The Chemistry of Life

ElementsC – carbonH – hydrogenO – oxygenN – nitrogenP – phosphorusS – sulfur

Major MacromoleculesMacromolecules are large organic (carbon-

containing) molecules. We will look at 4 kinds: 1. Carbohydrates2. Lipids3. Proteins4. Nucleic Acids

Many macro-molecules start as small monomers that grow into large polymers

monomers

monosaccharidesfatty acids and glycerol

amino acidsnucleotides

polymer

polysaccharidestriglycerides

polypeptides (proteins)nucleic acids (DNA, RNA)

H2OH2O

breakdown(hydrolysis)

formation (dehydration synthesis)

CarbohydratesElements• Carbon (C), hydrogen (H), oxygen (O)Types• Monosaccharides (e.g. glucose, fructose)• Disaccharides (e.g. sucrose)• Polysaccharides: starch, glycogen, cellulose,

chitinFunctions1. Energy supply (not cellulose or chitin) &

storage (glycogen in animals, starch in plants)2. Structural support in plant cell walls (cellulose)

and other organisms, such as lobsters (chitin)3. Provides dietary fibre for humans4. Deoxyribose and ribose in DNA and RNA

CarbohydratesMonomer

PolymerMonosaccharides are added together via dehydration synthesis (a condensation reaction).

glucose

Polysaccharides form when this process is repeated. For example, with glucose…

glucose fructose sucrose water+ +

monosaccharide disaccharide water+ + monosaccharide

dehydration synthesis

hydrolysis+ H2O

O O O O

+

OH

O

HO

bonds connect long

glucose chains

bonds link glucose

molecules

bonds in cellulose are hard to break

Cellulose

Glycogen

Starch

Elements• C and H, some O

(P, N in phospholipids)Types• Phospholipids

• Triglycerides• Waxes• SteroidsFunctions1. Long-term energy supply and storage2. Main structural component of cell membranes

(as phospholipids and cholesterol)3. Hormones such as testosterone and estradiol

Lipids

Hydrophobic tails (nonpolar)

Polar group

Phosphate

Glycerol

Fatty

acid

cha

in

Fatty

acid

cha

in

Hydrophilic head (polar)

LipidsMonomerThe closest thing to a monomer is a fatty acid:

PolymerLipids do not form polymers in the same way that carbohydrates, proteins, and nucleic acids do. The largest lipids are triglycerides:

Fatty acid

Glycerol

Fat molecule (triglyceride)

Lipids• Fatty acids can be saturated with H (all single

bonds) or unsaturated (some double bonds)• A double bond introduces an inflexible kink to

a molecule, preventing these molecules from getting close and making them more fluid

above: saturated fatty acids, as in butter (all C–C bonds)

right: unsaturated fatty acids, as in corn oil (some C=C bonds)

True or False Answers: 1 – 101. T – “organic” = “carbon-containing” (slide 2) 2. F – monomers join via dehydration synthesis

(2) 3. F – cellulose is indigestible by humans (3)4. T – indigestible cellulose provides fibre (3)5. F – two monosaccharides together is a

disaccharide; “poly” means three or more (4)6. T – types of macromolecules include proteins,

carbohydrates, lipids, nucleic acids (2)7. F – only C, H, and O are present (3)8. T – types of polysaccharides include starch,

glycogen, and cellulose (3)9. F – Cholesterol is a lipid (6)10. F – Fructose is a monosaccharide (4)

True or False Answers: 11 – 2011. F – Phospholipids have two fatty acids (6)12. T – Both provide energy (3,6)13. T – DNA has deoxyribose, RNA has ribose (3)14. F – Triglycerides have 3 fatty acids. Note:

“tri” = 3 and triglyceride = triacylglycerol (7)15. T – Listed as the second function of lipids (6)16. T – Look at the structure of glycerol; it has 3

carbons, 8 hydrogens, and 3 oxygens (7)17. F – Saturated fatty acids have all single bond (8)18. T – E.g., butter contains saturated fatty acids (8)19. F – Amino acids are monomers (2)20. T – Most bonds in unsaturated fatty acids are

single, but the double bonds cause bends (8)

Elements in the Human BodyOxygen (65%), Carbon (18%), Hydrogen (10%)

Nitrogen (3%)Calcium (1.5%)Phosphorus (1.0%)Potassium (0.35%)Sulfur (0.25%) Sodium (0.15%) Magnesium (0.05%)

Copper, Zinc, Selenium, Molybdenum, Fluorine, Chlorine, Iodine, Manganese, Cobalt, Iron (0.70%)

Lithium, Strontium, Aluminum, Silicon, Lead, Vanadium, Arsenic, Bromine (trace amounts)

Elements in the Body

Oxygen (65%) Carbon (18%) Hydrogen (10%) Nitrogen (3%) Calcium (1.5%) Phosphorus (1.0%) Potassium (0.35%) Sulfur (0.25%) Sodium (0.15%) Magnesium (0.05%) Copper, Zinc, Selenium, Molybdenum, Fluorine, Chlorine, Iodine, Manganese, Cobalt, Iron (0.7%)

Lithium, Strontium, Aluminum, Silicon, Lead, Vanadium, Arsenic, Bromine (trace amounts)