Hormones & Cell Signalling

Question 1

• What are the three main types of cell communication?

Answer 1

Autocrine, paracrine & endocrine

Question 2

• What are the consequences of cell signalling?

Answer 2

Cells survive, divide, differentiate or die

Question 3

• What are the two types of hormones? And how do they differ?

Answer 3

Lipid soluble – diffuse through plasma membrane, alter expression of genes at the nucleus
Water soluble – bind to receptors on the surface of the cell, initiate intracellular events

Question 4

• What are some examples of lipid soluble hormones and where are they produced?

Answer 4

Adrenal glands – androgens, cortisol, aldosterone, ovaries – estradiol, testes – testosterone

Question 5

• How does a lipid soluble hormone work?

Answer 5

Activates a nuclear receptor which recruits additional co-activator proteins which then regulate the activation and repression of nearby target genes

Question 6

• How does a water soluble hormone function?

Answer 6

Induces intracellular signal transduction pathways e.g. adenyl cyclase (ACTH), guanylyl cyclase (ANP), phospholipase C (GnRH), tyrosine kinase (insulin), ion channels

Question 7

• What are the three components of a membrane receptor?

Answer 7

External domain, transmembrane domain & cytoplasmic/intracellular domain

Question 8

• What are some of the fundamental processes controlled by growth factors & cytokines?

Answer 8

Cell division, cell differentiation, programmed cell death

Question 9

• What are some of the pathways used by growth factors?

Answer 9

Ras/GAP, PI3 kinase, STAT

Question 10

• What two factors does the removal of a signal depend on?

Answer 10

The rate of destruction of molecules that the signal affects and the promptness of response when a signal is turned on

Question 11

• What two factors determine the half-life of a signalling molecule?

Answer 11

Rate of synthesis and the modification of proteins

Question 12

• What are the possible effects of ACh?

Answer 12

Heart muscle cell – decreased rate of force contraction
Salivary gland cell – secretion
Skeletal muscle cell – contraction

Question 13

• What are the main classes of cell surface receptor?

Answer 13

Ion-channel linked, G-protein linked, tyrosine kinase linked, receptors with intrinsic enzymatic activity

Question 14

• What are second messengers?

Answer 14

Small intracellular signalling molecules, amplify the signal e.g. cAMP & Ca2+

Question 15

• What are the functions of intracellular proteins?

Answer 15

Scaffolds, relays, adaptors, amplifiers, modulators

Question 16

• What are the two types of protein phosphorylation?

Answer 16

Serine/threonine residues & tyrosine residues

Question 17

• What is signal transduction?

Answer 17

The adding and removing of phosphate groups – can alter enzyme activity, protein stability & protein interactions

Question 18

• What is a G protein?

Answer 18

Guanine-nucleotide binding protein, a signal transducing protein

Question 19

• What are the stimulatory effects mediated by the adenylate cyclase system?

Answer 19

Subunit of G protein activates adenylate cyclase, ATP converted to cAMP, cAMP activates catalytic subunit of protein kinase A, pKA is part of cascade of intracellular phosphorylations

Question 20

• What is a key feature of the adenylate cyclase system?

Answer 20

Signal amplification

Question 21

• What are the two types of enzyme linked receptors?

Answer 21

Function directly as enzymes or directly associated with enzymes they activate

Question 22

• What is an example of a tyrosine kinase linked receptor?

Answer 22

Insulin and IGF-I receptors

Question 23

• How does a tyrosine kinase receptor initiate a response?

Answer 23

Phosphorylation of the receptors intracellular domains create docking surfaces for other cell signalling proteins

Question 24

• What are the six classes of enzyme linked receptors?

Answer 24

Receptor tyrosine kinases, tyrosine kinase associated receptors, receptor like tyrosine phosphatases, receptor serine/threonine kinases, receptor guanyl cyclases, histidine kinase associated receptors

Question 25

• What are the two main classes of molecular switch?

Answer 25

Phosphorylation & GTP binding

Question 26

• How might a cell alter sensitivity to a signal?

Answer 26

Receptor sequestration, receptor down regulation, receptor inactivation, inactivation of signalling protein, production of inhibitory protein