UNIT%203%20%20CHEMISTRY%20OF%20LIPIDS

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UNIT 3 CHEMISTRY OF LIPIDS
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OBJECTIVES

• Define lipids and its occurrence
• State the biological significance of fats
• Define chemical composition of fats
• Define physical properties of fats
• Define chemical properties of fats
• Classify lipids into fatty acids, triglycerides,
  steroids
• Define phospholipids
• Describe the chemistry and functions of
  cholesterol
• Explain lipoproteins

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OBJECTIVES

• Define lipids and its occurrence
• State the biological significance of fats
• Define chemical composition of fats
• Define physical properties of fats
• Define chemical properties of fats
• Classify lipids into fatty acids, triglycerides,
  steroids
• Define phospholipids
• Describe the chemistry and functions of
  cholesterol
• Explain lipoproteins

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What are Lipids?

• Group of naturally occurring substances
• Consists of higher fatty acids
• Insoluble in water
• Soluble in Ether, chloroform, benzene and
  acetone (organic solvents)

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What are Lipids?

• LIPIDS Fatty acids, Triacylglycerols, Ketone
  bodies, Cholesterol, Phospholipids
  Sphingolipids
• Fats and Oils crude lipid mixtures from
  natural sources.
• Fats (solid) Oil (liquid) at room temperature

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Occurrence of Lipids?

• Widely distributed in plants and animals.
• Plants nuts, seeds and oils
• The Nervous system of Animals cholesterol,
  phospholipids and glycolipids
• Blood contains lipoproteins

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Occurrence of Lipids?

• Fat depots (large amount of fats)
• Subcutaneous tissues
• Mesenteric tissues
• Fatty tissues around the kidney
• Yellow bone marrow
• Food sources
• Milk, Egg, Meat, Liver
• Fish oils, nuts, seeds and oils

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OBJECTIVES

• Define lipids and its occurrence
• State the biological significance of fats
• Define chemical composition of fats
• Define physical properties of fats
• Define chemical properties of fats
• Classify lipids into fatty acids, triglycerides,
  steroids
• Define phospholipids
• Describe the chemistry and functions of
  cholesterol
• Explain lipoproteins

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Biological Significance of Fats

• Acts as fuel in the body. (caloric value 9
  Kcals/gm)
• Deposits of fats underneath the skin exert
  insulating effects.
• The mesenteric fat around organs (kidney)
  padding and protecting internal organs.
• Building materials. (cholesterol hormone
  synthesis)

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Biological Significance of Fats

• Lipids supply the essential fatty acids which
  cannot be synthesized in the body..
• The Nervous system is particularly rich in
  lipids.
• Vitamins A, D, E and K are fat soluble.
• ( lipid/fat is needed for absorbing these
  vitamins)
• Lipoproteins and phospholipids are important
  constituents of cell wall mitochondria.

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Biological Significance of Fats

• Adult ingests 60-150g of lipids per day of which
  90 is triacylglycerol (TAG).
• Balance cholesterol, cholestryl, esters,
  phospholipids and free fatty acids (FFA)

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Lipoprotein Phospholipids (cell wall
mitochondrion constituents)
Acts as fuel in the body
Insulating effect
Padding protection of internal organs
Vitamin A,D,E,K fat soluble vitamins
Building Materials (hormones)
Supply essential fatty acids
Nervous system Rich in lipids
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Classification of Lipids
LIPIDS
Simple Lipids
Compound Lipids
Derived Lipids
Substances Associated with Lipids
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Classification of Lipids
Classification Definition Examples
Simple Lipids Esters of fatty acids with various alcohols Neutral fats (F.A. alcohol) Glycerol (alcohol in fats) Anything other than glycerol (alcohol in waxes)
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Classification of Lipids
Classification Description 4 Sub-Divisions
Compound Lipids Contains other chemical groups in addition to alcohol and fatty acids Phospholipids Glycolipids Sulpholipids Lipoprotein
Phospholipids Glycolipids Sulpholipids Lipoprotein Contains fatty acids, glycerol, phosphoric acid nitrogenous compound (lecithin, cephalin) Lipids carbohydrate nitrogen but no phosphoric acid glycerol Lipids containing sulphate groups Attached to proteins (present in plasma tissues)
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Classification of Lipids
Classification Description
Derived Lipids Substances derived from simple compound by hydrolysis.
Examples
Derived Lipids Fatty acids Alcohols other than glycerol Glycerides Bases (choline, serine)
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Classification of Lipids
Classification Examples
Substances Associated with Lipids Carotenoids Tocopherols Vitamins A, D, E and K Steroids (Cholesterol)
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OBJECTIVES

