Physiology I - Cell Structure, Transport, Signaling, and Membrane Potentials

A set of vocabulary flashcards covering cell organelles, plasma membrane components, cellular transport, receptor types, signaling pathways, and membrane potentials based on the lecture notes.

Nucleus

Organelle that stores DNA, controls gene expression, and coordinates cell division.

Mitochondria

Organelles responsible for cellular respiration and apoptosis.

Rough Endoplasmic Reticulum

Organelle involved in secretory protein synthesis and ribosome attachment.

Smooth Endoplasmic Reticulum

Organelle involved in lipid synthesis and calcium storage.

Golgi Apparatus

Organelle that serves as a pathway for proteins from ribosomes to be secreted or sent to the cell membrane, functioning to modify, sort, and package proteins.

Lysosomes

Organelles responsible for intracellular digestion.

Peroxisomes

Organelles responsible for breakdown of cellular components via oxidation.

Vacuoles

Organelles responsible for the storage of nutrients and waste products.

Chromatin

Form of genetic material in active use that is ready to be used by the cell.

Chromosomes

Structures that serve as reservoirs of genetic material.

Cytoskeleton

Cellular framework composed of Intermediate Filaments, Microfilaments, and Microtubules that functions in cellular transport, movement, identification, structure, and stability.

Cholesterol (Plasma Membrane)

Membrane lipid component that increases membrane fluidity in heat and decreases rigidity in cold.

Integral Proteins

Proteins permanently embedded within the lipid bilayer (transmembrane or partially embedded on one side) that are strongly associated with the cell membrane and cannot be removed.

Peripheral Proteins

Proteins that do not cross the phospholipid bilayer, are subject to detachment, and often detach and attach to integral proteins.

Tight Junctions

Intercellular junctions that allow VERY little to no passage between cells.

Adherens Junctions

Intercellular junctions that provide cell-to-cell stability via actin filaments.

Desmosomes

Intercellular junction structures responsible for cell-to-cell adhesions.

Gap Junctions

Intercellular junctions for cell-to-cell communication that allow the most passage of substances between cells.

Hydrophilic (Lipophobic)

Water-liking, lipid-repellent substances that need assistance to pass through the plasma membrane and are often stored in vesicles.

Hydrophobic (Lipophilic)

Water-repellent, lipid-liking substances that do NOT need assistance to pass through the plasma membrane.

Osmolarity

Concentration of all osmoles per liter of solution, which is volume and temperature dependent.

Osmolality

Concentration of all osmoles per kilogram of solvent, which is volume and temperature independent.

Tonicity

Osmotic pressure gradient across a membrane that determines cell volume change.

Osmosis

Passive net movement of water across a semipermeable membrane.

Simple Diffusion

Passive transport along a pressure gradient (High to Low) requiring no assistance.

Facilitated Diffusion

Passive transport along a pressure gradient requiring assistance via channels (conformational change in plasma membrane) or carriers (binding and transporting target molecules).

Primary Active Transport

Movement of substances against a pressure gradient (Low to High) utilizing available energy directly from ATP.

Secondary Active Transport

Movement of substances against a pressure gradient using energy derived indirectly from ion charges (one moving down its gradient, the other being moved against gradient).

Transcellular Transport

Movement of substances across a cell, entering on one side (apical), traversing the cytoplasm, and exiting on the opposite side (basolateral).

Pinocytosis

"Cell drinking" — non-selective uptake of extracellular fluid via endocytosis.

Exocytosis

Vesicle-mediated fusion of intracellular vesicles with the plasma membrane to secrete contents outside the cell.

Transcytosis

Sequential endocytosis on one membrane domain, vesicular trafficking across the cell, and exocytosis on the opposite membrane domain.

Paracrine Signaling

Hormonal signaling where target cells are adjacent to the producing cell.

Autocrine Signaling

Hormonal signaling where the target cell is the same cell that produced the hormone.

Endocrine Signaling

Hormonal signaling where the target cell/tissue is distant and hormones travel via the bloodstream.

Ionotropic Receptors

Protein channel receptors that respond to hydrophilic ligands by opening large pores to allow passage of ions, altering cell membrane permeability.

Muscarinic Receptors

G-Protein Coupled Receptors (GPCR) that respond to hydrophilic ligands and initiate a secondary pathway for intracellular cascades.

Second Messengers

Intracellular molecules (such as cAMP, IP3, DAG, and $\text{Ca}^{2+}$) triggered by cell surface receptor-ligand binding.

Gs Protein

Stimulatory G-protein subunit that activates the cAMP pathway.

Gq Protein

Excitatory G-protein subunit that leads to IP3, DAG, and Calcium activation.

Gi Protein

Inhibitory G-protein subunit that inhibits the cAMP pathway.

Receptors Tyrosine Kinase

Transmembrane integral protein receptors activated by hydrophilic ligands that undergo dimerization and phosphorylation of all tyrosines, creating docking sites for signal relay proteins.

Intracellular Receptors

Receptors located on the nucleus or in the cytoplasm that require hydrophobic (lipophilic) ligands to freely cross the plasma membrane and alter gene expression in the nucleus.

Diffusion Potential

Difference in charges at which movement of ions begins.

Equilibrium Potential

Membrane potential where an ion has no net tendency to move because its chemical gradient and electrical gradient balance each other.

Membrane Potential

Charge at which a distinct polar zone is formed with different charges on either side of the cell membrane.

Resting Potential

Membrane charge at $-70\,mV$ when the cell is not excited or stimulated, maintained by Na/K ATPase pumps ($3\text{ Na}^+$ moved out, $2\text{ K}^+$ moved in) and K leak channels (highest contributor).

Absolute Refractory Period

Period during an action potential when voltage-gated $\text{Na}^+$ channels are inactivated and CANNOT be reopened, causing a directional propagation path away from origin.

Relative Refractory Period

Period during an action potential when voltage-gated $\text{Na}^+$ channels MAY be opened if a stronger than normal stimulus is received.

Depolarization

Phase of an action potential triggered at threshold ($-55\,mV$) where influx of $\text{Na}^+$ through open voltage-gated channels brings cellular charge to $\sim +30\,mV$.

Repolarization

Phase of an action potential where closure of $\text{Na}^+$ channels and efflux of $\text{K}^+$ through open channels brings cellular charge back to resting potential ($-70\,mV$).

Hyperpolarization

Phase of an action potential where continued efflux of $\text{K}^+$ just after resting membrane voltage was reached causes membrane potential to become more negative than normal resting potential (reaching $-90\,mV$).