UNIT-IV-LIPIDS AND PORPHYRINS

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UNIT-IVLIPIDS AND PORPHYRINS



LIPIDS

� Lipids may be broadly defined as hydrophobic or amphiphilic

small molecules; the amphiphilic nature of some lipids allows

them to form structures such as vesicles, liposome's, or

membranes in an aqueous environment.

� Lipids are a chemically diverse group that share the samecharacteristic of being sparingly soluble in water and highly

soluble in non-polar organic solvents like acetone.

� The group has two major roles; in structure, particularly in the

membranous organelles and in energy storage as lipids

have a higher calorific value than carbohydrates.



Lipids:

1. Fatty acids 2. Neutral fats and oils

3. Waxes

4. Phospholipids 5. Sterols

6. Fat soluble vitamins



Saturated Fatty Acids

Octonoic Acid

CH3 CH2 CH2 CH2 CH2 CH2 CH2 C OH

O1245678 3



Unsaturated Fatty acid

Octenoic acid

O

O



Fatty Acids

R

N -p la E d - yd ph bic E d(Fat-s l bl tail)

P la E d -



Cis fatty acid-Oleic acid

O

CH3(CH2) C C (CH2) C O

HH

910



Trans fatty acid

OCH3(CH2)7 C C (CH2)7 C OH

H

H



Classification of lipids.

Simple lipids:

Fat & Waxes.

Derived lipids:

Steroids

Ketone bodies Fatty acids

Hormones

Lipids

Simple

lipids

Compound

lipids

Derived

lipids

Compound lipids

Phospholipids & Glycolipids

Sphingolipids & Sulpholipids

Lipoproteins & aminolipids



Simple lipids-Fats & Waxes

Triglycerides:

Major components of storage lipids in animals & plants.

98% dieatary lipids2%-Phospholipids-most abundant in lipids

Triglycerides are esters of glycerol with 3 fattyacid molecules.

Large quantities of triglycerides in the form of fat droplets.

Obese persons-supply the energy needs of the body for many months.

Whales,seals,penguins-padded with TG-to serve both (Energy storage & insulatingagainst low temperature)

Example for TG ± Oleodipalmitin,Oleopalmitostearin



Difference between Animal fat and plant fat

Animal f at

1. Rich in Saturated f atty acid

2. Ordinary room temp-solid

3. Low iodine number

4. Stored in liver & Bone marrow

5. Ex: Butter f at, beef f at

Plant f at (Oil)

1.Rich in unsaturated f atty acid

2.Ordinary room temp-liquid

3.High iodine number

4.Stored in seed & f ruits

5. Olive oil,soyabean oil. corn oil



Waxes(mixtures of ester)

Waxes are esters of fatty acids combined with long chain alcohols. Waxes are mainly

used as a waterproofing material by plants and animals, e.g. on leaves of plants and

on the feathers of animals.

Wax-means the material of the honeycomb. A number of waxes are produced commercially

in large amounts for use in cosmetics, lubricants, polishes, surface coatings, inks and many other

applications

These are esters of long chain saturated & unsturated fatty acid with long chainmonohydroxyalcohols.

Vertebrates waxes secreted by coetaneous glands (protective coating) to keep the

skin pliable, lubricated, waterproof.

Waterfowl birds-secrete waxes in their preen glands to make their feathers water ±

repellent.

Rhododendron-plant leaves are shiny because of the deposition of protective waxycoating.

Marine organisms (planktons) waxes act as a major food and storage lipids in them.



Compound Lipids(Membrane lipids)

Phospholipids, Glycolipids, Lipoproteins

Glycero

Phospholipids

Sphingo

phospholipids

Cerebrosides

Sulfatides

Gangliosides

Chylomicrons

LDL

HDL

VLDL



GlyceroPhospholipids

Phospholipids derived from glycerol.(e.g) choline,ethanolamine, or serine,

plasmolegens. Phosphoglycerides are derivatives of Phosphatidic acid.

Structure is similar to lecithin,cephalin but have one of the fattyacid is

replaced by an unsaturated ether.



Found in membrane contain 2-fattyacid molecules.

All phosphoglycerides have negative charge (PH-7)

Lecithin's: present in soybeans oil,nervous tissues and alsorequired for the normal transport and utilization of as other lipids.

Absence accumulation of lipids occurs in liver -giving rise to a

condition called ³fatty liver´.T

hey leads to fibrotic changes, cirrhosis.

II). Sphingo phospholipids: Sphingolipids are a class of lipids derived from the aliphatic amino

alcohol sphingosine.

