Lecture Notes: Protein Analysis and Plasma Membrane

Vocabulary flashcards covering key terms from notes on protein analysis methods, membrane structure, lipid types, membrane proteins, and related experiments.

SDS (sodium dodecyl sulfate)

An anionic detergent used to denature proteins and impart a uniform negative charge for separation by size in SDS-PAGE.

Disulfide bond

A covalent link between cysteine residues that can join protein subunits; reduced by beta-mercaptoethanol to separate subunits.

Beta-mercaptoethanol

A reducing agent that cleaves disulfide bonds in proteins, aiding denaturation for SDS-PAGE.

NCS

A chemical reagent used with beta-mercaptoethanol to help break disulfide bonds and separate protein subunits.

Polyacrylamide gel (PAGE)

Gel matrix used in electrophoresis to separate proteins by size; proteins migrate toward the anode when negatively charged by SDS.

Mass spectrometry

Analytical technique that yields a protein’s fingerprint by measuring mass-to-charge ratios, enabling identification via databases.

Mass spectrometry output

Pattern relating protein abundance to mass-to-charge ratio, used to identify the protein by database comparison.

X-ray crystallography

Technique to determine the 3D structure of proteins by diffracting X-rays through a protein crystal and computing the structure.

Single-domain protein family

Group of related proteins sharing one structural domain; knowing one domain’s function helps predict functions of others.

Differential centrifugation

Process to separate cellular components by sequentially increasing centrifugal force; larger components pellet first.

Nucleus

Large cellular organelle that pellets early in differential centrifugation; houses the genome.

Mitochondria

Energy-producing organelles that pellet at intermediate speeds during differential centrifugation.

Endoplasmic reticulum fragments

Pelleted material at higher speeds; small vesicles derived from the ER.

Ribosomes

Small particles of RNA and protein that synthesize proteins; pellet at very high speeds.

Plasma membrane

Phospholipid bilayer with embedded proteins; functions in import/export, signaling, and cell movement; described as fluid mosaic.

Phospholipid bilayer

Two-layer arrangement of phospholipids with hydrophilic heads facing water and hydrophobic tails inward; forms membranes.

Amphipathic

Molecule with both hydrophilic and hydrophobic regions; example: phospholipids.

Triglyceride

Lipid with glycerol backbone and three fatty acid chains; major storage fat.

Phospholipid

Lipid with two fatty acid tails, a glycerol backbone, and a phosphate-containing head; amphipathic and forms bilayers.

Choline-phosphate head

Polar head group of phospholipids consisting of choline linked to a phosphate; contributes hydrophilicity.

Hydrophobic tail

Nonpolar fatty acid chains that face inward in the bilayer, avoiding water.

Cholesterol

Amphipathic lipid interspersed in membranes; modulates fluidity by inserting between phospholipids.

Membrane fluidity

The ease with which lipids and proteins move within the bilayer; affected by lipid length, saturation, and cholesterol.

Lateral diffusion

Movement of lipids and proteins within the same leaflet of the membrane.

Flip-flop (transverse diffusion)

Movement of lipids from one leaflet to the opposite leaflet; rare because heads must cross the hydrophobic core.

Integral membrane protein

Protein permanently bound to the lipid bilayer, often spanning it; typically extractable only with detergents.

Peripheral membrane protein

Protein bound to membrane surfaces; easily released and not permanently embedded.

Transmembrane protein

Integral protein that spans the bilayer, with regions on both sides.

Alpha-helix transmembrane domain

Common structural motif in transmembrane proteins, where an alpha helix spans the bilayer.

Beta barrel

Beta-sheet–based transmembrane structure forming a pore for molecule passage through the membrane.

Receptor

Membrane protein that detects extracellular signals and relays messages inside the cell.

Membrane-associated enzyme

Enzyme located near or at the membrane surface, catalyzing reactions in its vicinity.

Anchor protein

Protein that connects membrane components to the cytoskeleton or extracellular matrix, stabilizing structure.

Actin and spectrin network

Cytoskeletal framework beneath the membrane; helps give cells like RBCs their shape.

Epithelial attachment to extracellular matrix

Membrane proteins that mediate adhesion of epithelial cells to the extracellular matrix.

Glycolipid

Carbohydrate-attached lipid on the cell surface; part of the glycocalyx.

Glycoprotein

Protein with attached carbohydrate; involved in cell recognition and signaling.

Glycocalyx

Carbohydrate-rich layer on the cell surface formed by glycolipids and glycoproteins.

Fluorescence recovery after photobleaching (FRAP)

Experiment where a membrane region is bleached with a laser and recovery shows lateral mobility of proteins.