Cell Signalling

Question 1

Why do cells need to communicate?

Answer 1

• Process information - sensory
• Self-preservation - reflexes
• Voluntary movement
• Homeostasis

Question 2

Which cells secrete glucagon?

Answer 2

α cells of Islet of Langerhans in pancreas

Question 3

In response to what is glucagon secreted and what does it do?

Answer 3

In response to hypoglycaemic features, stimulates glycogenolysis and gluconeogenesis

Question 4

What is endocrine signalling?

Answer 4

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

Question 5

What is paracrine signalling?

Answer 5

Signalling molecules act on an adjacent cell

Question 6

Insulin inhibiting glucagon secretion is an example of what type of signalling?

Answer 6

Paracrine signalling

Question 7

Adrenalin acting on the trachea is an example of what type of signalling?

Answer 7

Endocrine signalling

Question 8

Glucagon and insulin acting on the liver is an example of what type of signalling?

Answer 8

Endocrine signalling

Question 9

Nitric oxide produced by endothelial cells causing vasodilation is an example of what type of signalling?

Answer 9

Paracrine signalling as they act on the nearby smooth muscle cells

Question 10

What is signalling between membrane attached proteins?

Answer 10

Plasma membrane proteins on adjacent cells interacting

Question 11

Hepatitis C detected are recognised by which cells in the bloodstream?

Answer 11

Antigen presenting cells (APC)

Question 12

Osteoclast activating factors produced by adjacent osteoblasts is an example of what type of signalling?

Answer 12

Paracrine signalling

Question 13

What happens after APC recognised the pathogen?

Answer 13

APC expressing major histo-compatibility (MHC) class II molecules on surface after digesting the pathogen

Question 14

MHC II interacts with what to alert the lymphocytes?

Answer 14

T-cell receptor (TCR)

Question 15

What type of signalling occurs between APC and T-lymphocyte?

Answer 15

Signalling between membrane attached proteins - Class II MHC and TCR

Question 16

Interaction of HIV GP120 with CD4 receptors of T cells is an example of what type of signalling?

Answer 16

Signalling between membrane attached proteins

Question 17

Bacterial cell wall components interact with toll-like receptors on haematopoietic cells in what type of signalling?

Answer 17

Signalling between membrane attached proteins

Question 18

What is autocrine signalling?

Answer 18

Signalling molecule acts on same cell

Question 19

What cascade of reactions occur after TCR activation?

Answer 19

Expression of IL-2 receptors → Secretion of IL-2

Question 20

What types of signalling are involved in IL-2 secretion by T cells?

Answer 20

Autocrine and paracrine signalling - IL-2 binds to IL-2 receptors on same cell and adjacent cells

Question 21

What type of signalling is involved in positive and negative self-feedback on neurones?

Answer 21

Autocrine signalling

Question 22

ACh providing positive feedback for the presynaptic neurone is an example of what type of signalling?

Answer 22

Autocrine signalling - ACh binds to presynaptic M2-muscarinic receptors to promote NT secretion

Question 23

Which type of signalling is used by the growth factor TGFβ?

Answer 23

Autocrine signalling as it promotes mitogenesis of the same cell

Question 24

What are the 4 main steps of neurotransmission?

Answer 24

1. Propagation of AP
2. NT release from vesicles
3. Activation of postsynaptic receptors
4. Disposal or recollection of NT

Question 25

What are the 4 main types of receptors?

Answer 25

* Ionotropic * G-protein coupled * Enzyme-linked * Intracellular

Question 26

Identify the activation and function mechanisms of G-protein coupled receptors?

Answer 26

Ligand binding → activates intracellular G-protein

Question 27

Identify the activation and function mechanisms of ionotropic receptors?

Answer 27

Ligand binding → opens ion permeable pore traversing the membrane

Question 28

Identify the activation and function mechanisms of enzyme-linked receptors?

Answer 28

Ligand binding → receptor clustering → activates internal enzymes

Question 29

Identify the activation mechanism of intracellular receptors?

Answer 29

A membrane permeable ligand binds to receptor inside cell

Question 30

What type of receptor is Nicotinic ACh receptor?

Answer 30

Ionotropic

Question 31

What is the activator ligand, location and physiological effect of Nicotinic ACh receptor?

Answer 31

Ligand: ACh Location: Skeletal muscle Physiological effect: Muscle contraction

Question 32

What is the action mechanism of GPCR?

Answer 32

GPCR activated by ligand binding → changes conformation of receptor binding to G protein → GTP replaces GDP binding to G protein → G protein dissociates into α and βγ subunits → Gα:GTP complex acts on the target protein → GTP dephosphorylated forcing Gα to couple back with Gβγ

Question 33

What are the components of heterotrimeric G protein?

Answer 33

α, β and γ subunits

Question 34

Why is the protein Gs named that way?

Answer 34

(s)timulates adenylyl cyclase

Question 35

Why is the protein Gi named that way?

Answer 35

(i)nhibits adenylyl cyclase

Question 36

What happens when adenylyl cyclase is stimulated?

Answer 36

converts ATP to cAMP → cAMP activates protein kinase A (PKA)

Question 37

What happens when adenylyl cyclase is inhibited?

Answer 37

PKA level reduced

Question 38

What is an example of GPCR activating Gs?

Answer 38

β1-adrenergic receptor

Question 39

What is an example of GPCR activating Gi?

Answer 39

M2-muscarinic receptor

Question 40

Which protein does Gq act on?

Answer 40

stimulates phospholipase C (PLC)

Question 41

What happens when PLC is stimulated?

Answer 41

Converts PIP2 to IP3 and DAG → IP3 stimulates Ca2+ release and DAG activates PKC

Question 42

Which type of G protein couples with AT-1 (angiotensin) receptor?

Answer 42

Gq protein

Question 43

Which ligand binds and activates the CD220 receptor?

Answer 43

Insulin - resulting in glucose uptake by the cell

Question 44

What type of receptor is CD220?

Answer 44

Enzyme-linked receptor

Question 45

Which ligands bind to the ErbB receptor?

Answer 45

Epidermal growth factor and Transforming growth factor β

Question 46

What is the physiological effect of ErbB when ligand is present?

Answer 46

Cell growth, proliferation

Question 47

What are the 2 types of intracellular receptors?

Answer 47

Type 1 - Cytoplasmic Type 2 - Nuclear

Question 48

Which type of intracellular receptors is associated with heat shock proteins (chaperone molecules, hsp)?

Answer 48

Type 1 - Cytoplasmic

Question 49

What is the action mechanism of cytoplasmic intracellular receptors?

Answer 49

hormone binds to receptor → hsp dissociates → 2 hormone bound receptors form a homodimer → The homodimer translocates to the nucleus binding to DNA

Question 50

What is the action mechanism of nuclear intracellular receptors?

Answer 50

hormone binds to receptor → transcriptional regulation

Question 51

What type of receptor is glucocorticoid receptor?

Answer 51

Type 1 intracellular receptor

Question 52

Which ligands bind to glucocorticoid receptor?

Answer 52

Cortisol and Corticosterone

Question 53

What are the physiological effects of active glucocorticoid receptors?

Answer 53

Reduced immune response and increased gluconeogenesis

Question 54

What type of receptor is thyroid hormone receptor?

Answer 54

Type 2 intracellular receptor

Question 55

Which ligands bind to thyroid hormone receptor?

Answer 55

T3 (thyroxine) and T4 (triiodothyronine)

Question 56

What are the physiological effects of active thyroid hormone receptors?

Answer 56

Growth and development