Bk 2 Ch 4 Cell Communication

Question 1

Signal transduction

Answer 1

The process by which an extracellular signal is communicated or transmitted from the exterior of the cell to inside the cell and converted into a form that can bring about a specific cellular response.

Question 2

Contact dependent signalling

Answer 2

Intercellular communication that depends upon direct contact between surface-bound molecules located on the signalling and the target cell membranes.

Question 3

Paracrine

Answer 3

Mode of intercellular signalling in which a signalling molecule acts locally, on nearby cells. The signalling molecules involved are often cytokines.

Question 4

Cytokine

Answer 4

Small protein molecules commonly used as intercellular signalling molecules by the cells of the immune system. Activation of different types of cytokine receptors results in a wide range of cellular responses such as secretion of other signalling mediators, the promotion of growth, proliferation and movement. There are many different cytokines, many of which act only on specific types of cell.

Question 5

Growth factors

Answer 5

A general term for signalling molecules, usually polypeptides, that bind to cells carrying appropriate receptors and ultimately alter gene expression to stimulate growth, survival or division of the cell.

Question 6

Autocrine signalling

Answer 6

Type of cellular communication in which a cell secretes a signalling molecule that binds to and activates receptors on its own surface. Autocrine signalling enables cells to amplify a positive signal in a controlled manner.

Question 7

Endocrine signalling

Answer 7

Type of intercellular signalling that involves the transport of signalling molecules (hormones), via some sort of transport system, to target cells that can be some distance away from the signalling cell. In vertebrates, such signalling molecules are transported in the vascular system.

Question 8

Hormones

Answer 8

Signalling molecule released from specialised cells and distributed (in the vascular system in vertebrates) to act on target cells at some distance from the site of release.

Question 9

Adrenaline

Answer 9

A hormone (also known as epinephrine) released into the blood supply from the adrenal glands, small glands located above the kidneys in mammals. This hormone is released during periods of acute stress and is responsible for the ‘fight or flight’ response, so called because it readies the body for action in a hazardous situation.

Question 10

Epinephrine

Answer 10

A hormone (also known as adrenalin) released into the blood supply from the adrenal glands, small glands located above the kidneys in mammals. This hormone is released during periods of acute stress and is responsible for the ‘fight or flight’ response, so called because it readies the body for action in a hazardous situation.

Question 11

Neurotransmitter

Answer 11

Chemical signal released by neurons at the synapse in response to the arrival of an action potential. The neurotransmitter binds to receptors on the postsynaptic target cell (which may be another neuron, a muscle cell or an endocrine cell) and elicits a response.

Question 12

Gap junction signalling

Answer 12

A type of specialised cell junction that allows intercellular communication, by passage of ions, small molecules and electrical signals between cells.

Question 13

Electrical signalling via chemical transmission

Answer 13

Signalling cell transmits information in form of changes in membrane potential along the length of the cell; the electrical signal is transferred from the signalling cell to the target cell either in chemical form as a neurotransmitter or fire gap junctions.

Question 14

Guanylate cyclase

Answer 14

Enzyme that catalyses the formation of the second messenger cGMP. It is activated by nitric oxide (NO), and some cell surface receptors have intrinsic guanylate cyclase activity.

Question 15

cyclic GMP (cGMP)

Answer 15

A second messenger produced from GTP by the enzyme guanylate cyclase. Guanylate cyclase is activated by the signalling molecule nitric oxide (NO) and also by a subtype of cell surface receptors that have intrinsic guanylate cyclase activity.

Question 16

Cascade

Answer 16

A sequence of reactions in which a small number of precursor molecules is succeeded by a larger number of product molecules. A cascade reaction may comprise an induced defence response. It consists of about 20 different proteins found in blood and body tissue, which are inactive until cleaved. See also complement system.

Question 17

Adenylate cyclase

Answer 17

Enzyme that catalyses the production of cyclic AMP from ATP. It is activated or inhibited by activated G protein subunits, mostly by different forms of Gα

Question 18

Phospholipase C (PLC)

Answer 18

A lipid-modifying enzyme that, depending on the isoform, is activated upon activation of some G protein-coupled receptors (GPCRs) or of some receptor tyrosine kinases (RTKs). PLC cleaves phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) to release the second messengers inositol 1,4,5-triphosphate (IP3) into the cytosol and 1,2-diacylglycerol (DAG), which remains attached to the inner side of the plasma membrane.

Question 19

Cyclic AMP (cAMP)

Answer 19

A second messenger produced from ATP by the enzyme adenylate cyclase upon activation by the a subunit of activated trimeric G protein receptors. cAMP transduces the signal by binding to and activating protein kinase A, which phosphorylates downstream targets.

Question 20

Protein Kinase A (PKA)

Answer 20

Also known as cAMP-dependent protein kinase; a serine-threonine kinase that is activated by the second messenger cAMP. It has many targets such as enzymes involved in glycogen metabolism and CREB (cyclic AMP response element binding protein).

Downstream proteins phosphorylated by PKA vary according to the type of cell that’s receiving the signal. – Different response in different cell types.

Question 21

AMP

Answer 21

Adenosine monophosphate

Is hydrolysed from camp by camp phosphodiesterases