Signalling Between Cells 2 Flashcards
What are ligands?
a molecule that binds to another (usually larger) molecule. Think of receptors
How do ionotropic receptors work?
Ligand binds to the receptor protein Change in conformation of channel protein opening of a pore Pore allows ions to move in or out of cell according to their respective concentration gradients
Name an example of ionotropic receptors ?
Nicotonic Acetylcholine
GABA reeptor A
Name the ligand, locatiob and physiological effect associated with Nicotinic Acetylcholine?
Ligand: Acetylcholine Location:Skeletal Muscle Physiological effect: Muscle contraction
Name the ligand, locatiob and physiological effect associated with GABA receptor A?
Ligand: (GABA) gamma amino butyric acid Location: Neuronal Physiological effect: neuronal excitability
How do G-proteins work?
7-TM receptor & heterotrimeric G-protein are inactive Ligand binding causes a change in conformation of receptor Unassociated G-Protein binds to the receptor causing GDP to be exchanged for GTP G-protein dissocaites into two active components -Alpha-subunit -Beta gamma subunit Causing the alpha subunit to bind to its target protein Internal GTPase activity on alpha-subunit dephosphorylates GTP to GDP Alpha subunit dissociates from target protein - inactive again because it binds to the Beta gamma subunit again Receptor remains active as long as ligand is bound and can activate further heterotrimeric G-proteins
Give examples of G protien linked receptors?
Examplesbeta1 receptor - Gs stimulate AC & increase cAMP & PKA M2 receptor - Gi inhibit AC & decrease cAMP & PKA AT-1 receptor - Gq activate PLC- hydrolyses PIP2 into IP3 & DAG.
What happens when an Gs protein linked receptor has binded with its ligand? Give an example of this type of receptor? State its effect ?
Stimulates adenylyl cyclase Converts adenosine triphosphate (ATP) to cyclic adenosine monophosphate (cAMP) cAMP activates protein kinase A (PKA) Example: Beta1-adrenergic receptor Effect: increase heart rate
What happens when an Gi protein linked receptor has binded with its ligand? Give an example of this type of receptor? State its effect ?
Inhibits adenylyl cyclase Reduces levels of PKA Example: M2-muscarinic receptor Effect: Decrease heart rate
What happens when an Gg protein linked receptor has binded with its ligand? Give an example of this type of receptor? State its effect ?
Stimulates phospholipase C (PLC) Converts PIP2 to IP3 and DAG IP3 stimulates Ca2+ release DAG activates PKC Example: AT-1 angiotensin receptor Effect: vasoconstriction
What are G-proteins receptors?
G protein–linked receptors (GPLR), constitute a large protein family of receptors that detect molecules outside the cell and activate internal signal transduction pathways and, ultimately, cellular responses.
Describe the process for enzyme-linked signal transduction?
Ligand binding receptors clustering Receptor clustering activates enzyme activity within cytoplasmic domain Enzymes phosphorylate receptor Phosphorylation binding of signalling proteins to cytoplasmic domain These signalling proteins recruit other signalling proteins signal is generated within cell equals an arrow
What is an enzyme linked receptor?
An enzyme-linked receptor, also known as a catalytic receptor, is a transmembrane receptor, where the binding of an extracellular ligand causes enzymatic activity on the intracellular side. Hence a catalytic receptor is an integral membrane protein possessing both enzymatic catalytic and receptor functions
Give an example of enzyme linked receptors and their physiological effects?
Insulin receptor (CD220 antigen) Ligand: Insulin Physiological effect: Glucose uptake ErbB receptors Ligand: Epidermal Growth Factor, Transforming Growth Factor Beta Physiological effect: Cell growth, proliferation
Name the two types of intracellular signal transduction?
Type1- Cytoplasmic Type 2-Nuclear
