Lipids: Fatty Acids, Triglycerides, and More PDF

Fatty Acids: They are lipids with long chains of carbon and hydrogen. End with a carboxylic acid group. Hydrophobic: They do not mix with water (water-fearing). Types of Fatty Acids: Saturated Fatty Acids: ○ Only have single bonds in the hydrocarbon chain....

Fatty Acids: They are lipids with long chains of carbon and hydrogen. End with a carboxylic acid group. Hydrophobic: They do not mix with water (water-fearing). Types of Fatty Acids: Saturated Fatty Acids: ○ Only have single bonds in the hydrocarbon chain. ○ Have the maximum number of hydrogen atoms. ○ Straight and flexible structure. ○ Typically solid at room temperature. Unsaturated Fatty Acids: ○ Contain at least one double bond in the hydrocarbon chain. ○ Have fewer hydrogen atoms. ○ Have “kinks” in their structure due to double bonds. ○ Typically liquid at room temperature. Triacylglycerol (Triglyceride): Formed by linking three fatty acids to a glycerol molecule. Main component of body fat (adipose tissue). Major part of skin oils (sebum). Serve as efficient energy-storage molecules, providing more than double the calories of carbohydrates and proteins. Triglycerides: Simple lipids made from glycerol and fatty acids. Complex Lipids: Contain additional components (e.g., phosphate in phospholipids, carbohydrates in glycolipids). Phospholipid Structure: Composed of two fatty acids linked to glycerol (diglyceride). One binding position on glycerol is occupied by a phosphate group instead of another fatty acid. Fatty acid chains can be saturated, unsaturated, or a mix. Hydrophobic vs. Hydrophilic:  Triglycerides: Nonpolar (hydrophobic) due to long hydrocarbon chains; do not mix well with water. Phospholipids: Have a negatively charged phosphate group, making them polar (hydrophilic) and attracted to water. Amphipathic Nature: Phospholipids have both hydrophobic tails (nonpolar) and hydrophilic heads (polar). The polar "head" is attracted to water; the nonpolar "tails" are not. Micelles and Lipid Bilayers: Micelles: Spherical structures with hydrophobic tails inside and polar heads outside. Lipid Bilayers: Formed by tail-to-tail arrangement of phospholipids; make up cell membranes and many intracellular structures. Function: These structures are crucial for cell membranes and various physiological functions (e.g., vesicles and liposomes). Isoprenoids (Terpenoids): Definition: Branched lipids formed from chemical changes to isoprene. Roles: ○ In Plants and Animals: Various physiological functions. ○ Technological Uses: Pharmaceuticals (e.g., capsaicin). Pigments (e.g., beta carotene, xanthophylls). Fragrances (e.g., menthol, camphor, limonene, pinene). Long-Chain Isoprenoids: Found in oils and waxes. ○ Waxes: Water-resistant and hard at room temperature. Soften when heated. ○ In Humans: Produced in sebaceous glands as sebum (contains triacylglycerol, wax esters, squalene). ○ Skin Bacteria: Feed on these lipids, e.g., Cutibacterium acnes generates fatty acids and is linked to acne. Steroids: Definition: Complex, ringed structures found in cell membranes; some act as hormones. Sterols: ○ Definition: A type of steroid with an OH group. ○ Characteristics: Mostly hydrophobic but have hydrophilic hydroxyl groups. ○ Common Sterol: Cholesterol.  Structure: Four rings with a double bond and a hydroxyl group. Function: Strengthens cell membranes in eukaryotes and some bacteria (e.g., Mycoplasma). Prokaryotes: Generally do not produce cholesterol but have similar compounds (hopanoids) that strengthen membranes. Fungi and Protozoa: Produce ergosterol, which also strengthens cell membranes.