Notes on Lipids and Fats PDF

Notes on Lipids 1. Overview of Lipids: Lipids are a diverse group of macromolecules, including fats, waxes, oils, steroids, and phospholipids. They are made up of long hydrocarbon chains, consisting exclusively of hydrogen and carbon. Due to their hydrocarbo...

Notes on Lipids 1. Overview of Lipids: Lipids are a diverse group of macromolecules, including fats, waxes, oils, steroids, and phospholipids. They are made up of long hydrocarbon chains, consisting exclusively of hydrogen and carbon. Due to their hydrocarbon structure, lipids are non-polar and insoluble in water. 2. Fatty Acids and Triglycerides: Fatty Acids: Basic building blocks of certain lipids. They can be saturated, unsaturated, trans fats, or omega fatty acids. Triglycerides: Formed from three fatty acids bonded to a glycerol molecule. They are important for energy storage in the form of body fat (adipose tissue). 3. Phospholipids: Consist of two non-polar fatty acid tails attached to a polar phosphoglyceraldehyde head. They are crucial in forming the phospholipid bilayer of cell membranes, which protects cells and controls what enters and exits. 4. Steroids: Unlike other lipids, steroids do not contain fatty acids but are formed from four linked cyclic rings. Examples include cholesterol, cortisol, and hormone steroids like progesterone and testosterone. They are hydrophobic and not water-soluble. 5. Waxes: Have unique structures and are found in bird feathers and plant leaves. They provide waterproofing properties, causing water to bead up and run off surfaces like leaves. Notes on Fats 1. Role and Importance of Fats: Essential for a healthy diet, contributing to taste and texture in foods. Major energy source, critical component of cells and tissues, and help in absorbing essential vitamins. Can be converted into other molecules like prostaglandins, aiding cell communication. 2. Structure of Fats: Fats have a three-carbon backbone called glycerol, and fatty acid chains made of carbon and hydrogen atoms. When an “OH” from glycerol binds with an “H” from a fatty acid, a water molecule (H₂O) is released, forming a bond: ○ Monoglyceride: One bond formed. ○ Diglyceride: Two bonds formed. ○ Triglyceride: Three bonds formed. 3. Types of Fatty Acids: By Chain Length: ○ Short-Chain: 2-5 carbons. ○ Medium-Chain: 6-12 carbons. ○ Long-Chain: 13 or more carbons. ○ By Bond Type: ○ Saturated Fatty Acids: Only single bonds between carbons; fully saturated with hydrogen, resulting in straight chains. Typically solid at room temperature. ○ ○ Unsaturated Fatty Acids: One or more double bonds, causing kinks in the chain. Liquid at room temperature due to inability to pack tightly. ○ ○ Monounsaturated Fatty Acids: One double bond. ○ ○ Polyunsaturated Fatty Acids: Two or more double bonds. 4. Classification by Location of Double Bonds: Omega-3 Fatty Acids: First double bond is three carbons from the omega (methyl) end. ○ Found in marine sources like fish (EPA, DHA) and plant sources like flaxseed (ALA).  ○ Omega-6 Fatty Acids: First double bond is six carbons from the omega end. ○ Found in oils (safflower, corn) and animal sources (arachidonic acid). ○ Omega-9 Fatty Acids: First double bond is nine carbons from the omega end. ○ Found in olive oil, canola oil, and almonds. ○ 5. Cis vs. Trans Configurations: Cis Configuration: Functional groups on the same side of the double bond; causes the molecule to bend, making it more fluid (e.g., cooking oils). Trans Configuration: Functional groups on opposite sides of the double bond, resulting in straight chains and tighter packing. Trans Fats: Created through partial hydrogenation. Found naturally in some animal products and previously used in food products, but largely removed due to health risks. 6. Digestion and Absorption of Fats: Triglycerides form large fat globules due to their hydrophobic nature. Enzymes called lipases break down triglycerides into monoglycerides and free fatty acids. Bile salts emulsify large fat droplets into smaller ones, increasing surface area for lipase action. Monoglycerides and fatty acids form micelles, which are absorbed by intestinal cells (enterocytes). Inside enterocytes, reassembled into triglycerides and packed into chylomicrons (lipoproteins) for transport in the lymph and blood. 7. Health Benefits and Recommendations: Polyunsaturated fats reduce LDL cholesterol and lower cardiovascular disease risk. Omega-3 fatty acids (DHA, EPA) lower triglycerides and support brain and eye development in infants. Saturated fats should be consumed in limited amounts due to potential cardiovascular health risks.  Replacing saturated fats with polyunsaturated fats is beneficial, while replacing them with refined carbohydrates is not. Recommended daily intake: 20-35% of total calories from fats (44-78 grams for a 2000-calorie diet). Less than 10% of daily calories should come from saturated fats; trans fats should be minimized.