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

What is paracrine communication?

Answer 6

Denotes the secretion of hormones diffusion from the source to localized target cells

Question 7

Describe the paracrine communication involved in hyperglycemia:

Answer 7

Insulin secretion by B-cells in the islets of Langerhans

Inhibits glucagon secretion

Question 8

What is paracrine signalling?

Answer 8

Hormones act on adjacent cell

Question 9

What are the examples of paracrine communication?

Answer 9

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

Question 10

How do antigen presenting cells present antigens?

Answer 10

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

Question 11

What receptors bind to MHC Class 2 molecules?

Answer 11

TCRs

Question 12

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

Answer 12

Signalling between membrane attached proteins

Question 13

What is autocrine signaling?

Answer 13

Communication with self

Question 14

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

Answer 14

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 15

What are ionotropic receptors?

Answer 15

Ligand binding –> opens ion permeable pore traversing the membrane

Question 16

What is the structure of ionotropic receptors?

Answer 16

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

Question 17

Describe the sequence events upon ligand binding on ionotropic receptors?

Answer 17

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 18

What are the examples of ionotropic receptors?

Answer 18

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

Question 19

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

Answer 19

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 20

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

Answer 20

Alpha subunit

Beta & Gamma subunits

Question 21

What is associated with the alpha subunit?

Answer 21

GTP and GTPase

Question 22

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

Answer 22

7-tm

Question 23

What are the examples of a Gs linked receptor?

Answer 23

B1- adrenergic receptor

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

Question 24

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

Answer 24

Inhibits adenyl cyclase, reduction in cAMP and PKA

M2 muscarinic receptor on heart

Question 25

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

Answer 25

AT-1 antgiotensin receptor

Question 26

What is the function of phospholipase c?

Answer 26

Converts PIP2 to IP3 and DAG

Question 27

What is IP3 in regards to phospholipase C?

Answer 27

Secondary messenger

Question 28

What does IP3 stimulate?

Answer 28

Calcium release

Question 29

What are enzyme-linked receptors?

Answer 29

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 30

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

Answer 30

Phosphatase enzyme dephosphorylates receptor

Question 31

What are type-1 intracellular receptors?

Answer 31

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 32

What are chaperone molecules?

Answer 32

Heat shock proteins associated with steroid hormones

Chaperone molecules assist with conformational change of hormone

Question 33

Which type of hormone acts on intracellular receptors?

Answer 33

Steroid hormones are membrane-permeable

Question 34

What are the examples of steroid hormones?

Answer 34

Cortisol, and corticosteroids

Question 35

what are type-2 intracellular receptors?

Answer 35

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