Chemical Principles

Atoms and Molecules: - A cell is more than a bag of chemicals - Important knowing how molecules interact Elements defined: Atoms defined: Molecule defined: Only ~16 of 92 naturally occurring elements are essential to most plants

Four major elements make up more than 95% of mass Hydrogen [H] Oxygen [O] Carbon [C] Nitrogen [N] Organic Compounds defined: Inorganic Compounds defined: Biochemicals defined: organic and inorganic molecules that occur in living things

Living things: 80% water, 20% organics Four Major Categories of Molecules: - Carbohydrates - Protein - Lipids - Nucleic Acids - Most of the mass is primarily these - Some other, lesser compounds: phenolics, alkaloids, terpenoids, and flavonoids Large Molecules: The Polymers Monomers: Polymers: (ex. Protein, DNA, lignin, tannin)

Carbohydrates: Sugars and starches: (ex. Glucose)(formula) Isomers: different compounds with the same formulas. Rarely found as monomers Sizes: monosaccharides disaccharides polysaccharides

Structural polysaccharides: hold cells and organisms together. (ex Structural polysaccharides: hold cells and organisms together. (ex. Cellulose fibers) Each cellulose fiber is composed of dozens of microfibrils Microfibril: 1000 or more cellulose polymers twisted together. Pectins: gluey polysaccharides that hold cellulose fibers together. Gums: complex, branched polysacs made of many kinds of monomers

2 important commercial polysacs agar and carrageenan Storage polysaccharides: store food Two most common in plants: Amylose and Amylopectin (starch) Ex. Monosaccharides: glucose and fructose Ex. Disaccharides: sucrose, lactose, maltose Ex. Polysaccharides: starch, glycogen

Proteins: 2nd in mass in plants after cellulose One or more polypeptides, sugars, or lipids Polypeptides – chain of amino acids (20 different ones to choose from) Used for: cell structure, storage, enzymes Protein Structure: Primary structure Secondary structure Tertiary structure Quaternary structure

Protein Denaturation Storage proteins: - nutrition source - seeds Ex. zein, gliadin Toxins: Ex. ricin D, abrin

Proteins in cell walls: - proteins are a major part of cell membranes and cell walls - 2-10% of cell wall protein Ex. Expansins and extensins (glycoproteins) Enzymes: catalysts - most of the proteins - proteases Ex. Alpha - amylase

Nucleic Acids: - most complex, polymer of nucleotides - two kinds: DNA and RNA - nucleotides: the monomers, 4 different kinds - DNA structure: the double helix - self-replicate - store information

Lipids: Are not polymers, water repellent 3 major plant lipids: Phospholipids Oils Waxes Very diverse Gives rise to more specialized cells Functions: storage, basic metabolism

Oils: Fats and Fatty Acids - liquid at room temperature (for plants) - triglycerides - structure: Saturated (bad fats) vs. Unsaturated (better) - most abundant in seeds

Phospholipids - hydrophilic and hydrophobic - major component of membranes - structure:

Waxes Mixtures of fatty acids and long chain alcohols. Epicuticular Layer: comprise the outermost layer (cuticle) of leaves, fruits, and stems Cuticular wax: embedded in the cuticle, primary layer of wax, 2 types Cutin: makes up most of cuticle Suberin: underground plant parts Waxes: more water repellent & harder than other lipids

Secondary Metabolites - Less made chemicals, scarce - Occur irregularly or rarely in plants - Byproducts of cell metabolism - No known role in cells for metabolism (?) Ex. Morphine, caffeine, nicotine, menthol - Most can be classified based on: 1. Kind of plant 2. Structure 3. Biosynthetic pathway

3 major groups of secondary metabolites 1. Alkaloids 2. Terpenoids 3. Phenolics Glycosides: secondary metabolites combined with one or more sugars for transport. Minor Secondary Metabolites - Nitrogen-sulfur compounds - Non-protein amino acids - Cyanogenics

Alkaloids - contain nitrogen in a ring structure - alkaline (basic) substances - bitter tasting - generally poisonous Ex. Coniine, strychnine, tomatine

Terpenoids Polymers, monomer called a isoprene Smallest called monoterpenes, 2 isoprene units (dimer), ex. Geraniol and Menthol Also diterpenes (pines) and triterpenes Sterols: kind of triterpene, similar to steroid hormones, ex. Digitalin Carotenoids: class of yellow to red pigments formed of 8 isoprene units Rubber: largest terpenoids there are (up to 6,000 or more monomers long)

Phenolics: - fully unsaturated carbon ring (phenol) linked to an oxygen Ex. Salicylic acid (aspirin) - subclass called phenylpropanoids involved in flavor Ex. Nutmeg flavor Others include: complex flavonoids, anthocyanins, tannin, lignin