobic C. Amphipathic D. Amphiphobic

A. Hydrophilic

Which of the following statements is true of ligands? A. The binding of a ligand to a receptor molecule causes the receptor to change shape B. All Ligands are proteins C. Each ligand is only able to bind to one specific receptor D. Ligands can bind to cell-surface receptors, but they cannot enter the cell

A. The binding of a ligand to a receptor molecules cause the receptor to change shape

A cell releases chemical signals into its surrounding space in order to communicate with neighboring cells. Which of the following must occur for the communication to be successful. A. The neighboring cell must have the right receptor to receive the signal B. The same chemical signal must be produced within the neighboring cells C. The chemical signal must bind to hormones on the neighboring cells D. The neighboring cells must be able to absorb the chemical through diffusion

A. The neighboring cell must have the right receptor to receive the signal.

Endocrine signals are transmitted more slowly than paracrine signals because ________ A. the ligands are transported through the bloodstream and travel greater distances B. the target and signaling cells are close together C. the ligands are degraded rapidly D. the ligands don't bind to carrier proteins during transport

A. the ligands are transported through the bloodstream and travel greater distances

Cyclic AMP is synthesized from what?

ATP

Which enzyme turns ATP into cAMP?

Adenylyl cyclase

What are the three main components of a cell surface receptor?

An external ligand-binding domain (the extracellular domain) A hydrophobic membrane spanning region Intracellular domain inside the cell

What is signal transduction?

An extracellular signal is converted into an intercellular signal

All G-protein linked receptors have how many transmembrane domains? A. 2 B. 7 C. 10 D. 8

B. 7

What is the function of a phosphatase? A. A phosphatase removes phosphorylated amino acids from proteins. B. A phosphatase removes the phosphate group from phosphorylated amino acid residues in a protein. C. A phosphatase phosphorylates serine, threonine, and tyrosine residues. D. A phosphatase degrades second messengers in the cell.

B. A phosphatase removes the phosphate group from phosphorylated amino acid residues in a protein

Which of the following has GTPase activity? A. G-protein coupled receptor B. G-protein C. Adenylyl Cyclase D. cAMP-dependent protein kinase E. Phosphatases

B. G-protein

The amino acids on the outside of the membrane of an Ion channel linked receptor are: A. Hydrophilic B. Hydrophobic C. Amphipathic D. Amphiphobic

B. Hydrophobic

Why are ion channels necessary to transport ions into or out of a cell? A. Ions are too large to diffuse through the membrane B. Ions are charged particles and cannot diffuse through the hydrophobic interior of the membrane C. Ions do not need ion channels to move through the membrane D. Ions binds to carrier proteins in the bloodstream, which must be removed before transport into the cell

B. Ions are charged particles and cannot diffuse through the hydrophobic interior of the membrane

Which of the following statements regarding cell signaling is true? A. Direct signaling is a type of signaling found only in plant cells B. Paracrine signaling allows neighboring cells to communicate over relatively short distances C. Synaptic signaling is a type of autocrine signaling D. In endocrine signaling, signals are released from a cell and bind to receptors on its own cell membrane

B. Paracrine signals allows neighboring cells to communicate over relatively short distances

Autophosphorylation involves A. The spontaneous phosphorylation of a protein B. Phosphorylation of a kinase by itself or other like kinases C. The spontaneous and non-specific phosphorylation of proteins D. The spontaneous and non-specific phosphorylation of proteins E. Phosphorylation of phosphate groups

B. Phosphorylation of a kinase by itself or other like kinases

What property prevents the ligands of cell-surface receptors from entering the cell? A. The molecules bind to the extracellular domain B. The molecules are hydrophilic and cannot penetrate the hydrophobic interior of the plasma membrane C. The molecules are attached to transport proteins that deliver them through the bloodstream to target cells D. The ligands are able to penetrate the membrane and directly influence gene expression upon receptor binding

B. The molecules are hydrophilic and cannot penetrate the hydrophobic interior of the plasma membrane

How do paracrine signals move?

