Cell Biology & Membrane Transport Flashcards

Vocabulary practice flashcards covering cell culture types, microscopy techniques, membrane lipid classes, lipid anchors, blood grouping, transport proteins, and ion pumps.

Primary Cells

Cells obtained directly from animal tissues that have a limited and finite lifespan in culture.

Transformed Cells

Cells derived from tumors or spontaneous oncogenic transformations that have an infinite lifespan, do not require a solid surface for growth, and can establish permanent cell lines like HeLa or HEK293.

Limit of Resolution ($D$)

The minimum distance between two objects at which they can still be distinguished as separate, calculated by $D = \frac{0.61\lambda}{N\sin(\alpha)}$; a smaller $D$ value indicates a higher resolution.

Wright-Giemsa Stain

A histologic stain used for blood and bone marrow cells that stains nuclei blue-violet and cytoplasm/erythrocytes pale pink, assisting in distinguishing red blood cells from white blood cells.

Benzidine Stain

A specialized staining technique that uses benzidine to identify cells in the erythrocytic series and detect hemoglobin deposits in histologic sections.

Confocal Laser Scanning Microscopy (CLSM)

A high-resolution optical imaging technique that uses pinholes to capture light from a specific focal plane while excluding out-of-focus light, generating 3D-like images with reduced photobleaching.

Fluorescence Resonance Energy Transfer (FRET)

A technique used to study protein-protein interactions by detecting energy transfer between two fluorescent molecules when they interact closely, causing a observable shift in emission wavelength.

Fluorescence Recovery After Photobleaching (FRAP)

A technique used to measure the lateral mobility and diffusion rate of proteins within cell membranes by monitoring the recovery of fluorescence in a laser-bleached region over time.

Total Internal Reflection Fluorescence (TIRF)

A specialized microscopy technique using an evanescent wave ($50\text{--}100\,\text{nm}$ penetration depth) to selectively excite fluorophores near the coverslip surface, ideal for studying cell surface movement.

Scanning Electron Microscopy (SEM)

An electron microscopy method that provides 3D surface images of specimens at a lower resolution compared to transmission electron microscopy.

Transmission Electron Microscopy (TEM)

An electron microscopy technique that generates 2D cross-sectional images of cell ultrastructure at very high resolution.

CRISPR vs RNA Interference (RNAi)

CRISPR targets and modifies genomic DNA directly, whereas RNAi (and shRNA) targets messenger RNA (mRNA) post-transcriptionally to regulate protein expression.

Phosphoglycerides

A class of amphipathic biomembrane lipids with a glycerol backbone, two hydrophobic fatty acyl tails, and a polar phosphate-containing head group; all phosphoglycerides are phospholipids.

Sterols

Amphipathic membrane lipids containing a rigid four-ring hydrocarbon structure and a polar head group that help protect membrane stability at low temperatures (e.g., Cholesterol in animals, Ergosterol in fungi, Stigmasterol in plants).

Acylation

A lipid modification mechanism where a protein is anchored to the cytosolic side of a membrane via a fatty acyl chain covalently bound to an N-terminal glycine (Gly) residue (e.g., v-Src).

Prenylation

A lipid modification mechanism where a protein is anchored to the cytosolic membrane face via an unsaturated hydrocarbon chain covalently linked to a C-terminal cysteine (Cys) residue (e.g., Ras GTPase family).

Glycosylphosphatidylinositol (GPI) Anchor

A glycolipid structure on the exoplasmic face of the membrane that anchors proteins covalently at their C-terminus using two fatty acyl chains inserted into the lipid bilayer.

ABO Blood Group System

A classification system based on erythrocyte surface antigens and plasma antibodies: Type A has A antigens and anti-B antibodies; Type B has B antigens and anti-A antibodies; Type AB has both antigens and no antibodies; Type O has no surface antigens and anti-A and anti-B antibodies.

Critical Micelle Concentration (CMC)

The concentration threshold of a detergent above which detergent molecules spontaneously self-assemble into micelles to dissolve membrane proteins, and below which they remain soluble as monomers.

Uniporter

A membrane transport protein that facilitates the movement of a single specific solute down its concentration gradient across a membrane.

Symporter

A cotransporter protein that moves two or more distinct species of solutes across a membrane in the same direction.

Antiporter

A cotransporter protein that moves two or more distinct species of solutes across a membrane in opposite directions.

Michaelis Constant ($K_m$)

The substrate concentration at which a transporter reaches half of its maximum transport velocity ($\frac{1}{2}V_{\max}$), representing the affinity of the transporter for its substrate.

P-class Pumps

ATP-driven ion pumps whose catalytic $\alpha$ subunit is transiently phosphorylated at an aspartate residue during the transport cycle (e.g., $\text{Na}^+/\text{K}^+$ ATPase and $\text{Ca}^{2+}$ ATPase).

V-class Pumps

ATP-powered proton pumps that transport $\text{H}^+$ ions into plant vacuoles, endosomes, and lysosomes to maintain low internal pH without forming a phosphorylated intermediate.

ABC Superfamily

A major class of ATP-dependent transport proteins containing ATP-binding cassette domains that transport small lipophilic molecules, amino acids, sugars, and peptides across cell membranes.

$E_1$ State

The conformation of a P-class pump in which high-affinity binding sites face the cytosol, allowing high-affinity uptake of specific ions (such as $\text{Ca}^{2+}$ or $\text{Na}^+$) prior to ATP-mediated phosphorylation.

$E_2$ State

The phosphorylated conformation of a P-class pump in which binding sites reorient toward the lumen or extracellular space with reduced affinity for cytosolic ions, causing ion release.

AE1 Protein

An anion exchange antiporter in red blood cell membranes that exchanges bicarbonate ($\text{HCO}_3^-$) for chloride ($\text{Cl}^-$) to support carbon dioxide transport in systemic and pulmonary circulation.

Transcellular Glucose Transport

The vector movement of glucose across epithelial cells from the intestinal lumen to blood via an apical $2\,\text{Na}^+/\text{glucose}$ symporter and a basolateral GLUT2 uniporter.