Receptor Signalling

Question 1

What is cell signalling?

Answer 1

Release by one cell of substances that transmit information to other cells

Question 2

Define a ligand

Answer 2

Molecule that binds specifically/reversibly to another molecule to form a complex

Question 3

Define a receptor

Answer 3

Molecular structure within a cell/on the surface characterised by selective binding of a specific molecule and a specific physiologic effect that accompanies the binding

Question 4

What do receptors respond to?

Answer 4

Specific ligands, different cells respond differently to same ligand

Question 5

What is extracellular signalling?

Answer 5

These molecules are cues eg growth factors, hormones, cytokines, NT > Transmit specific info to target cells

Question 6

How are extracellular signalling molecules recognised?

Answer 6

By cognate receptors on surface of target cells to initiate intracellular signalling cascades elicit specific cellular responses

Question 7

Where are receptor found and their function?

Answer 7

Not all receptors exist on exterior of cell (some deep inside or in nucleus)
These receptors bind to molecules that pass through plasma membrane eg gases like nitrous oxide and steroid hormones eg oestrogen

Question 8

Describes ligand signalling

Answer 8

Binds specifically to receptor molecule
Changes properties of receptor
Ligand modified/degraded by cell to change/end response
Range of molecules act as ligands, various size, solubility, receptor location

Question 9

What are the different types of signalling?

Answer 9

Endocrine, autocrine, paracrine, signalling by plasma membrane-attached proteins

Question 10

What are the different types of cell-surface receptors?

Answer 10

G-protein coupled, tyrosine kinase, enzyme linked receptors, ion channels, toll-like receptors

Question 11

Describe adrenaline action

Answer 11

Fight/flight response
Orchestrated action eg - Inc heart rate, Inc glucose avaliability for muscle, Dec digestion
9 different receptors

Question 12

Describe the adrenergic receptor pathway

Answer 12

Adrenaline binds to adrenergic receptor activates G-protein complex
Alpha subunit dissociates with beta+gamma, associates with adenylyl cyclase activating it
Adenylyl cyclase converts ATP to cyclic AMP
cAMP stimulates further signalling cascade moves to nucleus with results in transcription of target gene
Endogenous GTPase hydrolyses GTP returning G-protein to pre-stimulated level of activity

Question 13

Describe enzyme linked receptors

Answer 13

Binding of ligand to external surface activates enzymatic activity inside cell
Only has one transmembrane domain

Question 14

What is the most comon enzyme linked receptor?

Answer 14

Tyrosine kinases

Question 15

Describe tyrosine kinases

Answer 15

Transfers phosphorus from ATP to protein molecules activating them
Occurs in pairs/dimerise on activation phosphorylating each other
Respond to growth factors, cytokines and hormones
Control many parts of cell/ organism growth, differentiation and function

Question 16

Describe epidermal growth factor receptors (EGFRs)

Answer 16

Regulates many transcription factors involved in cell proliferation
Hyper activation occurs if - Overexpression of receptor, Overproduction of ligand, Receptor mutation which causes signalling pathway to be continually active
Dysregulation lead to tumorigenesis
Overexpressed in cancers

Question 17

Describe Acetylcholine

Answer 17

Chemical released by nerve cells, send signals to other cells

Question 18

Describe Ach receptors

Answer 18

Membrane protein with aqueous pore running through it

Question 19

Describe ion channel activation

Answer 19

Soluble material eg ions can’t travel across membrane by passive diffusion
When Ach molecules bind to receptor, gated channel is open so ions flood into cell

Question 20

Where are toll-like receptors expressed?

Answer 20

On membrane of immune cells/non-immune cells eg epithelial, endothelial and fibroblasts
Receptor spans membrane with single pass

Question 21

Describe the activation of toll-like receptors

Answer 21

Activation leads to antigen induces signal pathway in cell dependant on type: Cytokine production, Proliferation, Extravasation pass through capillary via the vein eg exocytosis, Antigen presentation

Question 22

Describe the movement and activation of neutrophils through blood vessels

Answer 22

Rolling, Capture, Adhesion/Activation, Spreading, Extravasation (exo) > Phagocytosis

Question 23

How are signals initiated in cell signalling pathways?

Answer 23

By chemical interaction via many signalling molecules with a receptor on CS

Question 24

Describe the cell signalling pathways

Answer 24

Binding triggers chain of events that carries signal to cell interior/amplify it
Cells send signalling molecules to other cells - Chemical signals from NT travelling short distance, Hormones released from glands to blood for systematic response
Eg Receptor activated, Signal transduction, Regulates gene transcription, Commands cell activity

Question 25

What are the types of cell responses?

Answer 25

Synthesis and secretion of proteins
Growth/differentiation of tissues
Cell interaction with environment
Cell death/survival