By diffusion through the extracellular matrix

What is the effect of an inhibitor binding an enzyme? A. The enzyme is degraded B. The enzyme is activated C. The enzyme is inactivated D. The complex is transported out of the cell

C. The enzyme is inactivated

When a ligand binds to the extracellular region of an Ion channel: A. A signal is immediately propagated B. The cell reestablishes a concentration gradient of ions and prepares to release another signal C. There is a conformational change in the protein's structure that allows ions to pass through D. Ions can immediately diffuse into the cell without disturbing the shape of the protein

C. There is a conformational change in the protein's structure that allows ions to pass through

What property enables the residues of the amino acids serine, threonine, and tyrosine to be phosphorylated? A. They are polar. B. They are non-polar. C. They contain a hydroxyl group. D. They occur more frequently in the amino acid sequence of signaling proteins.

C. They contain a hydroxyl group

The secretion of hormones by the pituitary gland is an example of ______________. A. autocrine signaling B. Paracrine signaling C. endocrine signaling D. Direct signaling across gap junctions

C. endocrine signaling

Name a widely used second messenger.

Calcium

What are the four types of second messenger?

Calcium IP3 DAG cAMP

Signal transduction pathways only occur with what type of receptors?

Cell Surface Receptors

Signal transduction only occurs with what kind of receptors?

Cell Surface receptors

What is a cell surface receptor?

Cell surface, membrane anchored (integral proteins) that bind to external ligand molecules

What is a target cell?

Cells that are affected by chemical signals (also called receptors)

Define intercellular signaling.

Communication between cells

Define intracellular signaling.

Communication within a cell

Apoptosis can occur in the cell when the cell is ________. A. Damaged B. No longer needed C. Infected with a virus D. All of the Above

D. All of the above

Where do DAG and IP3 originate? A. They are formed by phosphorylation of cAMP. B. They are ligands expressed by signaling cells. C. They are hormones that diffuse through the plasma membrane to stimulate protein production. D. They are the cleavage products of the inositol phospholipid, PIP2.

D. They are the cleavage products of the inositol phospholipid, PIP2

How do you terminate a signal cascade?

Degrade the ligand or remove it so that it can no longer access its receptor

Which of the following transduce an extracellular signal into an intracellular signal? A. ligand-gated ion channels B. Steroid receptors C. G-protein coupled receptors D. A & C E. A, B & C

E. A, B & C

Which of the following are considered second messengers? A. Ca2+ B. IP3 C. DAG D. A & B E. A, B& C

E. A, B &, C

Which of the following is true regarding cell receptors? Choose all that apply. A. Ligand-gated ion receptors form a group of signaling molecules called growth factors B. Intracellular receptors can be found in the cytoplasm or nucleus C. G Protein-coupled receptors (GPCRs) are the most diverse type of cell receptor D. A, B & C E. B & C

E. B & C

What is apoptosis? A. A mechanism for inducing cellular differentiation B. A checkpoint within the cell cycle C. The replication of mitochondria D. The replication of chloroplasts E. Programmed cell death

E. Programmed cell death

The alpha subunits of G-protein receptors hydrolyze what in to what?

GTP into GDP

What do many internal receptors influence?

Gene expression

Are paracrine signaling molecules present in high or low concentration when they act on their target cells?

High

Ligands released by endocrine signaling are called what?

Hormones

For signaling purposes, calcium is stored where?

In cytoplasmic vesicles (Endoplasmic Reticulum)

Where are internal receptors found?

In the cytoplasm of the cell

What is an enzyme linked receptor?

Intracellular domains that are associated with an enzyme

The small signaling molecules that diffuse between two cells in direct signaling across gap junctions or plasmodesmata are called?

Intracellular mediators

What are the three general categories of cell surface receptors?

Ion channel linked G Protein linked Enzyme

The transfer of a phosphate is catalyzed by what enzyme?

Kinase

What kind of molecules cannot fit through the water-filled channels in gap junction signaling?

Large molecules

Are hormones present in high or low concentrations when they act on their target cells?

Low

Ions flowing into a cell changes the cell's what?

Membrane potential

Calcium triggers __________ ____________.

Muscle contractions

Do ligands that interact with Cell Surface receptors have to enter the cell in order to elicit a response?

No.

Autocrine signaling regulates what two things?

Pain sensation and Inflammatory responses

What are the five categories of signaling?

