Lipids & proteins SBI 4U

Lipids – long term energy! Lipids are hydrophobic molecules Insoluble in water, but soluble in other non- polar substances Organisms need lipids for storing energy, building membranes and other cell parts, and as chemical signalling molecules Four families of lipids: fats, phospholipids, steroids and waxes

Fats! Most common energy-storing molecules in living organisms A very concentrated source of energy Excess carbohydrate is turned into fat – animals store fat molecules as droplets in the cells of adipose tissue

Fats, continued … Oil  plant equivalent to fat Triglycerides Both fats & oils composed of: glycerol and fatty acids Glycerol  3-carbon alcohol, each carbon attached to a hydroxyl group  with condensation reaction, 3 fatty acids attached to this core Fatty acid is a hydrocarbon chain, ending with a carboxyl group (-COOH)

Fats, continued

Saturated vs. unsaturated fats Saturated Fat: No double bonds between the individual carbon atoms. Ex: lard, butter, cream and fatty meats Unsaturated Fat: At least one double bond in the fatty acid chain. Ex: fish, canola oil and olive oil

Phospholipids A class of lipids that are a major component of all cell membranes Composed of: a glycerol molecule, two fatty acids and a highly polar phosphate group

phOSPHOLIPIDS CONTINUED… When added to water, phospholipids form spheres, called micelles – the hydrophilic heads stay in the water and their hydrophobic tails mix with one another in the center of the sphere

STEROIDS Compact hydrophobic molecules Cholesterol and sex hormones are examples of steroids Cholesterol is important for membrane permeability – too much can increase risk for heart disease and stroke Sex hormones (ex: testosterone & estrogen) control the development of sex traits and gametes

Waxes! Lipids containing long-chain fatty acids Firm and flexible consistency Produced by some animals (ex: bees) and plants Often used for commercial coating purposes Ex: cutin (produced by plants) helps protect surfaces of stems, leaves and fruits

What are proteins? Any of a large group of nitrogenous organic compounds that are essential constituents of living cells; consist of polymers of amino acids; essential in the diet of animals for growth and for repair of tissues; can be obtained from meat and eggs and milk and legumes; "a diet high in protein"

Proteins continued… They are amino acid polymers Structural characteristics determine function

Why are proteins important? Used as structural blocks Some are enzymes, that act as biological catalysts Help transport materials through cell membranes and through the bodies of plants and animals (ex: hemoglobin) Used in movement (major component of muscles) Antibody proteins for immune protection

Amino acids Building blocks of proteins

More about proteins! Amino acid polymers twist and coil into a particular shape that defines the protein An amino acid polymer is called polypeptide Peptide bonds are the bonds that hold amino acids together