Overview
This lecture covers the structure, classification, and functions of the four major groups of organic molecules essential for life: carbohydrates, lipids, proteins, and nucleic acids.
Organic Molecules: Definition and Types
- Organic molecules contain carbon and hydrogen, often with carbon-carbon bonds, and are associated with living cells.
- Molecules like COâ‚‚ and CO are not considered organic since they lack C-H or C-C bonds.
- The four macromolecule groups are carbohydrates, lipids, proteins, and nucleic acids.
Chemical Reactions: Dehydration and Hydrolysis
- Dehydration synthesis joins subunits (monomers) by removing water to form polymers.
- Hydrolysis breaks down polymers into monomers by adding water.
- Dehydration forms water as a byproduct; hydrolysis needs water to break bonds.
Carbohydrates
- Made of carbon, hydrogen, and oxygen with a 2:1 hydrogen to oxygen ratio.
- Monosaccharides are simple sugars (ex: glucose), usually with 3-7 carbons.
- Disaccharides consist of two monosaccharides joined by dehydration (ex: sucrose, lactose).
- Polysaccharides are long chains of glucose (ex: starch in plants, glycogen in animals, cellulose in plants).
- Glycogen in humans is always branched; cellulose cannot be digested by humans.
Lipids
- Lipids do not dissolve in water and include triglycerides, phospholipids, and steroids.
- Triglycerides have one glycerol and three fatty acids, joined by dehydration.
- Fats (solid at room temp, animal origin) and oils (liquid at room temp, plant origin) store energy.
- Saturated fatty acids have all single bonds; unsaturated have double bonds and are missing hydrogens.
- Trans fats are artificially produced and linked to heart disease.
- Phospholipids have a hydrophilic head and hydrophobic tail, forming cell membranes.
- Steroids are made of four fused carbon rings (ex: cholesterol, estrogen, testosterone).
Proteins
- Proteins support, catalyze reactions, transport, defend, and signal (hormones).
- Composed of amino acids linked by peptide bonds.
- Amino acids have a central carbon, amino group, acid group, R group (unique), and hydrogen.
- There are 20 amino acids in humans.
- Protein structure:
- Primary: linear amino acid sequence,
- Secondary: alpha helix or beta sheet,
- Tertiary: 3D folding,
- Quaternary: multiple subunits (ex: hemoglobin).
- Denaturation is the loss of a protein's shape and function due to heat, pH, or agitation.
Nucleic Acids
- Polymers of nucleotides (phosphate, five-carbon sugar, nitrogenous base).
- DNA stores genetic information; RNA has various roles including protein synthesis.
- DNA consists of deoxyribose sugar, bases (A, T, G, C), is double-stranded, and forms a double helix.
- RNA has ribose sugar, uses uracil instead of thymine, and is generally single-stranded.
- Complementary base pairing: A-T (DNA), G-C, and A-U (RNA).
- ATP (adenosine triphosphate) stores and transfers energy in cells; breaking a phosphate bond releases energy.
Key Terms & Definitions
- Organic Molecule — contains carbon and hydrogen; associated with life.
- Dehydration Reaction — joins monomers by removing water.
- Hydrolysis — breaks polymers by adding water.
- Monosaccharide — simple sugar molecule.
- Disaccharide — two monosaccharides joined together.
- Polysaccharide — long chain of sugar units.
- Saturated Fatty Acid — no double bonds between carbons.
- Unsaturated Fatty Acid — contains double bonds; fewer hydrogens.
- Peptide Bond — bond between two amino acids.
- Denaturation — loss of protein structure and function.
- Nucleotide — building block of nucleic acids (phosphate, sugar, base).
- ATP — molecule that stores and provides cellular energy.
Action Items / Next Steps
- Review definitions and structures of all macromolecule types.
- Ensure understanding of dehydration and hydrolysis reactions.
- Practice identifying the structures and functions of carbohydrates, lipids, proteins, and nucleic acids.
- Check food labels for nutritional content as suggested.