Plasma Membrane Structure and Function Flashcards

This set covers the structural components, functions, and transport mechanisms of the plasma membrane as discussed in the lecture notes.

Colistin

A polypeptide antibiotic belonging to the polymyxin family that acts as a cationic surfactant by interacting with membrane phospholipids to alter permeability and cause bacterial death.

Compartmentalization

A function of the plasma membrane that allows for the creation of separate environments for different cellular processes in both prokaryotic and eukaryotic cells.

Biochemical Scaffolding

The role of the membrane in providing a framework for organized biochemical activities, such as the electron transport chain (Complex I, II, III, and IV) in the mitochondrial matrix.

Fluid Mosaic Model

The structural model of the plasma membrane proposed by Singer and Nicolson, characterized by a bilayer of phospholipids and a mosaic of various proteins.

Phospholipids

The core components of the lipid bilayer consisting of a phosphate polar head group, a glycerol backbone, and two fatty acid chains.

Sphingolipids

A class of lipids derived from sphingosine, including ceramide, sphingomyelin, cerebrosides, and gangliosides like $GM2$.

Integral Membrane Proteins

Proteins that penetrate the membrane's hydrophobic core, often containing one or more $\alpha$-helix segments.

Peripheral Membrane Proteins

Proteins located on the surface of the membrane that do not penetrate the lipid bilayer.

GPI-anchored Protein

A protein type linked to the membrane via a glycosylphosphatidylinositol anchor consisting of components like Man, GlcNAc, and Etn.

Unsaturated Fatty Acids

A component of membrane composition where higher amounts lead to increased membrane fluidity.

Cholesterol

A membrane lipid that affects fluidity; a higher quantity of this molecule results in lower membrane fluidity.

Active Transport

A transporter-mediated movement of substances across the membrane that require energy in the form of $ATP$, converting it to $ADP + P_i$.

Isotonic Medium

A solution (e.g., $0.15 \text{ M NaCl}$ for a cell with $0.15 \text{ M KCl}$) where there is no net loss or gain of water by the cell.

Hypotonic Medium

An environment with a lower solute concentration (e.g., $0.075 \text{ M NaCl}$) causing net water gain, cell swelling, and turgor (turgencia).

Hypertonic Medium

An environment with a higher solute concentration (e.g., $0.30 \text{ M NaCl}$) causing net water loss and cell shrinkage, known as crenation (crenación) in animal cells or plasmolysis (plasmólisis) in plant cells.

Liposomes

Synthetic vesicles used for drug delivery, which may contain a protective coating of polyethylene glycol, antibodies for targeting, and internal aqueous or lipid-soluble drugs.

Hypo-osmotic Swelling Test (HOS)

A test used to evaluate sperm membrane integrity by incubating samples in a $100 \text{ mOsm/L}$ solution of sucrose and sodium citrate for $30 \text{ min}$ at $37^\text{o}C$.