Macromolecules 2: Lipids Grade 10 Biology

Your Assignment

Your Lipids Assignment 1. Define lipids— including information about solubility in water and their function. 2. Types of lipids—triglycerides, phospholipids, steroids 3. What are the main uses of lipids in cells (plants and animals)?

Additional Resources (1) The Tree of Life, lipids and Carbohydrates topic The Tree of Life

Additional Resources (2) Lipid informationavailable on the internet: Website links /3/ x.html /3/ x.html uRs&feature=related

Lipids: a diverse group of hydrophobic molecules Lipids are NOT polymers They are LARGE NONPOLAR ORGANIC molecules which are grouped due to their hydrophobic nature A diverse group of molecules: phospholipids, fats, oils, steroids, waxes, certain pigments Structurally, most lipids consist of 1 glycerol joined to 3 fatty acids Hydrophobic-- have little to no affinity to water Lipids consist mostly of hydrocarbons

Lipids Serve Many Functions Energy storage: store twice as many calories/gram as carbohydrates; one gram of any lipid will release 9 calories Protection of vital organs and insulation; in humans and mammals it is stored in adipose Lipids are used in biological membranes and as chemical messengers Structural: phospholipids are important part of cell membrane and the steroid cholesterol is a part of the plasma membrane of animal cells Endocrine system: some steroids are hormones that look like ‘chicken wire’ - 4 carbon rings

Energy storage in lipid Energy is stored in the C-H bonds  the fewer C-H bonds, the less energy stored in the molecule Lipid molecules use less OXYGEN than carbohydrates to store energy efficiently A gram of fat stores twice as much energy as a gram of polysaccharide

Hydrophilic vs Hydrophobic Hydrophilic = Water loving Hydrophobic = Water fearing

Fats (triacylglycerides) Not polymers: large molecules assembled from smaller molecules by dehydration synthesis Fats are made from a glycerol (a small 3C alcohol) and 3 fatty acids (a long carbon skeleton usually 16-18C long with a carboxyl end) joined by ester bonds. Fatty acids can be the same, or they can all be different

Fats (triacyglycerols or triglycerides) ENERGY STORAGE Large molecules created by dehydration reactions between smaller molecules, a glycerol and 3 fatty acids Fats differ in length of their hydrocarbon backbones and in presence and positions of double bonds – saturated fatty acids have no double bonds, unsaturated fatty acids have at least one.

Saturated and Unsaturated Fatty Acids Saturated fatty acids have no double bonds between carbons tend to be solid at room temperature linked to cardiovascular disease are commonly produced by animals Examples: butter and lard Unsaturated fatty acids have some carbon double bonds resulting in kinks tend to be liquids at room temperature are commonly produced by plants examples are olive and corn oils 15

What differentiates a saturated from an unsaturated fatty acid? Saturated/unsaturated

Saturated or Unsaturated Fatty Acids Stearic acid Solid at room temp SATURATED Oleic acid Liquid at room temp UNSATURATED

Lipids - Saturated and unsaturated

‘Hydrogenated’ oils Unsaturated fats have been synthetically converted to saturated fats by the addition of hydrogen. Peanut butter and margarine are hydrogenated to prevent lipids from separating out as oil. A diet rich in saturated fats may contribute to cardiovascular disease (atherosclerosis) through plaque deposits. The process of hydrogenating vegetable oils produces saturated fats and also unsaturated fats with trans double bonds. These trans fat molecules contribute more than saturated fats to atherosclerosis.

Phospholipid Phospholipid is glycerol, 2 fatty acids and a phosphate; bilayered with hydrophilic (phosphate) and hydrophobic portions (hydrocarbon); make up cell membranes

Phospholipids Similar to fats except they only have 2 fatty acids. The third space is filled with a phosphate group. Phospholipids are ampipathetic because they have a negative “head” portion which is hydrophilic and nonpolar “tail” portion which is hydrophobic

Phospholipids in Water When phospholipids are dropped into water, they form micelles or circles hiding their hydrophobic tails in the inside and their hydrophilic heads facing outward into the water. In cells, membranes of phospholipids form as a bilayer having the heads pointing out and into the cell (aqueous environments)

Phospholipids Molecular workbench P. 5, 6

Steroids Lipids characterized by a carbon skeleton made of 4 fused rings Steroids vary in the groups attached to these rings

Cholesterol Cholesterol is a steroid which is a common component of animal cell membranes keeping them fluid Many hormones including human sex hormones, are made of steroids: progesterone, testosterone, oestrogen etc