Cell Communication

Question 1

What is cell signaling and why is it important?

Answer 1

Cell signaling is a communication process that governs basic activities of cells and coordinates all cell actions.

It is important because the ability of cells to perceive and correctly respond to their microenvironment is the basis of development, tissue repair, and immunity, as well as normal tissue homeostasis.

Errors in signaling interactions and cellular information processing are responsible for diseases such as cancer, autoimmunity, and diabetes. By understanding cell signaling, diseases may be treated more effectively.

Question 2

What is phosphorylation?

Answer 2

Phosphorylation plays a role in the transmission of intracellular signals.

In protein phosphorylation, a phosphate group (PO4-3) is added to residues of the amino acids serine, threonine, and tyrosine. This is possible because they contain a hydroxyl group.

Question 3

What are second messengers?

Answer 3

Second messengers may play a role in signal transmission.

Cyclic AMP (cAMP) serves as a second messenger to activate or inactivate proteins within the cell.

Termination of the signal occurs when an enzyme called phosphodiesterase converts cAMP into AMP.

Question 4

What is phospholipase C?

Answer 4

The enzyme phospholipase C breaks down PIP2 into IP3 and DAG, both of which serve as second messengers.

Question 5

What are autoinducers?

Answer 5

Small molecules or proteins produced by bacteria that regulate gene expression. When cell density is low, they diffuse away,

Question 6

Describe the process of cell signaling

Answer 6

Hydrophobic signaling molecules diffuse across the plasma membrane and interact with intracellular receptors in the cytoplasm. Many intracellular receptors are transcription factors that interact with DNA in the nucleus and regulate gene expression.

Question 7

Binding of a ligand initiates

Answer 7

Signal transduction

Question 8

Synaptic gap

Answer 8

The distance between the presynaptic cell and the postsynaptic cell is very small and allows for rapid diffusion of the neurotransmitter

Question 9

What are some responses to cell signals?

Answer 9

-gene expression
-cell death
-cell growth
-termination of the signal cascade

Question 10

Autocrine signaling

Answer 10

A cell targets itself

Question 11

Paracrine signaling

Answer 11

A cell targets a nearby cell

Question 12

Endocrine signaling

Answer 12

A cell targets a distant cell through the bloodstream

Question 13

Signaling across gap junctions

Answer 13

A cell targets another cell connected by gap junctions

Question 14

What is the process of cell signaling as it occurs in neurotransmitters?

Answer 14

The distance between the presynaptic cell and the postsynaptic cell—called the synaptic gap—is very small and allows for rapid diffusion of the neurotransmitter. Enzymes in the synaptic cleft degrade some types of neurotransmitters to terminate the signal.

Question 15

How does cell signaling occur with ion channels?

Answer 15

Gated ion channels form a pore through the plasma membrane that opens when the signaling molecule binds. The open pore then allows ions to flow into or out of the cell.

Question 15

What is the process of cell signaling as it occurs with receptor tyrosine kinase?

Answer 15

The signaling molecule binds to the receptor tyrosine kinase, and the receptors dimerize. Tyrosine residues are phosphorylated, leading to a downstream cellular response.

Question 16

What is an example of cell signaling as it occurs with hormones?

Answer 16

Steroid hormones have similar chemical
structures to their precursor, cholesterol.
Because these molecules are small and
hydrophobic, they can diffuse directly
across the plasma membrane into the
cell, where they interact with internal
receptors.

Question 17

Signaling in bacteria

Answer 17

Some species of bacteria that use quorum sensing form biofilms, complex colonies of bacteria (often containing several species) that exchange chemical signals to coordinate the release of toxins that will attack the host.

Question 18

ERK is a ______________ that activates translation when phosphorylated.

Answer 18

map kinase

Question 19

How is EGF an example of a receptor tyrosine kinase?

Answer 19

The epidermal growth factor (EGF) receptor (EGFR) is a receptor tyrosine kinase involved in the regulation of cell growth, wound healing, and tissue repair.

When EGF binds to the EGFR, a cascade of downstream events causes the cell to grow and divide. If EGFR is activated at inappropriate times, uncontrolled cell growth (cancer) may occur

Question 20

What type of molecule acts as a signaling molecule in yeasts?

Answer 20

Mating factor

Question 21

What property prevents the ligands of cell-surface receptors from entering the cell?

Answer 21

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