Transcript Unit 3
3.(a) Periodic Table, Isotope abundance chapter 3 (b) Origin of Food A group of elements consists of all the elements in any vertical column of periodic table. The elements in each horizontal row of the periodic table represent a period. The Periodic Table(see www.webelements.com) Isolation of Elements • He from natural gas-looming shortage (escapes from the atmosphere) • Ne, Ar, Kr, Xe come from fractional distillation of liquid air • Radon (Ra) comes from radioactive decay of radium • Halogens found as ions in sea salt, ie NaCl, KI etc. Evaporation of Sea water • New Zealand Salt beds, sources of Cl, Br , I in salts The atomic weight of an element is the average of the mass of all of its isotopes, weighted for the abundance of each. If the atomic weight of Cl = 35.5 and Cl has two isotopes : 35 Cl 17 37 Cl 17 Approximately how much of each isotope occurs in natural abundance? Tough Question! • • • • Where to start? Any suggestions? If 50% of each isotope, atomic weight would be? Isotopes of Chlorine • Let fraction of 35Cl=x, thus fraction of 37Cl=1-x • So x(35) + (1-x)37= 35.5 • 35x +37 -37x = 35.5 • -2x= -1.5 • x=.75 Thus about 75 % 35Cl and 25 % 37Cl. Life’s Good things Come from Chemistry! C H O Co La Te Food: The Macronutrients • • • • • • Carbohydrates (4 calories/gram) Protein (4 calories /gram) Fats (9 calories/ gram) >99% of calories come from these ------------------------------------------------Micronutrients; Essential, but in much smaller amounts: Vitamins, Minerals Where does our food come from? .. . . .. - + . Origin of Carbohydrates: Photosynthesis • 6CO2 + 6H2O C6H12O6 +6 O2 • Glucose (a sugar) is formed • Reaction catalyzed by chlorophyll and requires sunlight • Balanced Equation: equal # of C, H, O on LHS and RHS Biosynthesis of Carbohydrates • Plants convert glucose to more complex sugars ie. cellulose, starch • Plants “fix” nitrogen from soil and air (78% N2, 20% O2, all others 2%) • Animals convert plants to protein and fats Biosynthesis of Fatty Acids • Complex: involve enzymes (catalysts) , ie Acetyl Coenzyme A. • Fats are biosynthesized by sequential addition of 2C units. • Palmitic acid –a C16 saturated fatty acid requires 8 Acetyl Co A units • Plants make these in their seed Biosynthesis of Fats in Plants Rapeseed (Canola) : source of a “healthy mixture of unsaturated fatty acids Biosynthesis of Protein • From amino acids • Human body can biosynthesize some proteins (for muscle, hair, hormones)