Bio 93 Lecture 5: Single Cell Dynamics and Membrane Structure

Comprehensive vocabulary review flashcards for Lecture 5 covering single cell dynamics, fluid mosaic membrane architecture, membrane fluidity, experimental probes (FRAP, Frye-Edidin), protein classes, and biomedical applications.

Prokaryotic Cell

A type of cell lacking a membrane-enclosed nucleus ("before nucleus") and membrane-bound organelles, typically containing a nucleoid, ribosomes, plasma membrane, and cell wall.

Eukaryotic Cell

A cell that possesses a "true nucleus" bounded by a double membrane as well as specialized membrane-bound organelles.

Cytosol

The semifluid substance present in all cells in which subcellular components and organelles are suspended.

Carl Woese's Three Domains of Life

A biological classification system that organizes all cellular life into three distinct evolutionary domains: Bacteria, Archaea, and Eukarya.

Amphipathic

Having both a hydrophilic (polar, water-soluble) region and a hydrophobic (nonpolar, water-insoluble) region within the same molecule.

Fluid Mosaic Model

A membrane model describing the plasma membrane as a dynamic phospholipid bilayer containing a mosaic of proteins, glycolipids, and glycoproteins drifting laterally.

Plasma Membrane

A selective lipid barrier approximately $5\text{--}10\,\text{nm}$ thick that protects the cell, establishes an internal environment, and regulates substance transport.

Phospholipid

A lipid molecule consisting of a glycerol backbone linked to two fatty acid chains and a polar phosphate group attached to a variable chemical group.

Lateral Movement (Phospholipids)

The rapid sideways drifting of phospholipid molecules within their own leaflet of the bilayer, occurring at roughly $10^7$ times per second.

Flip-flop Movement (Phospholipids)

The transverse migration of a phospholipid molecule from one membrane leaflet across to the opposite leaflet, occurring rarely at about once per month.

Unsaturated Hydrocarbon Kinks

Structural bends caused by double bonds in fatty acid tails that disrupt tight lipid packing and maintain membrane fluidity at lower temperatures.

Cholesterol (Membrane Fluidity)

A steroid in animal cell membranes that reduces fluidity at moderate temperatures, but prevents tight packing and hinders solidification at lower temperatures.

Fluorescence Recovery After Photobleaching (FRAP)

An experimental technique that bleaches fluorescent molecules in a membrane area with a laser to measure diffusion rates by observing fluorescence recovery.

Frye and Edidin Experiment (1970)

An experiment fusing mouse and human cells into a hybrid heterokaryon, proving lateral membrane protein mobility as labeled proteins intermixed within $1\,\text{hour}$.

Integral Membrane Protein

A protein permanently inserted into the hydrophobic core of the lipid bilayer, frequently spanning both sides of the membrane.

Peripheral Membrane Protein

A protein that is not embedded in the lipid bilayer and instead associates loosely with the membrane surface through interactions with other proteins.

Glycoprotein

A membrane protein covalently bound to carbohydrate chains that project into the extracellular space.

Glycolipid

A membrane lipid covalently linked to carbohydrate moieties that faces the extracellular environment.

7-Transmembrane Domain Protein

A receptor protein containing amphipathic alpha helices spanning the membrane seven times, with hydrophobic residues contacting lipids and hydrophilic residues forming an interior core.

Membrane Sidedness Biosynthesis

The developmental principle in the endomembrane system where vesicle lumen-facing cargo and lipids become the extracellular-facing side of the plasma membrane after exocytosis.

Six Major Functions of Membrane Proteins

The six primary functional roles of membrane proteins: transport, enzymatic activity, signal transduction, cell-cell recognition, intercellular joining, and ECM attachment.

H Antigen

The basal carbohydrate structure present on red blood cells upon which ABO glycosyltransferases attach specific sugars to create blood group antigens.

ABO Glycosyltransferase

An enzyme coded by the ABO gene that attaches terminal carbohydrate units to the H antigen to determine human red blood cell types.

CCR5 Co-receptor

A host cell surface molecule that functions with CD4 to allow HIV entry; individuals lacking CCR5 are resistant to HIV infection.

Angiotensin-Converting Enzyme 2 (ACE-2)

A cell surface receptor distributed across various human tissues that the SARS-CoV-2 Spike protein binds to initiate host cell infection.

TMPRSS2

A host cell surface protease that cleaves and activates both the ACE-2 receptor and the SARS-CoV-2 Spike protein to facilitate viral entry into the host cell.

Chimeric Antigen Receptor (CAR) T-Cell Therapy

A therapeutic strategy where patient T cells are engineered with synthetic receptors targeting cancer antigens, triggering granzyme and perforin release to destroy tumor cells.

Saccharomyces cerevisiae

A single-celled eukaryotic fungus, commonly known as Baker's yeast, used widely as a biological model organism.

Nucleoid

The non-membrane-enclosed area within a prokaryotic cell where the bacterial chromosome is aggregated.

Phosphatidylserine

A primary membrane phospholipid that is asymmetrically concentrated in the inner (cytoplasmic) leaflet of animal plasma membranes.