Overview
This lecture introduces biological molecules, focusing on monomers, polymers, and specifically monosaccharides, with detailed coverage of glucose and its isomers.
Monomers and Polymers
- A monomer is a small, single unit that can join with others to form larger molecules.
- A polymer is a large molecule made from many monomers bonded together.
- Common biological monomers include glucose (carbohydrates), amino acids (proteins), and nucleotides (DNA/RNA).
Carbohydrates Overview
- Carbohydrates contain carbon, hydrogen, and oxygen.
- Carbohydrates are classified by the number of units: monosaccharides (one), disaccharides (two), and polysaccharides (many).
- Monosaccharides are carbohydrate monomers; disaccharides and polysaccharides are formed from these monomers.
Monosaccharides
- The three AQA-required monosaccharides are glucose, fructose, and galactose.
- Glucose is the key monosaccharide found in all three major polysaccharides: starch, cellulose, and glycogen.
- The molecular formula for glucose is C₆H₁₂O₆.
Structure and Isomers of Glucose
- Glucose is a hexose (six-carbons) with five carbons in the ring and one outside.
- Carbon atoms in glucose are numbered starting from the right of the ring oxygen.
- Glucose has two isomers: alpha (α) and beta (β).
- Isomers have the same molecular formula but different structural arrangements.
- In alpha glucose, carbon 1 has hydrogen on top and hydroxyl (OH) below; in beta glucose, these are reversed.
Key Terms & Definitions
- Monomer — a small, single molecule that can join to form polymers.
- Polymer — a large molecule made from repeated monomer units.
- Carbohydrate — a molecule containing carbon, hydrogen, and oxygen.
- Monosaccharide — a single sugar unit, monomer of carbohydrates.
- Isomer — molecules with the same molecular formula but different structures.
- Alpha (α) Glucose — glucose isomer with hydrogen above and OH below on carbon 1.
- Beta (β) Glucose — glucose isomer with OH above and hydrogen below on carbon 1.
Action Items / Next Steps
- Memorize the three monosaccharides: glucose, fructose, galactose.
- Practice drawing the structure of glucose.
- Review the differences between alpha and beta glucose.
- Proceed to lessons on disaccharides and polysaccharides.
- Test your knowledge with practice questions.