Lipids

LIPIDS Elements: CHOP - mostly HYDROPHOBIC - MOSTLY hydrocarbons NET affect - NON-POLAR Types: fats and oils phospholipids steroids waxes

Function: 1. energy storage – fat and oil 2 Function: 1. energy storage – fat and oil 2. Protection and insulation - fat Ex: Blubber 3. structure – phospholipids and cholesterol 4. chemical communication - steroids 5. repel water- waxes

FATS AND OILS Structure - two parts 1. glycerol - three carbon chain with three hydroxyls 2. fatty acid - long chain of hydrocarbons with a carboxyl head carboxyl head combines with hydroxyl of glycerol by dehydration synthesis so 3 fatty acids combine with the glycerols = triglycerol or triglyceride The massive amounts of hydrocarbons in the tail make fats NONPOLAR

Fats and Oils Constructed from a glycerol and three fatty acids Result = TRIGLYCERIDE

FATS vs. OILS FATS - animal derived - solid at room temp OILS - mostly plant derived - liquid at room temp crucial difference? bonding in the fatty acids tails

- Fats are saturated - Oils are unsaturated both have the same basic structure of glycerol plus three fatty acids - fats: fatty acids are all single bonds making the chains essentially straight - pack together nicely - solid at room temperature - oils: fatty acids are unsaturated due to double bonds - causes the chains to bend in the cis conformation - don’t pack together very nicely – liquid at room temperature

(a) Saturated fat and fatty acid Saturated fatty acids Have the maximum number of hydrogen atoms possible Have no double bonds (a) Saturated fat and fatty acid Stearic acid Figure 5.12

(b) Unsaturated fat and fatty acid Unsaturated fatty acids Have one or more double bonds (b) Unsaturated fat and fatty acid cis double bond causes bending Oleic acid Figure 5.12

PARTIALLY HYDROGENATED OILS BAD BAD BAD BAD BAD

Hydrogenated Oils Unsaturated oils are heated and treated with hydrogen gas and a catalyst to break the double bond and add hydrogen - this makes them saturated Heating the oils can also cause isomerization and switch the cis double bond to a trans double bond making it a TRANS fat TRANS fats are not able to be processed by our cells and lead a higher interaction with “bad” cholesterol and can potentially lead to inflammation in the blood vessels exacerbating heart disease

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ENERGY Content of Foods - fats and oils: 9 Cal/g - carbs: 4 Cal/g - protein: 4 Cal/g - alcohol: 7 Cal/g

PHOSPHOLIPIDS Function: STRUCTURE - cell membranes Composition: Hydrophilic head: - phosphate joined to glycerol = POLAR - joins with other polar molecules Hydrophobic tail: two chains not three

(a) Structural formula (b) Space-filling model Phospholipid is amphipathic Both hydrophilic and hydrophobic CH2 O P CH C Phosphate Glycerol (a) Structural formula (b) Space-filling model Fatty acids (c) Phospholipid symbol Hydrophobic tails Hydrophilic head Hydrophobic tails – Hydrophilic head Choline + Figure 5.13 N(CH3)3

Reaction with water: heads out tails in 1. micelle 2 Reaction with water: heads out tails in 1. micelle 2. liposome - cell membrane – PHOSPHOLIPID BILAYER

Phospholipids in Water

The structure of phospholipids Results in a bilayer arrangement found in cell membranes Hydrophilic head WATER Hydrophobic tail Figure 5.14

Steroids four fused rings examples: testosterone estrogen cholesterol - stabilize cell membranes

Estradiol Testosterone CH3 OH HO O Estradiol Testosterone Female lion Male lion Figure 4.9

Cholesterol Is found in cell membranes Is a precursor for some hormones HO CH3 H3C

Understanding Blood Lipid Panel Total Cholesterol: Composite of triglyceride levels, LDL, and HDL Triglycerides: Normal Levels: 150 mg/dL Function: energy – body converts extra energy to triglycerides (fat) and stores it

LDL: Low Density Lipoproteins - “bad” cholesterol Function: transport cholesterol throughout the body for absorption by the cells Normal Levels: Between 100 – 129 mg/dL Issues: LDL bind more readily to the glycoproteins on the surface of the blood vessel endothelium (cell on the surface of the wall) and become oxidized  forms fatty plaques (atherosclerosis) that can harden (arteriosclerosis) to narrow the diameter of the blood vessels and make them less flexible (increases blood pressure)

HDL: High Density Lipoproteins “good” cholesterol Normal Levels: 40-50 mg/dL for men 50 – 60 mg/dL for women > 60 mg/dL = lower risk of heart disease Function: removal of lipids from the blood stream

Hypercholesterolemia Genetic condition that causes a lack of LDL receptors on the surface of cells Result in very high levels of cholesterol in blood

Animation of LDL receptors Receptor Mediated Endocytosis Part II

The deal with Fats Unconventional But Effective Therapy for Alzheimer's Treatment: Dr. Mary T. Newport at TEDxUSF