CHEM - LIPIDS

What is the Lipid?

a heterogeneous class of naturally occurring organic compounds classified together on the basis of common solubility properties:

• insoluble in water

• soluble in organic solvents (Et2O - diethyl ether, benzene and CHCl3, MeOH)

Common example of lipids

• fatty acids, triglycerides, sphingolipids, glycerophospholipids, glycolipids

• lipid soluble vitamins - A,D3, E, K

• Cholesterol

• steroid hormones

• prostaglandins (have 20 Carbons with a 5 carbon ring) - bone formation | leukotrienes & thromboxane

What is the dental related function of Prostaglandin E2 (PGE2)

bone formation

What is leukotriene?

a 20C fatty acid signalling molecule that plays a crucial role in inflammation and allergic reactions

What is Thromboxanes?

• group of lipid compounds containing 20C - ecosanoids (signalling molecules) from arachidonic acid

• plays a role in blood clotting and vasoconstriction

What lipids are present in saliva?

• fatty acids

• triglycerides

• glycerophospholipids

• sphingolipids and cholesterol

Note: ratios of these molecules changes during disease

What is Dental Calculus?

• formed by hardening of dental plaque

• contains 54.9% protein and 10.2% lipid

How do lipids correlate to carries in children?

• there is often a greater percentage of triglyceride in saliva of children who develop early childhood carries

What are the 5 functions of lipids?

1. Structure of membranes - separate cytoplasm from extracellular matrix

ex. phosphoglycerides, cholesterol

2. Intracellular storage of metabolic fuel (E) - in specialized fat cells

3. Transport of metabolic fuel

4. Insulation - preventing heat loss, injury barrier protection from nerve impulses

5. Chemical Signalling - hormones, prostaglandins, second messengers

What is another name from Glycerol?

propan-1,2,3-triol

What ar the 4 types of lipids?

1. Fatty acids (free and esterfied)

2. Lipids containing glycerol

3. Lipids without glycerol

4. Lipids combined with other types of compounds

Examples of lipids containing glycerol

• neutral fats: mono/di/tri-acylglycerols

• glycerphospholipids (phosphoglycerides)

Examples of Lipids without Glycerol

• Spingolipids

• Steroids

• Vitamins

Examples of lipids combined with other types of compounds

• lipoproteins (HDL, LDL)

What are fatty acids?

• long chain (n>10) carboxylic acids (COO-/COOH)

• usually have an even number of carbons (C12-C20) in an unbranched chain

• three most common: palmitic acid (16:0), stearic acid (18:0), oleic acid (18:1)

• can be saturated or unsaturated

How many carbons are present in palmitic acid?

16:0

How many carbons are present in stearic acid?

18:0 (saturated)

How many carbons are present in oleic acid?

18:1

What is the difference between saturated and unsaturated fatty acids?

• unsaturated fatty acids have a lower melting and boiling points than their saturated fatty acids (cut they are easier to break apart)

• more double bonds = lower melting point

What is the function of double bonds?

restrict the rotation of a molecule making less effective and makes molecules easier to melt

→ highly present in oils and fluid fats

How does chain length affect the water solubility of a fatty acid?

• increased chain length = decreased water solubility

How do double bonds affect water solubility of fatty acids?

increased double bonds = increased water solubility (more fluid molecule)

How does chain length affect melting point of a fatty acid?

increased chain length = increased melting point

How do double bonds affect boiling point in a fatty acid?

increased double bonds = decreased melting point

What are the 2 main general classes of lipids

→ Simple

→ Complex

What are the three types of simple lipids?

1. Fatty Acids

2. Fatty Acid Esters

3. Triglycerides

What are the types of complex lipids?

→ Phospholipids: Glycerophospholipids (has alcohol), Sphingolipids (has choline)

→ Glycolipids (has glucose)

What is a fatty acid ester?

• the acid component if the carbon fragment containing the C=O bond

• the alcohol component contains a -O-C linkage

What is advantageous of storing energy as carbohydrates?

• they are water soluble, allowing for easier absorption

What is advantageous of storing energy as fat?

You can store more energy/g meaning you can carry less weight around with more energy

What is the significance of phosphodiester linkage?

• forms the backbone structure of DNA, RNA and nucleotides (ATP)

What are the P-O-P linkages in phosphoric esters (ie.ATP)

high energy anhydride bonds

Triglycerides

• animal fats and vegetable oils

• fatty acid tri-esters

• animal fats store twice as much energy per gram as carbohydrates (9kcal/g vs. 4kcal/g) - less weight to mole around per kcal of energy stored

Phosphoric acid (H3PO4)

• forms mono/di and triphposphoric esters

What is Phosphoester linkage?

• forms the backbone structure of DNA, RNA and nucleotides (ATP)

• the P-O-P linkages are high energy anhydride bonds -phosphoanhydrrides

What is a triglyceride?

• an ester of glycerol with three fatty acids

• aka triglycerols

• most abundant lipid in humans

• found in:

  • major deposition lipid - adipocytes

  • major dietary lipid (>90% if lipids)

  • major transport form - chylomicrons

• melting point increases as the number of carbons increases

• melting point increases as the number of double bonds decreases

ex. oils - rich in unsaturated fatty acids (generally liquid @ room temp.)

What is this molecule?

glycerol

What % of daily calories do dietary lipids take up

~ 35% of calorific intake

What are fats?

• triglycerides rich in saturated fatty acids

• generally semisolid or solid at room temp

What are lipases?

enzymes that hydrolyze lipids and release the fatty acid components (triglyceride hydro

What molecules inhibits prostaglandin response?

aspirin