Cellular Basics Recap

Vocabulary flashcards covering cellular mechanisms, programmed cell death, signaling pathways, lipid classes, and cell junction structures based on the lecture notes.

Apoptosis

Programmed cell suicide characterized by an intact cell membrane, the formation of apoptotic bodies, and non-toxic containment of internal components.

Necrosis

Uncontrolled cell death resulting from injury, characterized by the bursting of the cell membrane and the release of internal components into the surrounding environment.

Syndactyly

A condition resulting in fused digits caused by incomplete apoptosis during embryonic development.

Human Cell to Bacteria Count

The human body contains approximately $25 \times 10^{12}$ human cells and $38 \times 10^{12}$ bacterial cells.

Endocrine Signaling

Long-distance cellular communication where signal molecules travel through the bloodstream to reach target cells, producing a slower but longer-lasting response.

Paracrine Signaling

Short-range cellular communication where local signal molecules diffuse to nearby target cells, producing a rapid but short-lived response.

Autocrine Signaling

Cell signaling in which a cell secretes a chemical messenger that binds to receptors on its own cell surface to regulate its own functions.

Triglyceride

A major constituent of body fat consisting of one glycerol molecule attached to three hydrophobic fatty acid chains, serving as an energy reservoir.

Phospholipid

An amphiphilic membrane lipid composed of one glycerol molecule, two hydrophobic fatty acid tails, and one hydrophilic phosphate head group.

Amphiphilic

Describing a molecule that contains both a hydrophilic (water-loving) polar head group and a hydrophobic (water-repelling) non-polar tail.

Binding Specificity

The capability of a receptor protein to selectively bind a specific ligand among other molecules.

Binding Affinity

The measure of the binding strength between a ligand molecule and its specific receptor site.

Liposome

An artificial lipid vesicle consisting of a phospholipid bilayer enclosing an aqueous core, utilized for drug delivery to enhance stability and reduce non-specific toxicity.

Lipid Nanoparticles (LNPs)

Drug delivery vehicles composed of pegylated lipids, ionizable lipids, phospholipids, and cholesterol used to encapsulate fragile nucleic acids like siRNA or mRNA.

Gap Junction

An intercellular channel connection that allows small hydrophilic molecules, ions, and electrical signals to pass directly between adjacent cells.

Connexon

A hexameric protein channel subunit composed of 6 connexin proteins; two connexons in series span the membranes of two cells to construct a gap junction.

Tight Junction

An occluding cell junction that forms physical barriers to seal paracellular spaces between epithelial cells.

Desmosome

An anchoring cell-to-cell junction attached to intermediate filaments via dense plaques and cadherins, providing structural integrity in tissues under mechanical stress.

Membrane Potential

The electrical potential difference across a cell membrane, characterized by a negatively charged interior and a positively charged exterior environment.

Integral Protein

A membrane protein permanently embedded within or spanning across the phospholipid bilayer.

Transcellular Pathway

The pathway where substances pass directly through epithelial cells by crossing both apical and basolateral plasma membranes.