Fats and Fatty Acids | Zoology Optional Notes for UPSC PDF Download

What are Fats?

• Fats are crucial for a healthy diet and serve as the most concentrated energy source, providing 8-9 calories per gram, compared to 4 calories per gram from carbohydrates and proteins.
• Composed of carbon, hydrogen, and oxygen, fats contain a higher ratio of carbon and hydrogen, leading to their high calorie content.
• Classified under lipids, fats combine both saturated and unsaturated types and are essential for energy in food.
• The body synthesizes two vital types of fats essential for inflammation control, blood coagulation, brain development, and more.
• Fats act as a storage system for excess calories, storing them in fat cells or adipose tissue, which also insulates the body.
• They play a key role in enabling the absorption and transportation of vitamins A, D, E, and K in the bloodstream.

Types of Fats

Saturated Fat:

• Linked to bad cholesterol and found in animal products like cheese, milk, and meat.
• Consumption should be limited due to the risk of heart disease from artery blockage by cholesterol.
• Unsaturated fats are recommended over saturated fats to lower cholesterol levels.
• Trans fatty acids from vegetable oils can also increase cholesterol.

Monounsaturated Fats:

• Healthy fats found in avocados, macadamia nuts, peanuts, olives, and olive oil.
• Beneficial for heart protection, insulin sensitivity, fat storage, weight loss, and energy levels.

Trans Fats:

• Also known as unsaturated fatty acids or trans fatty acids.
• Naturally occurring in beef, lamb, whole milk, cheese, cream, and butter.
• Conjugated linoleic acid, a type of natural trans fat, helps strengthen the immune system and prevent cancer.
• Most are artificially created through hydrogenation, turning liquid oils into solid fats (e.g., margarine, vegetable shortening).
• Found in processed foods, baked goods, and items fried in partially hydrogenated oils.

Polyunsaturated Fats:

• Healthy fats present in plant and animal foods, including vegetable oils, walnuts, flax seeds, and salmon.
• Include Omega 3 (reduces inflammation, supports healthy hormone levels and cell membranes) and Omega 6 fatty acids (important for brain and muscle function).
• Small amounts of Omega 6 are needed, found in corn, soybean, safflower, cottonseed, grapeseed, and sunflower oils.
• Omega 6 is also in baked goods and packaged foods like cookies, crackers, chips, and french fries, which are not stable.

Essential Fatty Acids

• The body can synthesize most fatty acids except for three essential ones: Linoleic acid, Linolenic acid, and Arachidonic Acid.
• These essential fatty acids need to be obtained through dietary intake.
• Deficiency symptoms include poor growth and skin irritation.
• Such deficiencies have been observed in infants consuming formula without these essential nutrients.

Fatty Acid – Meaning and Definition

• Fatty acids are carboxylic acids with long aliphatic chains, which may be branched or unbranched.
• Naturally occurring fatty acids typically have even numbers of carbon atoms and are usually unbranched.
• They are key components of lipids.
• Fatty acids are found in three main ester forms: phospholipids, triglycerides, and cholesteryl esters.

Types of Fatty Acids

Fatty acids are categorized according to:

• Their carbon chain length.
• The number of carbon atoms they contain.
• Their level of saturation (saturated or unsaturated).

Even and Odd Chain Fatty Acids

• Most natural fatty acids feature an even number of carbon atoms in their aliphatic chains, such as oleic acid and stearic acid, both with 18 carbons.
• Odd-chain fatty acids (OCFA), which have an odd number of carbon atoms, exist as well; examples include heptadecanoic and pentadecanoic acids, found in dairy products.
• The biosynthesis process of odd-chain fatty acids is more complex compared to that of even-chain fatty acids.

Saturated and Unsaturated Fatty Acids

• Saturated fatty acids lack double bonds (C=C) in their aliphatic chains, with the chemical formula represented as CH3(CH2)nCOOH.
• Unsaturated fatty acids have at least one double bond in their aliphatic chain, leading to the formation of cis and trans isomers.

Cis isomers:

• Hydrogen atoms adjacent to the double bond are on the same side.
• Double bonds restrict the fatty acid's conformational freedom, making the molecule more rigid.
• A higher number of cis bonds results in a less flexible and more curved conformation.
• Examples include oleic and linoleic acids.

Trans isomers:

• Hydrogen atoms are positioned on opposite sides of the aliphatic chain, making the molecule straight.
• The trans configuration allows the structure to remain straight, similar to saturated fatty acids.
• Most naturally occurring unsaturated fatty acids are in the cis configuration.

Trans fats mainly result from human processing and are not commonly found in nature.

Length of Fatty Acids

Short-Chain Fatty Acids (SCFA):

• Have aliphatic chains of five or fewer carbons.
• Example: butyric acid.

Medium-Chain Fatty Acids (MCFA):

• Aliphatic chains consist of 6 to 12 carbons.
• Example: capric acid.

Long-Chain Fatty Acids (LCFA):

• Possess aliphatic chains of 13 to 21 carbons.
• Example: oleic acid.

Very Long Chain Fatty Acids (VLCFA):

• Aliphatic chains have 22 or more carbons.
• Example: lignoceric acid.

Properties of Fatty Acids

• Fatty acids generally have similar acidities.
• Increase in chain length reduces solubility in water but doesn't significantly affect pH of an aqueous solution.
• Example: Nonanoic acid (C9) with a pKa of 4.96, compared to acetic acid (C2) with a pKa of 4.76.

Hydrogenation:

• Unsaturated fatty acids are susceptible to rancidity through autoxidation or hydrolysis when exposed to air.
• Hydrogenation is used to reduce rancidity in unsaturated fatty acids.

Autoxidation:

• Unsaturated fatty acids can chemically change via autoxidation in the presence of air and trace metals.
• Treatment with chelating agents can prevent autoxidation by removing metal catalysts.

Ozonolysis:

• Unsaturated fatty acids are at a high risk of degradation by ozone.

Circulation of Fatty Acids

Digestion and Intake:

• SCFA and MCFA are absorbed directly into the blood through intestinal capillaries and transported via the hepatic portal vein, similar to other nutrients.
• LCFA are absorbed in the intestine's villi, transformed into triglycerides, then coated with cholesterol and proteins to create chylomicrons.
• Chylomicrons travel through the lymphatic duct to a location near the heart, where they are stored or metabolized for energy.

Metabolism:

• Fatty acids undergo beta-oxidation and the citric acid cycle in mitochondria, breaking down into CO2 and water.
• Energy is released in the form of ATP after oxidative phosphorylation.