d‑Glucose and its derivatives and analogues, N‑acetyl‐d‑glucosamine, N‑acetyl‐d‑muramic acid, d‑glucopyranosyl uronic acid, and d‑glucitol represent 99.9% of the carbohydrates on the earth. d‑Glucose is found in the free state in human blood and in the combined state in disaccharides, sucrose, lactose, and α,α‐trehalose, in cyclic dextrins, and in polysaccharides, starch, glycogen, cellulose, dextrans; N‑acetyl‐d‑glucosamine and an analogue N‑acetyl‐d‑muramic acid are found in bacterial cell wall polysaccharide, murein, along with teichoic acids made up of poly‐glycerol or ‐ribitol phosphodiesters. Other carbohydrates, d‑mannose, d‑mannuronic acid, d‑galactose, N‑acetyl‐d‑galactosamine, d‑galacturonic acid, l‑iduronic acid, l‑guluronic acid, l‑rhamnose, l‑fucose, d‑xylose, and N‑acetyl‐d‑neuraminic acid are found in glycoproteins, hemicelluloses, glycosaminoglycans, and polysaccharides of plant exudates, bacterial capsules, alginates, and heparin. d‑Ribofuranose‐5‐phosphate is found in many coenzymes and is the backbone of RNAs (ribonucleic acid), and 2‐deoxy‐d‑ribofuranose‐5‐phosphate is the backbone of DNA (deoxyribonucleic acid). d‑Fructofuranose is found in sucrose, inulin, and levan. The general properties and occurrence of these carbohydrates and general methods of isolation and preparation of carbohydrates are presented.