NOTES: 2.3, part 1 - Macromolecules, Carbs & Lipids

The Chemistry of Carbon Why is CARBON so important to life? Living things are made up of molecules that contain CARBON and other elements (H, O, P, S, and N) Carbon atoms have 4 valence electrons, allowing them to form strong covalent bonds with many other elements Carbon has the ability to form millions of different large and complex structures!

Carbon’s 4 valence electrons:

Polymer Principles POLYMER: large molecule consisting of many identical or similar subunits connected together MONOMER: subunit or building block molecule of a polymer MACROMOLECULE: large organic polymer *Examples: carbohydrates, lipids, proteins, nucleic acids

POLYMERIZATION REACTIONS: chemical reactions that link 2 or more small molecules (monomers) to form larger molecules (polymers) DEHYDRATION SYNTHESIS REACTIONS (or CONDENSATION): reactions during which monomers are linked together; an –H and and –OH are removed, producing net removal of a water molecule for each covalent linkage

OH HO Glucose C6H12O6 Fructose C6H12O6 H2O O Sucrose C12H22O11 Water

HYDROLYSIS: process that breaks the covalent bonds between monomers by the addition of water molecules *Example: DIGESTION

H2O O Sucrose C12H22O11 Water OH HO Glucose C6H12O6 Fructose C6H12O6

Carbohydrates

Monosaccharides = single sugars are major nutrients for cells glucose is most common *examples: glucose, ribose, galactose, fructose ~OSE

Disaccharides = double sugars Also a source of energy Formed when 2 monosaccharides combine in a dehydration reaction; Examples:  lactose (milk sugar): glucose + galactose  sucrose (table sugar): glucose + fructose

Polysaccharides = hundreds or thousands of monosaccharides formed by linking monomers in DEHYDRATION SYNTHESIS REACTIONS.

Disaccharide

Examples of energy storage polysaccharides: starch = glucose polymer in plants used for energy storage (in roots, tubers, etc.) glycogen = glucose polymer in animals stored in skeletal muscles and liver of humans & other vertebrates

Examples of structural support polysaccharides: cellulose = structural component of plant cell walls that cannot be digested by most organisms chitin = forms exoskeletons of arthropods

Lipids!!

LIPIDS insoluble in water (because they are NONPOLAR, or HYDROPHOBIC)  include: Fats Phospholipids Steroids

1. FATS Composed of:  A large proportion of C-H bonds and less oxygen than carbohydrates (the nonpolar C-H bonds make the chain hydrophobic and insoluble in water)  Example: C57H110O6

during formation of a fat, dehydration synthesis reactions link fatty acids to glycerol

Fatty acids may vary in # of carbon atoms (usually even #)

Saturated vs. Unsaturated Fats  no C-C double bonds in fatty acid tail  usually solid at room temp.  most animal fats  e.g., bacon grease, lard, butter  one or more C-C double bonds in fatty acid tail  usually a liquid at room temp.  most plant fats  e.g., corn, peanut, olive oils

Functions of Fats energy storage (1 g of fat stores 2x as much energy as 1 g of carbohydrate) cushions vital organs in mammals (e.g. kidney) insulates against heat loss (e.g. whales, seals)

2. PHOSPHOLIPIDS Important component of cell membranes

3. STEROIDS Important component of some hormones

Cholesterol … is used to make many other steroids (including sex hormones in vertebrates) common component of cell membranes can cause atherosclerosis (if have too much)