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

O

H2O

Glucose C6H12O6 Fructose C6H12O6

Sucrose C12H22O11 Water

• HYDROLYSIS: process that breaks the covalent bonds between monomers by the addition of water molecules

*Example: DIGESTION

OH2O

Sucrose C12H22O11Water

OH HO

Glucose C6H12O6 Fructose C6H12O6

Monosaccharides = single sugars

• are major nutrients for cells

• glucose is most common

*examples: glucose, ribose, galactose, fructose

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

http://www.sfu.ca/~fankbone/mollusca/chitin3rib.jpg

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

insoluble in water (because they are NONPOLAR, or HYDROPHOBIC)

include: 1. Fats

2. Phospholipids

3. 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

SATURATED FAT UNSATURATED FAT

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 FatsFunctions 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 …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)