1.3 – Macromolecules

Macromolecules:
- large molecules composed of repeating sub-units
- Four major classes: - carbohydrates - proteins - lipids - nucleic acids

Reactions:
- Dehydration Synthesis (Condensation Reaction) - two subunits linked through the removal of a water molecule - absorbs energy
- Hydrolysis Reaction - two subunits break apart by addition of a water molecule - releases energy

Nutrients:
- Food  Energy
- healthy body requires about 50 nutrients
- grouped in 3 broad categories - vitamins/minerals - water - macromolecules

Carbohydrates:
- simple and complex sugar molecules
- most abundant macromolecule
- Polar molecules that are soluble in water (unless very large)
- used for energy, building materials, cell identification and communication
- contain carbon, hydrogen and oxygen (1:2:1 ratio)
- classified into 3 groups:
1. Monosaccharides
2. Oligosaccharides
3. Polysaccharides

Monosaccharides:
- When dissolved in water, sugars with 5 or more carbons form rings structures
- When dry, they form linear structures

- Aldose - All carbons have HYDROXYL groups attached, with the exception of CARBONYL group found on a terminal carbon

i. ii. - Ketose - All carbons have HYDROXYL groups attached, with the exception of CARBONYL group found on a central carbon

Oligosaccharides:
- 2 - 3 subunits
- A condensation reaction (dehydration synthesis) forms a glycosidic linkage between two monosaccharides to make an oligosaccharide

Polysaccharides:
- Many subunits (100’s to 1000’s)
- starch - Composed of amylose (α1-4 links) and amylopectin (α1-4 links but α1-6 links where it branches) - Energy storage for plants

- glycogen - Composed of α1-4 links but α1-6 links where it branches - More branched than starch - Animal energy storage

- cellulose - Composed of β1-4 links - Every other glucose subunit becomes inverted to accommodate this link - Not coiled or branched - Used in plant cell walls

- chitin - Cellulose-like polymer of Nacetylglucosamine - Monomer is a glucose molecule with a nitrogen containing group attached at second C position - Used to form hard insect exoskeletons - Used to make surgical thread

Lipids:
- Hydrophobic (water fearing)
- generally nonpolar & insoluble in water
- Includes fats, phospholipids, steroids and waxes
- 1g of fat stores 9 calories of energy (compared to 4 calories in carbohydrates and proteins)
- Used for energy storage, cushioning, and insulation
- Animals convert excess carbohydrates into fat (store the fat as droplets in the cells of adipose (fat) tissue)

Fats:
- backbone is GLYCEROL (has 3 hydroxyls)
- Each FATTY ACID has a terminal carboxylic acid, and between 16 and 18 carbons
- Condensation reaction attaches 3 fatty acids to glycerol making ester linkages (esterification)
- Saturated Fats
- come from animals
- Used for long-term energy storage, insulation, protection and helps dissolve fat soluble vitamins
- NO double bonds between carbon atoms in the fatty acids
- Solid at room temperature due to the straight chains à fatty acids are closer together à more intermolecular forces
- Unsaturated Fats
- comes from plant oils
- One or more double bonds between carbon atoms in fatty acids
- Double bonds form kinks - producing more space between fatty acids & reducing the number of intermolecular interactions
- Liquid at room temperature

Phospholipids:
- Composed of one glycerol, two fatty acids & a highly polar phosphate group
- Form cellular membranes (phospholipid bilayer)
- phospholipid bilayer - virtually impermeable to macromolecules - relatively impermeable to charged ions - quite permeable to small- lipid soluble molecules
- O2 and CO2 diffuse through with very little resistance
-