Carbohydrates – Key Vocabulary

Vocabulary flashcards covering definitions and key characteristics of carbohydrate types, structures, reactions, and biochemical tests from the lecture notes.

Complex Carbohydrates

Long chains of sugar molecules that supply vitamins, minerals, and fiber; found in breads, legumes, rice, pasta, and starchy vegetables.

Simple Carbohydrates

Short-chain sugars that provide quick energy but few nutrients; present in fruits, milk, and refined sweets like cake and candy.

Monosaccharide

The smallest carbohydrate unit (single sugar) that is sweet, crystalline, water-soluble, and a building block for larger carbs.

Disaccharide

A carbohydrate composed of two monosaccharides linked by a glycosidic bond, e.g., maltose, sucrose, lactose.

Polysaccharide

Large carbohydrate made of hundreds of monosaccharides; often insoluble, not sweet, and used for energy storage or structure.

Triose Sugar

Monosaccharide with three carbon atoms, e.g., glyceraldehyde or dihydroxyacetone.

Pentose Sugar

Monosaccharide with five carbon atoms, such as ribose, deoxyribose, or ribulose.

Hexose Sugar

Monosaccharide containing six carbon atoms, notably glucose and fructose.

Aldose

A monosaccharide whose carbonyl group is an aldehyde at C1; examples include glucose and galactose.

Ketose

A monosaccharide with a ketone carbonyl at C2; example: fructose.

Reducing Sugar

Sugar with a free aldehyde or ketone group capable of reducing Cu²⁺ in Benedict’s test; all monosaccharides and some disaccharides.

Non-Reducing Sugar

Sugar lacking a free carbonyl group; sucrose is the main example and tests negative until hydrolyzed.

Glycosidic Bond

C–O–C linkage formed by condensation between two monosaccharides’ hydroxyl groups.

Condensation Reaction

Chemical process that joins molecules by removing water; forms glycosidic bonds in carbohydrates.

Hydrolysis

Reaction that splits molecules by adding water; breaks glycosidic bonds, reversing condensation.

α-Glucose

Isomer of glucose with the hydroxyl on C1 below the ring plane; forms starch and glycogen.

β-Glucose

Isomer of glucose with the C1 hydroxyl above the ring plane; monomer of cellulose.

Starch

Plant glucose storage polysaccharide composed of amylose and amylopectin.

Amylose

Unbranched, helical component of starch made of α-1,4-linked glucose units (~300 long).

Amylopectin

Branched component of starch; α-1,4-linked chains with α-1,6 branches every ≈30 glucose units.

Glycogen

Animal storage polysaccharide in liver and muscle; highly branched α-1,4 and α-1,6 glucose chains.

Cellulose

Structural polysaccharide of plant cell walls; straight β-1,4-linked glucose chains forming microfibrils.

Benedict’s Test

Chemical test for reducing sugars; blue Cu²⁺ solution turns green→brick-red precipitate when positive.

Iodine Test

Test for starch; iodine/potassium iodide forms a blue-black complex with starch.

Maltose

Reducing disaccharide of two glucose units joined by an α-1,4 bond; found in germinating barley.

Sucrose

Non-reducing disaccharide of glucose and fructose linked by an α-1,2 bond; main transport sugar in plants.

Lactose

Reducing disaccharide of glucose and galactose; primary sugar in mammalian milk.

Glycoprotein

Protein with oligosaccharide chains; important in cell membranes for recognition and signaling.

Glycolipid

Membrane lipid bearing carbohydrate chains that participate in cell recognition.

Carbonyl Group

Functional group (C=O) present as aldehyde or ketone in carbohydrates.

Hydroxyl Group

–OH functional group abundant in carbohydrate structures, conferring solubility.

Glycolysis Substrate

Role of glucose and other monosaccharides as starting fuel in cellular energy production.

Energy Storage

Function of starch in plants and glycogen in animals to reserve glucose for later use.

Structural Carbohydrate

Carbohydrates like cellulose that provide mechanical support in cell walls.

α-1,6 Branch Point

Glycosidic linkage that creates branches in amylopectin and glycogen chains.