cell signal and membrane Flashcards
(25 cards)
What does the K+/Na+ pump across the membrane?
K+ out of the cell (2K)
Na+ out of the cell (3Na)
What determines the intracellular and extracellular osmolarity?
IC= inorganic ions and impermeable ions EC= inorganic ions
Intracellular pH and why?
7.0-7.2 because cells produce acidic by-products resulting in a slightly more acidic ICF
What do the Na+/H+ and Cl-/HCO3- antiports transport?
Na+/H+= regulates ICF pH so pumps H+ out and Na+ in Cl-/HCO3-= regulates ICF pH so pumps HCO3- out and Cl- in
What dos the Na+/HCO3- symport transport?
They’re both transported into the cell
How is intracellular Ca2+ concentration regulated (2 pumps) ?
Na+/Ca2+ antiports transport Ca2+ out of the cell to maintain a low ICF concentration. This reduces background noise so a signal can be heard.
Ca2+ ATPase pumps also perform the same action but pump the calcium into ER/Mitochondria
Resting membrane potential equation
Nernst equation (look to lecture 2 for diagram)
Types of chemical cell signals
Paracrine: affects cells in the immediate vicinity of the cell that secreted it
Autocrine: the messenger also affects the cell that secreted it
Endocrine: Chemical messengers enter the blood and travel around the entire body
What are ligand agonists and antagonists?
Agonist are chemical that binds to the receptor, activating it naturally
Antagonists are chemicals that bind to the receptors, preventing the agonist from initiating a response.
What’s the difference between a ligand and agonist?
Ligand= occurs naturally Agonist= natural or unnatural
How are Receptor-Ion channels activated?
Agonist binds to receptor causing a conformational change, opening the channel
What happens when a receptor ion channel is activated?
Ions diffuse across the membrane initiating depolarisation, which in turn activates voltage-gated channels.
What do the majority of enzyme receptors initiate?
Protein Kinases to phosphorylate other proteins (autophosphorylation)
Exception: cyclase GMP has an intermediary
What is the largest class of cellular receptor?
G-protein linked receptors (a.k.a 7 transmembrane receptors)
Describe G-linked protein receptor structure.
3 subunits (alpha, beta and gamma) linked to a 7 alpha helix transmembrane receptor.
Describe the G-protein mechanism when activated by the receptor
1) Alpha subunit exchanges GDP for GTP.
2) The alpha subunit dissociates from beta and gamma; they both target other proteins.
3) GTP hydrolysed to GDP and the alpha subunit reforms with the beta and gamma subunits, ready to be activated again
How is adenyl cyclase activated (from cyclic AMP)?
G-protein alpha subunit activates it
What does adenyl cyclase convert and what does the product activate?
Converts ATP to cyclic AMP.
Cyclic AMP activates Protein Kinase A (PKA).
What breaks down cAMP and what is the product?
Phosphodiesterase and AMP
What process do G-protein linked receptors initiate?
Amplifying signalling cascade
Which type of G-protein is involved in the inositol triphosphate (IP3) signalling cascade?
Gq
What does Gq activate, and what action does this product perform?
Gq activates phospholipase C.
Phospholipase C converts PIP2 into inositol triphosphate and DAG.
What do IP3 and Diacylglycerol activate, respectively?
IP3: Endoplasmic reticulum calcium channels.
DAG: Protein kinase C (PKC).
What does PKC activate?
Protein Kinase C activates cellular Ca2+ receptors and channels, causing calcium ions to enter the cell
