Cell Physiology Part 4 Flashcards
What mediates intercellular communication in signal transduction?
Chemical messengers such as hormones, neurotransmitters, and cytokines.
What are the main pathways of cell membrane signal transduction?
- G-protein-linked receptor
- Ionotropic receptor
- Enzyme-linked receptor
What happens in G-protein-linked receptor signal transduction?
The receptor activates a G-protein, which in turn activates effector enzymes, leading to second messenger production and cellular response.
Name some G protein effector enzymes
Adenylyl cyclase (AC), Phospholipase C (PLC), Guanylyl cyclase (GC), Phosphodiesterase (PDE)
Name some common second messengers.
cAMP, IP3, DAG, cGMP, Ca²⁺
What are two key G-protein pathways?
• Receptor-G protein-AC
• Receptor-G protein-PLC
How do ionotropic receptors work?
They act as ion channels that open/close in response to specific signals (voltage, ligands, or intracellular messengers).
What are the types of ionotropic channels based on their activation?
• Voltage-gated
• Ligand-gated (extracellular signal)
• Signal-gated (intracellular
What is special about enzyme-linked receptors?
They have intrinsic enzyme activity and directly trigger enzyme signaling pathways.
Name types of enzyme-linked receptors.
• Tyrosine kinase receptor
• Guanylyl cyclase receptor
• Serine/threonine kinase receptor
• Non-receptor protein tyrosine kinase
Name five important ligands involved in cell signaling.
• Insulin
• Vascular Endothelial Growth Factor (VEGF)
• Platelet-Derived Growth Factor (PDGF)
• Epidermal Growth Factor (EGF)
• Macrophage Colony-Stimulating Factor (M-CSF)
What types of cells generate rapidly changing electrical impulses?
Nerve and muscle cells
What are local potential changes used for?
To transmit signals and control the function of cells
Do all cells have an electrical potential difference across their membrane?
Yes, all cells exhibit a membrane potential.
How is the membrane potential of a nerve fiber measured?
Using a microelectrode inserted into the nerve fiber
What causes the origin of the resting membrane potential?
•Unequal concentrations of Na⁺, K⁺, and Cl⁻ between extracellular and intracellular fluids
• different membrane permeabilities, with higher permeability to K⁺ than Na+at resting condition.
What are the two components of the electrochemical driving force?
Concentration difference and electrical potential difference
In electrochemical gradients, how do the concentration and electrical driving forces relate directionally?
They act in opposite directions
When is the electrochemical driving force equal to zero?
When the chemical and electrical driving forces are equal and opposite — this is the equilibrium potential (Eₖ)
What is the Nernst equation for calculating the equilibrium potential of potassium (K⁺)?
Eₖ = (RT / zF) × ln([K⁺]₀ / [K⁺]ᵢ)
What does a larger concentration gradient result in for an ion’s equilibrium potential?
A larger equilibrium potential
What determines how much an ion contributes to the resting membrane potential?
Its membrane permeability — the more permeable, the more influence
Which types of cells are considered excitable and can generate action potentials?
Nerve, muscle, endocrine, immune, and reproductive cells
What is polarization in terms of membrane potential?
The resting state of the membrane, typically around -70 mV
What is depolarization?
A decrease in membrane potential (inside becomes less negative, often due to Na⁺ influx)
What is repolarization?
Return of the membrane potential to resting state (mainly due to K⁺ efflux)
What is hyperpolarization?
Membrane potential becomes more negative than the resting potential
