Cell signalling

Question 1

Why do we need cell signalling

Answer 1

Process information

Self preservation - e.g. spinal reflex arc, fleeing from danger

Voluntary movement

Question 2

What are the two main systems within the body that provide lines of communication

Answer 2

Nerve fibres of the central and peripheral nervous system

Blood vessels of the cardiovascular system

Question 3

Endocrine communication

Answer 3

Hormone travels within blood vessels to act on a distant target cell

Glucagon, insulin, adrenaline

Question 4

Paracrin ecommunciation

Answer 4

Hormone acts on an adjacent cell

NO prolduced in blood vessels

Osteoclast activating factors produced by adjacent osteoblasts

Insulin inhibites glucagon secretion

Question 5

Signalling between membrane attached proteins

Answer 5

Blood borne virus detecting by APC

APC digest pathogen

T cell interacts

Bacterai cell wall components - toil-like receptors on haematopoietic cells

CD4 receptors on T lymphocytes

Question 6

Autocrine signalling

Answer 6

Activated T cell secretes IL2 which binds to IL2 on same cell

Question 7

What are ligands

Answer 7

Thigns that exert their effects through binding to receptors

Question 8

What are ligand-gated ion channel receptors

Answer 8

1. Ligand binds to receptors protein

Conformation change results in opening of pore

Pore allows ions to move in or out

E.G. Nicotinic acetylcholine

Question 9

G coupled protein receptors

Answer 9

Channel protein crosses the cell membrane 7 times

Consists of alpha, beta-gamma and GDP molecule

Ligand binding causes G protien complex (heterotrimeric G protien) to associate with receptor resulting in GDP molecule being phosphorylated to GTP and conformational change happen

Ga disscoaited from Gpy subunit

Ga and Gpy act as second messengars and bind to target protein

When ligand dissociates, Internal GTP hydrolyses gtp TO gdp

Ga and Gpy subunits reassociate and once again available to receptor

Question 10

What are enzymze linked receptors

Answer 10

Only consist of one transmembrane domain which has the ligand binding domain on outside and specialised enzyme on inside

Ligand binds results in receptors clustering

Receptors clustering activates enzyem activity

Enzyme phosphorylates the reecptor

Leads to binding of signalling porteins to cytoplasmic domain

Signalling proteins recruit other signalling porteins adn signal is generated

Signal is terminated when phosphatase dephosphorylates the receptor

Question 11

Intracellular receptors

Answer 11

Steroid homrones are membrane permeable (hydrophobic, liphillic), essentially transcription factors

Type 1 receptors - within cytosolic compartment and are associated with chaperone molecules, once hormone binds to receptors, heat shock protein moelcule dissociate allowing hormone receptor compelx to form homodimer with anotehr identical one. Homodimer binds to DNA

Type 2 receptors - nucleus of cell and already bound to DNA, binding of hormone results in direct transcriptional regulation by activated hormone receptor complex