Biological Molecules: Professional Study Notes
Monomers and Polymers
Monomer: A small molecular unit that can join with other monomers through
condensation reactions to form polymers.
Polymer: A large molecule composed of many repeating monomer units.
Examples of Monomers: Monosaccharides, amino acids, nucleotides, fatty acids, and
glycerol.
Carbohydrates
Examples of Monosaccharides: Glucose, fructose, and galactose.
Alpha vs Beta Glucose: The difference lies in the orientation of the H and OH groups on
carbon 1. Alpha glucose has the OH group below the carbon, while beta glucose has the
OH group above.
Disaccharides: Carbohydrates composed of two monosaccharides linked by glycosidic
bonds.
Examples of Disaccharides: Sucrose = glucose + fructose; Lactose = glucose +
galactose; Maltose = glucose + glucose.
Polysaccharides: Carbohydrates made from many monosaccharides. Examples include
starch, glycogen, and cellulose.
Starch, Glycogen, and Cellulose
Starch: The storage form of glucose in plants.
Amylose: Long, unbranched chains of alpha glucose joined by 1,4-glycosidic bonds.
Forms a compact coil structure suitable for storage.
Amylopectin: Long, branched chains of alpha glucose with 1,4- and 1,6-glycosidic
bonds. Branches allow rapid enzyme action and glucose release.
Glycogen: The storage form of glucose in animals. Similar to amylopectin but more
highly branched for faster glucose release.
Cellulose: Long, unbranched chains of beta glucose joined by hydrogen bonds to form
strong microfibrils for structural support.
Food Tests
Reducing Sugars Test: Add Benedict’s reagent and heat. A positive result changes from
blue to brick red.
Non-Reducing Sugars Test: Add dilute HCl, neutralise with sodium
hydrogencarbonate, then add Benedict’s reagent and heat.
Starch Test: Add iodine dissolved in potassium iodide solution. Positive result: blue-
black; negative result: orange-yellow.
Lipid Test: Emulsion test: shake with ethanol, then add water. A cloudy/milky emulsion
indicates lipids.
Monomers and Polymers
Monomer: A small molecular unit that can join with other monomers through
condensation reactions to form polymers.
Polymer: A large molecule composed of many repeating monomer units.
Examples of Monomers: Monosaccharides, amino acids, nucleotides, fatty acids, and
glycerol.
Carbohydrates
Examples of Monosaccharides: Glucose, fructose, and galactose.
Alpha vs Beta Glucose: The difference lies in the orientation of the H and OH groups on
carbon 1. Alpha glucose has the OH group below the carbon, while beta glucose has the
OH group above.
Disaccharides: Carbohydrates composed of two monosaccharides linked by glycosidic
bonds.
Examples of Disaccharides: Sucrose = glucose + fructose; Lactose = glucose +
galactose; Maltose = glucose + glucose.
Polysaccharides: Carbohydrates made from many monosaccharides. Examples include
starch, glycogen, and cellulose.
Starch, Glycogen, and Cellulose
Starch: The storage form of glucose in plants.
Amylose: Long, unbranched chains of alpha glucose joined by 1,4-glycosidic bonds.
Forms a compact coil structure suitable for storage.
Amylopectin: Long, branched chains of alpha glucose with 1,4- and 1,6-glycosidic
bonds. Branches allow rapid enzyme action and glucose release.
Glycogen: The storage form of glucose in animals. Similar to amylopectin but more
highly branched for faster glucose release.
Cellulose: Long, unbranched chains of beta glucose joined by hydrogen bonds to form
strong microfibrils for structural support.
Food Tests
Reducing Sugars Test: Add Benedict’s reagent and heat. A positive result changes from
blue to brick red.
Non-Reducing Sugars Test: Add dilute HCl, neutralise with sodium
hydrogencarbonate, then add Benedict’s reagent and heat.
Starch Test: Add iodine dissolved in potassium iodide solution. Positive result: blue-
black; negative result: orange-yellow.
Lipid Test: Emulsion test: shake with ethanol, then add water. A cloudy/milky emulsion
indicates lipids.