• Define lipids and its occurrence
• State the biological significance of fats
• Define chemical composition of fats
• Define physical properties of fats
• Define chemical properties of fats
• Classify lipids into fatty acids, triglycerides,
  steroids
• Define phospholipids
• Describe the chemistry and functions of
  cholesterol
• Explain lipoproteins

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Chemical Composition of Fats
ANIMALS AND VEGETABLE FATS
Complex mixtures of glycerides
Triglycerides (TAG)- Neutral fats
Esters of glycerol fatty acids
3 molecules of fatty acids - glycerol
Triglycerides
One molecule of glycerol 3 molecules of fatty
acids (condensation)
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Chemical composition of lipids
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OBJECTIVES

• Define lipids and its occurrence
• State the biological significance of fats
• Define chemical composition of fats
• Define physical properties of fats
• Define chemical properties of fats
• Classify lipids into fatty acids, triglycerides,
  steroids
• Define phospholipids
• Describe the chemistry and functions of
  cholesterol
• Explain lipoproteins

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Physical Properties of Fats

• Greasy to touch and leaves an oily impression on
  paper.
• Are insoluble in water but soluble in organic
  solvents.
• Have less specific gravity than water (solid fat
  0.86), (liquid fat 0.95)
• Pure glycerides are tasteless, odorless,
  colorless and neutral in reaction (acidic-yellow
  color (hydrolysis oxidation)

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Physical Properties of Fats

• Flavor of butter is due to the presence of
  bacterial flora color of butter, human fat and
  egg yolk (due to presence of carotene
  xanthophil).
• Hardness and consistency depends on the amount of
  saturated and unsaturated fatty acids present.
  Saturated fatty acids are solid (room
  temperature) while Unsaturated fatty acids are
  liquid (room temperature) (e.g. oils)

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Physical Properties of Fats

• Fats have definite melting points.
• When liquid fat is placed on water- it spreads
  uniformly over the surface of water. If the
  quantity is small it forms a layer of 1
  molecule thickness (effect to lower surface
  tension- help transport fat)
• Though fat is insoluble in water- can be broken
  down into minute droplets and dispersed in water
  (emulsification)

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OBJECTIVES

• Define lipids and its occurrence
• State the biological significance of fats
• Define chemical composition of fats
• Define physical properties of fats
• Define chemical properties of fats
• Classify lipids into fatty acids, triglycerides,
  steroids
• Define phospholipids
• Describe the chemistry and functions of
  cholesterol
• Explain lipoproteins

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Chemical Properties of Fats

• Acrolein Formation glycerol ? heat potassium
  bisulphate
• Hydrogenation unsaturated fats
  (nickel-catalyst) saturated fats (hardening)
  e.g vegetable oil commercial cooking oil
• Saponification hydrolysis of fat by alkali
  (glycerol alkali salts soap)
• Rancidity chemical change resulting in
  unpleasant odor and taste on storage when fats
  are exposed to light, heat, air and moisture.
• E.g. Ascorbic acid (Vitamin C) and Vitamin E are
  antioxidants (prevents rancidity)

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OBJECTIVES

• Define lipids and its occurrence
• State the biological significance of fats
• Define chemical composition of fats
• Define physical properties of fats
• Define chemical properties of fats
• Classify lipids into fatty acids, triglycerides,
  steroids
• Define phospholipids
• Describe the chemistry and functions of
  cholesterol
• Explain lipoproteins

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Essential Fatty Acids (Polyunsaturated Fatty
Acids)
Lipids Examples Sources
Polyunsaturated Fatty Acids Linoleic acid Linolenic acid Arachidonic acid (not synthesized by the body- must be taken in the diet) Linseed Cotton seeds Peanuts Corn oils
Polyunsaturated Fatty Acids Linoleic acid the only fatty acid which is absolutely indispensable. Linseed Cotton seeds Peanuts Corn oils
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Triglycerides

• Neutral fat
• Concentrated source of energy
• used primarily for energy most common lipid in
  the body
• contain C, H, and O but less O than
  carbohydrates (C57H110O6)
• building blocks are 1 glycerol and 3 fatty acids
  per molecule saturated and unsaturated

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What are Steroids?

