Cell communication and signalling

Question 1

Cell signalling

Answer 1

Cell communication that governs activity and coordinates cell function and interaction between cells.

Question 2

What can cells do with signalling?

Answer 2

Cells can send signals to other cells and interpret signals from other cells and the environment

Question 3

Signal transduction pathways

Answer 3

A series of steps by which a signal on the cell’s surface is converted to a specific cellular response.

Question 4

Local signalling

Answer 4

between cells in direct contact

Question 5

Cell Junctions

Answer 5

Molecules pass between cells without crossing the plasma membrane

Question 6

Local regulators

Answer 6

Molecules travel short distances between cells

Question 7

Long-distance signaling

Answer 7

Molecules travel longer distances
plants and animals use hormones
Specialized cells release hormones which travel via circulatory system
Only cells with the receptor specific to that signal respond to the signal

Question 8

The three stages of cell signalling

Answer 8

1) Reception
2)Transduction
3)Response

Question 9

Reception: A signal molecule binds to a receptor protein

Answer 9

Most receptor proteins are plasma membrane proteins
The signal molecule is referred to as a ligand

Question 10

Ligand

Answer 10

A molecule that specifically binds to another molecule, often a larger one

Question 11

Receptors

Answer 11

*Most water-soluble ligands bind to specific sites on receptor proteins in the plasma membrane
*Small hydrophobic ligands bind to intracellular receptor proteins found in the cytoplasm or nucleus of target cells

Question 12

The main types of receptor proteins

Answer 12

G protein-coupled receptors-works with G protein –G for-guanine nucleotide (GDP/GTP)
*Receptor tyrosine kinases-proteins with tyrosine kinases in cytoplasm-P from ATP → tyrosine (AA)
*Ion channel receptors-region that acts as a “gate” for ions

Question 13

G protein-coupled receptors (GPCRs)

Answer 13

The G protein acts as an on/off switch. If GDP binds to the G protein the G protein is inactive. Ligand bonding activates the receptor which binds to the G protein, and the G protein is activated. (GDP is displaced by GTP). The G protein dissociates from the receptor and moves away to bind to an enzyme and change its shape, the enzyme is now activated. The GTp is hydrolysed to GDP, inactivating the G protein which dissociates from the enzyme

Question 14

RTK

Answer 14

Kinase= an enzyme that catalyses the transfer of phosphate groups
Tyrosine kinase catalyses the transfer of a phosphate group from ATP to tyrosine
One RTK complex may activate multiple transduction pathways and cellular responses at once