Cell signalling

Question 1

What is the purpose of cell communication?

Answer 1

Homeostasis
Self preservation
Processing information
Voluntary movement

Question 2

What is endocrine communication?

Answer 2

Endocrine glands consider the direct secretion and release of hormones int the blood

Question 3

What is the process of glucagon secretion?

Answer 3

Glucagon is secreted by alpha-cells of islets of Langerhans
Traverses out of the pancreas and released into blood vessels
Binds to glucagon receptor (G-coupled receptor)
Secondary messenger system to increase hepatic glucose output

Question 4

What type of receptor are glucagon receptors?

Answer 4

G-coupled receptors

Question 5

What are the examples of endocrine communciation?

Answer 5

Hormones travel within vasculature to bind onto distant target cell receptors
Insulin (Produced in pancreas, acts on muscle, liver and adipose)
Adrenaline produced by adrenal medulla

Question 6

Describe the paracrine communication involved in hyperglycemia:

Answer 6

Insulin secretion by B-cells in the islets of Langerhans

Inhibits glucagon secretion

Question 7

What is paracrine signalling?

Answer 7

Hormones act on adjacent cell

Question 8

What are the examples of paracrine communication?

Answer 8

Osteoclast activating factor produced by adjacent osteoblasts
Nitric oxide (mediates vasodilation) produced by endothelial cells

Question 9

How do antigen presenting cells present antigens?

Answer 9

Antigens undergo internalization and fragmentation and the endoplasmic reticulum, proteases cleave antigen into antigenic fragments, associated to MHC molecules on cell surface membranes

Question 10

What receptors bind to MHC Class 2 molecules?

Answer 10

TCRs

Question 11

The interaction between T-cell receptors and MHC-II is an example of what?

Answer 11

Signalling between membrane attached proteins

Question 12

What is autocrine signaling?

Answer 12

Communication with self

Question 13

What is the examples exhibited by T-cells during autocrine cell signaling?

Answer 13

Secretion of IL-2 from activated T-Cell
Binds onto cell surface membrane receptor
IL-2 promotes differentiation into T-effector and memory cells

Question 14

What are ionotropic receptors?

Answer 14

Ligand binding –> opens ion permeable pore traversing the membrane

Question 15

What is the structure of ionotropic receptors?

Answer 15

Transmembrane protein consists of a central pore within quaternary structure: Ligand-binding domain results in pore opening

Question 16

Describe the sequence events upon ligand binding on ionotropic receptors?

Answer 16

Ligand binds onto receptor protein
Change in conformation of channel proteins –> Opening of a pore
Pore facilitates the movement of ions according to concentration gradient

Question 17

What are the examples of ionotropic receptors?

Answer 17

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

Question 18

What are the sequence events following binding of G-protein coupled receptor?

Answer 18

7-TM receptor & heterotrimeric G-protein are inactive
Ligand binding –> conformational change of receptor
Unassociated g-protein binds to the receptor –> Bound GDP molecule is phosphorylated to GTP
G-protein dissociates into two components (Alpha, and g-beta/gamma)
Binding to target proteins

Internal GTPase activity on alpha subunit dephosphorylates GTP to GDP
Heretrotimeric G dissociates upon ligand deactiviation

Question 19

What are the two components in which G-protein splits into?

Answer 19

Alpha subunit

Beta & Gamma subunits

Question 20

What is associated with the alpha subunit?

Answer 20

GTP and GTPase –> GDP

Question 21

What is the name for the transmembrane protein involved in G-protein coupled receptors?

Answer 21

7-tm

Question 22

What are the examples of a Gs linked receptor?

Answer 22

B1- adrenergic receptor

Converts ATP to cAMP via adenyl cyclase activity, activates protein Kinase A

Question 23

What is the example of a Gi protein-linked receptor?

Answer 23

Inhibits adenyl cyclase, reduction in cAMP and PKA

M2 muscarinic receptor on heart

Question 24

What is the example of a Gq-protein linked receptor?

Answer 24

AT-1 antgiotensin receptor

Question 25

What is the function of phospholipase c?

Answer 25

Converts PIP2 to IP3 and DAG

Question 26

What is IP3 in regards to phospholipase C?

Answer 26

Secondary messenger

Question 27

What does IP3 stimulate?

Answer 27

Calcium release

Question 28

What are enzyme-linked receptors?

Answer 28

Ligand binding –> receptor clustering activates enzyme activity with the cytoplasmic domain
Enzyme phosphorylates receptor
Phosphorylation of receptor leads to binding of signalling proteins to cytoplasmic domain
Signalling proteins recruit other signalling proteins
Signal terminates when a phosphatase dephosphorylates the receptor

Question 29

How is the signal terminated in enzyme-linked receptor signaling?

Answer 29

Phosphatase enzyme dephosphorylates receptor

Question 30

What are type-1 intracellular receptors?

Answer 30

Cytoplasmic
Located within the cytosolic compartment associated with chaperone molecules
Chaperone molecules involved in conformational folding
Hormone complex bind to receptor (heat shock proteins dissociate)
Behave as transcriptional factor upon binding to promoter region

Question 31

What are chaperone molecules?

Answer 31

Heat shock proteins associated with steroid hormones

Chaperone molecules assist with conformational change of hormone

Question 32

Which type of hormone acts on intracellular receptors?

Answer 32

Steroid hormones are membrane-permeable

Question 33

What are the examples of steroid hormones?

Answer 33

Cortisol, and corticosteroids

Question 34

what are type-2 intracellular receptors?

Answer 34

Nuclear, hormone ligand forms complex within the nucleus, binding to the transcriptional region.