These compounds play important roles in signal transmission andcell recognition



2.Glycolipids Lipids containing fattyacid, sphingosine alcohol,&CHO residue with nitrogenbase. sugar contain sphingolipids are called glyco sphingolipids-two main

groups:

neutral glycosphingolipids & acidic glycosphingolipids

They may contain one or more glycosyl moieties, hexose's but

eventually plus an additional hexosamine. According to the number of glycosyl units they are divided into:

- Monoglycosylceramides (one glycosyl unit)

- Oligoglycosylceramides (more than one glycosyl unit)

Deacylated glycosphingolipids (only one glycosylated sphingoid base)



Acidic glycosphingolipids sulf osphingolipides

phosphosphingolipids

phosphonoglycosphingolipids

gangliosides

Cerebrosides: Important components in animal muscle and nerve cell membranes

They consist of a ceramide with a single sugar residue at the 1-

hydroxyl moiety.

The sugar residue can be either glucose or galactose; the two

major types are therefore called glucocerebrosides andgalactocerebrosides.

Galactocerebrosides are typically found in neural tissue,

while glucocerebrosides are found in other tissues



Structure and Function of cerebrosides The fundamental structure of a cerebroside is ceramide

Sphingosine is the main long-chain base present in ceramide

Monoglycosyl and oligoglycosylceramides having a mono or

polysaccharide bonded glycosidically to the terminal OH group of ceramide is defined as a cerebroside.



Heam & cholorophyll

(photoreceptor )

Chlorophyll is the molecule that absorbs sunlight and uses its energy to synthesize

carbohydrates from CO2 and water.

This process is known as photosynthesis and is the basis for sustaining the life

processes of all plants.

Since animals and humans obtain their food supply by eating plants, photosynthesis

can be said to be the source of our life also.

Chlorophyll is the molecule that traps this 'most elusive of all powers' - and is called a

photoreceptor

The basic structure of a chlorophyll molecule is a porphyrin ring, co-ordinated to a

central atom. This is very similar in structure to the heme group found in hemoglobin, except that in

heme the central atom is iron, whereas in chlorophyll it is magnesium



Structure of chlorophyllTwo parts of chlorophyll

1.Porphyrin ring-(Mg) at its center

2. Hyrophobic phytol tail

Delocalized electron-

shared betweenseveral of C,H,N

Tail-20-Carbon-stabilizes the molecule in

the hydrophobic core of the thylakoid

membrane

CH3 group is present in chl ±a &

absorbs best at 450 and 680 nm

chl b absorbs best at 500 and 640

nm.



While chlorophyll a is directly involved in the redox reactions of the light reactions,

chl b functions as an accessory pigment,

Accessory pigments absorb light and pass the energy from the light to the chl a inthe reaction center.

Other accessory pigments can be present such as xanthophylls and the more well known carotenoids.

The most well known carotenoid is beta-carotene which absorbs diff erent wavelengths than the chlorophylls

Chlorophyll is one of the most important chelates in nature.

It is capable of channelling the energy of sunlight into chemical energy through theprocess of photosynthesis.

In photosynthesis, the energy absorbed by chlorophyll transforms carbon dioxide and

water into carbohydrates and oxygen. CO2 + H2O (CH2O) + O2

chlorophyll is at the center of the photosynthetic oxidation-reduction reaction

between carbon dioxide and water.



Haem prosthetic group that consists of an iron atom contained in the center of a large

heterocyclic organic ring called a porphyrin.



Structure of haem



Cholesterol

is a waxy steroid metabolite found in the cell

membranes and transported in the blood

plasma of all animals

cholesterol is an important component for

the manufacture of bile acids, steroid

hormones, and several fat-soluble vitamins

cholesterol is essential for all animal

life, it is primarily synthesized from

simpler substances within the body

For a person of about 68 kg typical

total body cholesterol synthesis isabout 1 g (1,000 mg) per day, and

total body content is about 35 g.

The plasma membrane of cells is

made of a combination of

glycosphingolipids and protein

receptors organized in glycolipoproteinmicrodomains termed lipid rafts

Within the cell membrane, cholesterol also

functions in intracellular transport, cell

signaling and nerve conduction



Cholesterol is a waxy, fat-like material that is found in all parts of the body. It comes

from two sources: 1.our liver produces it, 2.we consume it in meat and dairy products.

After a meal, dietary cholesterol is absorbed from the intestine and stored in the liver

.About 20±25% of total daily cholesterol production occurs in the liver ; other sites of high

synthesis rates include the intestines, adrenal glands, and reproductive organs

acetyl CoA +acetoacetyl-CoA, 3-hydroxy-3-methylglutaryl CoA (HMG-CoA

This molecule is then reduced to mevalonate by the enzyme HMG-CoA reductase.

3-isopentenyl pyrophosphate

farnesyl pyrophosphate Squalene

lanosterolcholesterol



Your heart is an amazing powerhouse that pumps and circulates 5 or 6

gallons of blood each minute through your entire body.



Heart disease begins when cholesterol, fatty material, and calcium build up in

the arteries, a process known as atherosclerosis.



Blockage of the coronary arteries by plaque may cause a heart attack

(myocardial infarction) or a fatal rhythm disturbance

(sudden cardiac arrest).



Doctors use a variety of tests to detect heart disease. One common test is the

electrocardiogram (ECG or EKG).

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UNIT-IV-LIPIDS AND PORPHYRINS