CHEMISTRY OF CELLS CLASS 2A LEARNING OBJECTIVES To know the molecular structure and chemistry of water Polar molecule: H has slight positive charge, O has slight negative charge Most abundant molecule in cells (70 of cell weight) Molecules can either be hydrophilic (sugars, DNA, RNA, polar molecules, ionic substances, most proteins) or hydrophobic (hydrocarbons and lipids) Cohesiveness of H 2 results in surface tension, high specific heat and high heat of vaporization. Solution = mixture, solute = dissolved substance, solvent = liquid To understand the basic structure of carbon compounds Covalent bond: two atoms share outershell electrons. Carbon atoms can join to form skeletons such as chains, branched trees and rings. Hydrocarbons: carbon and hydrogen compounds which are nonpolar, dont form hydrogen bonds and generally insoluble. To be familiar with the concept of pH pH is the acidity of a solution and defined by the concentration of hydronium ions (H 3 ). For pure water [H+] = 10 molL therefore pH = 7. + pH = log[H3O ] Acid: release hydrogen ions. Base: reduce hydrogen ions. To know the structure of the building blocks of life including carbohydrates, lipids and proteins Sugars polysaccharides, glycogen and starch (in plants) Monosaccharides usually have the formula CH O. 2ither contain an aldehyde group (COH) or ketone group (CO) Disaccharides: carbon that carries an aldehydeketone reacts with hydroxyl on a second sugar. Maltose, lactose and sucrose. Oligosaccharides: short chain sugar molecules Polysaccharides: long chain sugar molecules. Fatty acids fats and membrane lipids Components of cell membranes Phospholipids: hydrophilic head, hydrophobic tail. 2 of the OH groups in glycerol are linked to fatty acids while the 3 is linked to phosphoric acid. Triacylglycerol: fatty acids are stored in cells (energy reserve) though an ester linkage to glycerol to form triacylglycerol. Amino acids proteins All amino acids have the general formula of H 2 C COOH. At pH 7 both amino and carboxyl groups are ionized. Grouped according to side chains: acidic, basic, uncharged polar and nonpolar. Amino acids are joined by an amide linkage called a peptide bond. N terminus (amino) on left, C terminus (carboxyl) on right. Nucleotides nucleic acids Nucleotide consists of nitrogencontaining base, 5 carbon sugar and one or more phosphate groups. Phosphates are joined to the C5 hydroxyl of the ribose or deoxyribose sugar. Nucleoside: no phosphate. Nucleotide: phosphate Functions: carry chemical energy in phosphoanhydride bonds, form coenzymes and used as small intracellular signalling molecules in the cell. To understand structure and function of ATP ATP molecules serves as an energy carrier in cells. Input of energy from sunlight or food creates ATP, ATP then releases energy available for intracellular work and for chemical synthesis turning back to ADP. To be familiar with the structure of DNA Pyrimidine: thymine, cytosine and uracil. Purine: adenine and guanine To appreciate the structure and role of macromolecules There are 3 families of macromolecules: polysaccharide, protein and nucleic acid. Macromolecules are polymers that are constructed from linking small organic molecules called monomers or subunits. Condensation reactions form polymers. Most proteins and many RNA molecules fold into only one stable conformation. Change in conformation can mean loss of function. Small subunits join together to form macromolecules (covalent bonds) which assemble into large macromolecular complexes (noncovalent bonds).