B4: LIPIDSFATS!!

General Info. - Lipids

Organic molecules with long hydrocarbon chainsContains oxygen, carbon, and hydrogen

Soluble in non-polar solventsOrganic solvents

Insoluble in water Occur in only 3 forms

B.4.1: Compare the composition of the 3

types of lipids found in the human body.

3 types Triglycerides (aka fats and oils) Phospholipids (aka lecithin)

Steroids (aka cholesterol)

B.4.1. (Triglycerides)

Fat vs. Oil Fat saturated (Solid)

Oil unsaturated (Liquid)

Triglycerides are formed by CONDENSATION reaction between propane-1,2,3-triol (glycerol) and long chain

carboxylic acids (fatty acids)

B.4.1. (Triglycerides)

Can vary in length!

Always EVENLY numbered in length!

B.4.1. (Phospholipids) Integral part of all cell membranes Made of four components

GLYCEROL linked to TWO FATTY ACIDS and a PHOSPHATE

GROUP by esterification; phosphate is linked to a NITROGEN

CONTAINING ALCOHOL

B.4.2. (Phospholipids)

Choline GroupGlycerol

Fatty Acid Chain

B.4.1. (Steroids)

Also known as CHOLESTEROLHigh Density Lipid (HDL) Low Density Lipid (LDL)

Organic structure of 4 rings (always have 20

carbon atoms)

B.4.2: Outline the difference between HDL and LDL cholesterol and outline its

Both are LIPOPROTEINS Have SAME structure LDL transports CHOLESTEROL TO THE

ARTERIES where it lines the walls. Saturated fatsCardiovascular disease

HDL can REMOVE cholesterol from the

arteries and transport it back to the

B.4.3: Describe the difference in structure

between saturated and unsaturated fatty

Saturated Fatty Acid Every carbon has the maximum amount of hydrogens (SINGLE bonds only)

Unsaturated Fatty Acid DOUBLE bonds

LOWER MELTING POINT Creates a “kink” or a bend

STEARIC EFFECT (relevant to shape): the interjection of double bonded C atoms prevent the fatty acid molecules from approaching each other closely and hence interacting via Van der Waals’ forces.

B.4.3. (Saturated vs. SATURATED UNSATURATED

Type Molec.Structure Phys.Structure VanderWaals Mel7ngPoints

Saturated AllsinglebondsC‐C Straightchains Greater(moreatoms)strongerinterac9on

High(solidatroomtemp)

Unsaturated OneC=C(mono‐)orseveralC=C(poly‐)

Double‐bondsàkinkedchain

Lesser(feweratoms)weakerinterac9on

Low(liquidatroomtemp)

B.4.4: Compare the structures of the 2 essential fatty acids linoleic (omega-6) and linolenic

Linoleic (ω‐6faJyacid) POLY-UNSATURATED fatty acid Carboxylic acid with an 18 carbon chain and two cis- double bonds (C=C)

cis means on the same side The first double bond is located at the 6th carbon from the methyl end (aka- the omega end) and the second is located at the 9th.

Carboxylic Acidomega end

B.4.4. (Linolenic (ω‐3faJyacid) POLY-UNSATURATED fatty acid Carboxylic acid with an 18 carbon chain and THREE cis- double

bonds (C=C)

The first double bond is located at the 3rd carbon from the

methyl end (aka- the omega end), the second is located at the 6th, and the third is located at the 9th. (Multiples of 3!)

Carboxylic Acid

omega end

B.4.5: Define the term iodine number and calculate the number of C=C double bonds in

Unsaturated fats can undergo addition reactions

One mole of Iodine reacts with one mole of double bonds

Iodine is colored As reaction takes place, purple color disappears

Fats can be described by their iodine number

B.4.5. (Calculating Iodine

2 Titrations IBr and ICl mixed in glacial acetic acid Iodine is formed (YELLOW)

IBr and Icl mixed in glacial acetic acid + sample of FAT in solution Titrated w/ SODIUM THIOSULFATE Concentration of iodine is determined

Difference of concentration of AMOUNT OF IODINE (in 2 titrations)

Ratio of FAT: IODINE

B.4.6: Describe the condensation of glycerol and 3 fatty acid molecules to

Condensation WATER is formed ESTERIFICATION between the glycerol backbone and 3 fatty acid molecules

http://nutrition.jbpub.com/resources/animations.cfm?id=10&debug=0

Requires 3 FATTY ACIDS +

1 GLYCEROLGlycerol

(3 carbon

backbone

)

B.4.6. (Formation of

B.4.7: Describe the enzyme-catalyzed

hydrolysis of triglycerides during

Fats and oils are hydrolyzed by enzymes to GLYCEROL and FATTY ACIDS

Enzymes known as LIPASES This is the REVERSE of the formation of fats After hydrolysis, the products are broken down further by a series of REDOX REACTIONS

Produces CARBON DIOXIDE, WATER, and ENERGY

Fats are in a LESS OXIDIZED form than carbohydrates so the same weight of fat

B.4.7. (Triglycerides during

B.4.8: Explain the higher value of fats as compared to carbohydrates.

Fats Long hydrocarbon chains Mass mainly from CARBONS (oxygen: carbon ratio small)

CarbohydratesContain EQUAL proportions of carbon and oxygen and TWICE AS MUCH HYDROGEN atoms

Fats and Carbohydrates metabolize CO2 and H2O (products)

B.4.8. (Reasoning for Higher Amount of OXIDATION that takes place as the compounds are converted to CO2 and H2O (Fat needs more oxidation to occur) In fats most carbons are bonded to hydrogen atoms, so when fats are metabolized they form more new C-O bonds, releasing more energy than carbohydrates (where C-O bonds exist)

The bond enthalpy of the C-O bond is high, so when it forms a large amount of energy is released

Fat molecules require about half as much oxygen for the same number of carbon atoms OXIDATION OF FATS IS LONGER, but produces more energy

Cell Membranes (structurally) Phospholipids consist of a polar, hydrophilic phosphate ‘head’ and two hydrophobic fatty acid ‘tails’.

Phospholipid will always point toward water creates the structure of the PHOSPHOLIPID BILAYER

Energy Storage TRIGLYCERIDE LIPIDS

B.4.9: Describe the important roles of lipids in

the body and the negative effects they can

B.4.9. (“Good” Roles of Lipids)

Insulation and Protects Organs Adipose tissue (ADIPOCYTES)

Lipids are COVALENT COMPOUNDS that do

not conduct heat or electricity easily. Steroid Hormones

Cell-signalingHORMONE-PROTEIN COMPLEXES + frequency

Ω‐3faJyacidsreduce the risk of heart disease increasing circulation and breaking down the

B.4.9. (“Bad” Roles of Lipids)

Cholesterol + LDL A high-cholesterol diet can result in a high

concentration of LDLs in the bloodstream

(hardening and blocking)

Obesity Carbohydrates not metabolized as turned into

lipids via adipocytes (leading to increased body mass)

Increased body mass leads to strains on other body parts