16 - Cell Signalling 2

Question 1

Types of chemical messengers

Answer 1

• Small hydrophilic molecules
• Small lipophilic (hydrophobic) molecules
• Other small molecules (amino acids, nucleotides, ions, gases)

Question 2

Examples of small hydrophilic molecules

Answer 2

Amines (adrenaline), peptides and proteins (insulin and interleukin). Dissolve easily in aqueous solution.

Question 3

Small lipophilic/hydrophobic molecules

Answer 3

Steroids (cortisol, oestrogen, testosterone). do not dissolve in aqueous solution

Question 4

Signalling receptors

Answer 4

protein which exerts a physiological effect after binding its natural ligand (signalling molecules)

Question 5

Ligand binding

Answer 5

High specificity and high affinity (low ligand concentration)

Question 6

Receptor response after ligand binding

Answer 6

Binding of ligand changes receptor conformation, changing receptors interactions with other molecules

Question 7

2 classes of receptors

Answer 7

Cell surface receptors and nuclear receptors

Question 8

Which type of signalling molecule can pass through the membrane

Answer 8

Lipophilic (fat soluble). Receptor in nucleus or cytosol. Hydrophilic (water soluble) molecules pass signal through membrane (receptor on cell surface)

Question 9

Cell surface receptor

Answer 9

Peptide or amine hormone binds to receptor on the outside of the cell. Acts through receptor without entering the cell

Question 10

Nuclear receptor

Answer 10

Steroid or thyroid hormone enters the cell. Hormone receptor complex acts in the nucleus

Question 11

Nuclear Receptor Structure

Answer 11

• Central DNA binding domain
• Ligand binding domain
• Transactivation domain (variable N terminal domains)

Question 12

Type 1 nuclear receptor activation

Answer 12

Inactive receptor bound to inhibitory proteins (Hsp70) in cytosol. Ligand binds to receptor, inducing a conformational change. Inhibitory protein released and coactivator induces transcription

Question 13

Type 2 nuclear receptor activation

Answer 13

Inactive receptor bound to inhibitory proteins (HRE and corepressor) in nucleus. Ligand binds to receptor, inducing a conformational change. Inhibitory protein released and coactivator induces transcription

Question 14

Where in gene structure is hormone response element found

Answer 14

Regulatory region

Question 15

Nuclear receptor response elements

Answer 15

Adjacent to the genes the hormone (ligand) regulates. Binding is specific despite similarity in base pairs

Question 16

Nuclear receptor response elements structure

Answer 16

6 base pair repeat sequences (sometimes inverted), separated by 3-5 base pairs

Question 17

Is there a limited or unlimited application of signal via nuclear receptor signalling

Answer 17

Limited

Question 18

Example of receptor enzymes

Answer 18

Tyrosine Kinases (catalytic receptors)

Question 19

True or False. Enzymes cause a cascade effect (1 molecule effecting production of 100,000 molecules)

Answer 19

True

Question 20

example of an RTK

Answer 20

insulin receptor which affect many pathways to respond in many ways

Question 21

Insulin receptor

Answer 21

Spans the membrane. Binding causes conformational change. Allows autophosphorylation which activates the tyrosine kinase domain which have intracellular targets

Question 22

rapid effects of RTKs

Answer 22

• Changes to enzymatic activity
• Activate second messengers
• Vesicle translocation to membrane

Question 23

slow effects of RTKs

Answer 23

Regulate gene expression