Introduction to Cell Regulation Flashcards
How do chemical synapses work?
- Action potential causes the release of the transmitter
- Binds to receptors usually with a gap between presynaptic and postsynaptic cells
How do electrical synapses work?
- Are physically connected and cause rapid responses.
- Transport across synapse occurs through gap junctions that act as connections between adjacent cells
What is autocrine signalling?
When a cell releases a chemical that affects own activity e.g interleukin-1
List four areas which chemicals can bind to to alter cellular activity
- Receptors
- Ion channels
- Transporters
- Enzymes
What factors are important for receptors?
- Type of response
- Specificity of binding site
What are the two major types of receptors?
- Intracellular e.g cause release of intracellular signaling proteins that alter cell behavior
- Cell surface e.g nuclear receptors - direct effect on gene expression to alter cell behavior
Describe ion channels
- Form an aqueous pathway through membrane
- Transition from open to closed
- Proteinaceous pores to regulate ion transport across plasma membrane
- Permeable to only one type of ion or permeable to a variety of ions
- Can be heteromeric - several different subunits come together in various combinations to form ion channel subtypes.
How can ion channels be distinguished?
- Gating mechanisms - can be voltage-gated (opened by membrane depolarisation) or ligand-gated (opened by binding of a ligand)
Give examples of voltage-gated ion channels
- Sodium ion channels - blocked by painkillers such as lignocaine to cause pain relief
- Calcium channels - targetted by antihypertensive and muscle pain relief drugs
- Potassium channels - targets of antiarrhythmic drugs
Give examples of ligand-gated ion channels.
- Nucleotide gated channels - activated by cAMP (Na+/K+ switching)
- Calcium activated channels - can bind to and activate K+ ion channels allowing movement of potassium ions
What are the 5 mechanisms of maintaining calcium levels in the cytoplasm?
- The Na+/Ca2+ exchanger on the cell membrane
- The Ca2+ pump on the cell membrane
- The Ca2+ pump on the ER
- The Ca2+ binding molecule
- The Ca2+ importer on mitochondria
Give an example of a molecule that has different effects across the body. Suggest a reason for this
In salivary glands, acetylcholine induces secretion. In heart muscle, it induces decreased rate and force of contraction. In skeletal muscle, it induces contraction.
This is due to the different receptors expressed within different tissues.
What are transporters with examples?
- Proteins that move ions in or out of the cell
- 3 TYPES - symporters, antiporters, exchangers
Suggest a possible mechanism of action for digoxin
- It works on the Na+/K+ ATPase to increase the levels of Na+ in the cell. This then increases the concentration of calcium ions within the cell. Increased binding of calcium ions to troponin C, causing increased contraction of cardiac muscle.
- Causes heartbeat to become more regular
Explain the significance of enzymes in both
- drug targeting
- physiological processes
- DRUG TARGETING - some drugs may inhibit enzymes or promote expression of the genes that code for the enzymes
- PHYSIOLOGICAL PROCESSES - enzymes can be involved in production of intracellular signalling proteins e.g the cleaving of PIP2 to form IP3 and DAG
