Overview
This lecture introduces biological molecules, focusing on monomers, polymers, and the classification of carbohydrates, especially monosaccharides like glucose.
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 of many monomers bonded together.
- In biology, common monomers include glucose (carbohydrates), amino acids (proteins), and nucleotides (DNA/RNA).
Classification of Carbohydrates
- All carbohydrates contain carbon, hydrogen, and oxygen.
- Carbohydrates are grouped by the number of units they contain: monosaccharides (one), disaccharides (two), polysaccharides (many).
- Monosaccharides serve as the monomers for carbohydrates.
Types of Saccharides
- Monosaccharides: glucose, fructose, and galactose (must know these three for exams).
- Disaccharides: sucrose, maltose, and lactose (covered in the next lesson).
- Polysaccharides: starch, cellulose, and glycogen.
Glucose: Key Monosaccharide
- Glucose is the main monosaccharide found in all three polysaccharides.
- Its molecular formula is C6H12O6.
- The glucose molecule is a six-carbon (hexose) sugar, with five carbons in the ring and the sixth branching off.
- Glucose carbons are numbered starting to the right of the ring’s oxygen atom.
Isomers of Glucose
- Isomers are molecules with the same molecular formula but different structures.
- Glucose has two isomers: alpha-glucose (hydrogen on top, hydroxy on bottom at carbon 1) and beta-glucose (hydroxy on top, hydrogen on bottom at carbon 1).
- This structural difference is key for the function of each isomer.
Key Terms & Definitions
- Monomer — A small molecule that can bind to other molecules to form a polymer.
- Polymer — A large molecule comprised of many monomers bonded together.
- Carbohydrate — Organic molecule containing carbon, hydrogen, and oxygen, often as sugars and starches.
- Monosaccharide — A single sugar unit; a carbohydrate monomer.
- Disaccharide — Two monosaccharides bonded together.
- Polysaccharide — Many monosaccharides bonded together.
- Isomer — Molecules with the same molecular formula but different structures.
Action Items / Next Steps
- Memorize the three monosaccharides: glucose, fructose, and galactose.
- Practice drawing and labeling the structure of alpha- and beta-glucose.
- Review or proceed to the next lesson on disaccharides or polysaccharides.
- Test your knowledge with practice questions.