Overview
This lecture covers the structure, types, and functions of carbohydrates, including their role in biological molecules, energy storage, structural support, and cell recognition.
Carbon and Biological Molecules
- Carbon forms four stable covalent bonds, allowing for complex and stable molecules.
- Biological molecules can have chain or ring structures based on carbon.
Macromolecules and Formation
- Macromolecules are large molecules made by linking smaller units called monomers.
- Polymers are chains of monomers formed via condensation reactions.
- Condensation reactions link molecules by removing a water molecule (H2O).
Types of Carbohydrates
- Monosaccharides are simple sugars (one unit), e.g., glucose.
- Disaccharides are two monosaccharides bonded together, e.g., maltose.
- Polysaccharides are many monosaccharides linked, e.g., amylopectin, glycogen, cellulose.
Bonds and Linkages
- Glycosidic bonds link monosaccharides via condensation reactions.
- 1,4 linkages create linear chains; 1,6 linkages create branches in molecules.
Glucose and Isomers
- Glucose is a six-carbon (hexose) sugar, chemical formula C6H12O6.
- Alpha and beta glucose differ in the orientation of the OH and H on the first carbon.
- Glucose is polar, water-soluble, and a major energy source when oxidized.
Hydrolysis and Digestion
- Hydrolysis adds water to break apart polymers into smaller units.
- Digestion involves hydrolysis reactions to break down large molecules.
Monosaccharide Types
- Trioses: three-carbon sugars.
- Pentoses: five-carbon sugars, e.g., ribose, deoxyribose.
- Hexoses: six-carbon sugars, e.g., glucose.
Polysaccharide Functions and Structures
- Cellulose: structural support in plant cell walls; made of beta-glucose, linear and forms hydrogen bonds.
- Starch: energy storage in plants, made of alpha-glucose; amylose (1,4 linkages, linear) and amylopectin (1,4 and 1,6 linkages, branched).
- Glycogen: energy storage in animals, similar to amylopectin but highly branched (more 1,6 linkages), made of alpha-glucose.
Glycoproteins and Cell Recognition
- Glycoproteins are proteins with attached carbohydrate chains, involved in cell recognition.
- Glycoproteins act as antigens for blood types (A, B, AB, O).
- Antigens on blood cells help the immune system identify self versus foreign cells.
Key Terms & Definitions
- Covalent Bond — a strong bond formed by sharing electrons between atoms.
- Monomer — a small, repeating molecular unit.
- Polymer — a large molecule composed of monomers.
- Condensation Reaction — process forming bonds with removal of water.
- Hydrolysis — reaction that adds water to break bonds in polymers.
- Glycosidic Bond — bond joining monosaccharides in carbohydrates.
- Isomer — molecules with the same formula but different structures.
- Antigen — recognition molecule on cell surfaces.
Action Items / Next Steps
- Review the structures and differences between alpha and beta glucose.
- Memorize functions and structures of cellulose, starch (amylose, amylopectin), and glycogen.
- Understand the role of glycoproteins in blood types and cell recognition.