Paracrine Endocrine Autocrine Direct Signaling across Gap Junctions Synaptic

How are paracrine signaling responses kept localized?

Paracrine ligand molecules are quickly degraded by enzymes or removed by neighboring cells to reestablish the concentration gradient for the signal.

What is a receptor?

Protein molecules in the target cell or on the cell surface that bind to a ligand

Paracrine signals usually elicit ________ responses that last a __________ amount of time.

Quick Short

Which amino acids become phosphorylated?

Serine, Threonine, Tyrosine

Cell surface receptors are key in initiating what kinds of pathways?

Signal transduction

Define direct signaling across Gap Junctions.

Signaling through cell-cell contact. Gap junctions in animals and plasmodesmata in plants are tiny channels that directly connect neighboring cells. These water-filled channels allow small signaling molecules, called intracellular mediators, to diffuse between the two cells.

What is endocrine signaling?

Signals from distant cells that originate from endocrine cells (thyroid gland, hypothalamus, pituitary gland)

What is signal integration?

Signals from two or more different CSRs merge to activate the same response in the cell

What is paracrine signaling?

Signals that act locally between cells that are close together

Endocrine signals usually produce a __________ response but have a __________ lasting effect.

Slower Longer

Which type of ligand can directly diffuse through the plasma membrane and interact with internal receptors?

Small hydrophobic ligands

What are the two main types of ligands?

Small hydrophobic ligands Water soluble ligands

What are second messengers?

Small molecules that propagate a signal after it has been initiated by the binding of the signaling molecule to the receptor

What is a second messenger?

Small molecules that propagate a signal after it has been initiated by the binding of the signaling molecule to the receptor

What is the most important type of small, hydrophobic ligand?

Steroid hormones

Ligands interact with proteins in ________ _________.

Target cells

What happens after a G-Protein is activated?

The G-protein interacts with either an ion channel or an enzyme in the membrane.

Place the following steps of G-Protein linked receptors in order: The subunits of the G protein split into the alpha subunit and the Beta Y subunit The Gamma subunit Binds to the receptor and the resultant shape change activates the G-Protein which Releases GDP and picks up GTP The GTP on the active alpha subunit is hydrolyzed to GDP and the Beta Y subunit is deactivated

The Gamma subunit Binds to the receptor and the resultant shape change activates the G-Protein which Releases GDP and picks up GTP The subunits of the G protein split into the alpha subunit and the Beta Y subunit The GTP on the active alpha subunit is hydrolyzed to GDP and the Beta Y subunit is deactivated

What is phosphorylation?

The addition of a phosphate group to a molecule

What is the main difference between the categories of cell signaling?

The distance that the signal travels

How do second messengers help spreading a signal?

They alter the behavior of certain cellular proteins

How do G-Protein linked receptors elicit a response?

They bind to a ligand and activate a membrane protein called a G-Protein.

How do Ion Channel linked receptors elicit a response?

They bind to a ligand and open a channel through the membrane that allows specific ions to pass through.

What do many internal receptor ligands do once inside of cells?

They bind to proteins that act as regulators of mRNA transcription to mediate gene expression.

What is the main role of Cyclic AMP in cells?

To bind to and activate an enzyme called cAMP-dependent kinase and phosphorylates serine and threonine.

What is Nitric oxide's role as a ligand?

To interact with receptors in smooth muscle and induce relaxation of the tissue

What is one example of paracrine signaling?

Transfer of signals across synapses between nerve cells

What is the function of a tyrosine kinase receptor?

Transfers phosphate groups to tyrosine molecules

What type of amino acid autophosphorylates?

Tyrosine

What is an example of an enzyme linked receptor?

Tyrosine Kinase receptor

Which ligands are sometimes to large to move into the cell?

Water-soluble ligands

Which ligands bind to the Extracellular domain of the cell surface receptors?

Water-soluble ligands

Which type of ligands are polar and cannot pass through the plasma membrane unaided?

Water-soluble ligands

What is signal amplification? Which type of receptor most accurately represents this?

Where one signaling molecule can elicit many responses G-Protein linked Receptors

G-protein linked receptors occur as a ____________ series of events.

cyclic

Hormones travel ________ distances between endocrine cells and target cells through the ____________.

long bloodstream