BI1.1 | Basic Biochemistry — Glossary

A carbon-containing molecule produced by living cells; the four classes are carbohydrates, lipids, proteins, and nucleic acids

The principle that a cell's physical structure directly determines its biological function — nothing inside a cell is randomly positioned

A membrane-bound compartment within the cell with a specific molecular composition and function, derived from Latin organella meaning 'little organ'

The double-membrane-bound organelle that stores DNA and serves as the site of transcription and mRNA processing

Double-membrane organelles that generate ATP through oxidative phosphorylation; contain their own circular DNA and are maternally inherited

A single-membrane organelle studded with ribosomes, responsible for synthesis and folding of secretory and membrane proteins

ER lacking ribosomes, responsible for lipid synthesis, steroid hormone production, drug detoxification (CYP450), and calcium storage

A stack of flattened membrane cisternae that modifies (glycosylation, phosphorylation), sorts, and packages proteins and lipids for their final destinations

Single-membrane organelles containing acid hydrolases at pH 4.5 that digest worn-out organelles, foreign material, and macromolecules

Single-membrane organelles containing catalase and oxidases for H2O2 metabolism and very-long-chain fatty acid beta-oxidation

Non-membrane-bound complexes of rRNA and protein that translate mRNA into protein; 80S in eukaryotes, 70S in prokaryotes

The Singer-Nicolson model (1972) describing the cell membrane as a fluid phospholipid bilayer with mosaic-like proteins embedded within it

A self-assembling double layer of amphipathic phospholipids forming the structural backbone of all biological membranes

A membrane protein that spans the entire lipid bilayer with hydrophobic transmembrane domains, including channels, carriers, and receptors

A membrane protein attached to the surface by electrostatic interactions, not embedded in the bilayer; examples include spectrin and ankyrin

The carbohydrate-rich layer on the extracellular surface of the cell membrane formed by glycoproteins and glycolipids, involved in cell recognition and protection

Energy-dependent movement of molecules against their concentration gradient using ATP; exemplified by Na+/K+ ATPase pumping 3 Na+ out and 2 K+ in

Passive transport of molecules across the membrane through protein carriers or channels along the concentration gradient without energy expenditure

Water channel proteins that allow rapid osmotic water movement across cell membranes

Cystic fibrosis transmembrane conductance regulator — a chloride channel protein whose dysfunction (ΔF508 mutation) causes cystic fibrosis

Metabolic reactions that break down complex molecules into simpler ones, releasing energy as ATP

Metabolic reactions that build complex molecules from simpler precursors, requiring energy input

A sugar tag added in the Golgi that directs newly synthesised acid hydrolases to lysosomes; defective tagging causes I-cell disease