• Are non-saponifiable lipids
• Are biological compounds with diverse
  physiological activities
• Are compounds having a cyclopentanoperhydrophenant
  hrene ring system
• Has only a hydroxyl group (-OH) as its functional
  group (sterol, e.g. cholesterol)

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OBJECTIVES

• Define lipids and its occurrence
• State the biological significance of fats
• Define chemical composition of fats
• Define physical properties of fats
• Define chemical properties of fats
• Classify lipids into fatty acids, triglycerides,
  steroids
• Define phospholipids
• Describe the chemistry and functions of
  cholesterol
• Explain lipoproteins

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What are Phospholipids?

• Lipids containing phosphorus
• Are good emulsifying agents
• Found in cell membranes and in subcellular
  structures (lipid water interaction)

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OBJECTIVES

• Define lipids and its occurrence
• State the biological significance of fats
• Define chemical composition of fats
• Define physical properties of fats
• Define chemical properties of fats
• Classify lipids into fatty acids, triglycerides,
  steroids
• Define phospholipids
• Describe the chemistry and functions of
  cholesterol
• Explain lipoproteins

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What is Cholesterol?

• Are light yellow crystalline solid
• Are soluble in chloroform and other fat solvents
• Polyunsaturated acids lower the plasma
  cholesterol level
• The most abundant lipid in the human body

• Are synthesized in the liver, adrenal cortex,
  intestines, testes and skin.
• Play an important role as a component of
  biomembranes and has a modulating effect on the
  fluid state of the membrane.
• Can be estimated by color reactions (e.g.
  Liebermann-Burchard reaction) blue or green
  color

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Functions of Cholesterol

• An important tissue component (modulating effect,
  integrity permeability)
• Play an important role in insulating nerves and
  brain structure
• For transport of fatty acids in the body
• It is a part of lipoproteins

• It neutralizes the hemolytic action of various
  agents such as venom, bacterial toxins
• It gives rise to provitamin D
• It is a precursor of cholic acid in the body as
  also bile salts.
• It gives rise to sex hormones

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Functions of Cholesterol
Diabetes Mellitus
Atherosclerosis Plaque around The artery?
Hardening Narrowing
Myxoedema (Hypothyroidism)
CHOLESTEROL
Hyperthyroidism
Xanthomatosis (fat storage disorder)
Obstructive jaundice
Nephrotic syndrome (kidney disorder)
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OBJECTIVES

• Define lipids and its occurrence
• State the biological significance of fats
• Define chemical composition of fats
• Define physical properties of fats
• Define chemical properties of fats
• Classify lipids into fatty acids, triglycerides,
  steroids
• Define phospholipids
• Describe the chemistry and functions of
  cholesterol
• Explain lipoproteins

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What are Lipoproteins?

• Are conjugated proteins involved in transport and
  delivery of lipids to tissues.
• E.g. Lipids (Cholesterol triglycerides)
  water soluble carrier proteins
• It transport neutral lipids in the blood.
• It has lower density than the ordinary protein
  molecule.

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Distribution of Lipoproteins Body tissues
Cell membranes
Plasma Cholesterol, Phospholipids, neutral fat,
traces of fat soluble vitamins Steroid hormone
Nucleus, Mitochondria Microsome
LIPOPROTEINS
Rhodopsin (combination of protein, opsin and
retinal aldehyde of Vit. A
Thromboplastin (prothrombin-thrombin)
Egg yolk (HDL LDL)
Fat droplets in milk
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Lipoproteins according to Density
Type Density g/ml Protein Triglycerides (TAG) Cholesterol Cholesterol Phospholipids
Free Ester
Chylomicrons lt 0.95 1 85-95 1-2 1-2 3-6
Very low density lipoprotein VLDL 0.95-1.006 10 50-60 4-8 10 15-20
Low density lipoproteins LDL 1.006-1.063 22 10 10 38 20
High density lipoproteins HDL 1.063-1.21 45-60 3 5 15-20 25-30
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EVALUATION

• Give at least 3 importance of lipids.
• What are the 4 major groups of lipids?
• Give 2 examples of lipids?
• What are the functions of cholesterol?
• Differentiate steroid from cholesterol?
• Name 3 physical properties of fats?

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SPECIAL THANKS TO Sir Norman, Sir Joven, Ms.
Grace