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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
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)
