lipids Summery and MCQs.

LIPIDS – Easy Summary & Mnemonics What are Lipids? • Organic, water-insoluble molecules • Soluble in organic solvents (e.g., ether, chloroform) • Include: Fats, oils, waxes, phospholipids, steroids Mnemonic: "LOWS" → Lipids are Organic, Water-insoluble, Solvent-soluble Bloor’s Criteria Lipids are: • Insoluble in water • Soluble in non-polar solvents • Include esters of fatty acids & alcohols Classification of Lipids Sajid Afridi Lecturer SHS 1. Simple Lipids • Esters of fatty acids + alcohol Examples: • Fats (Triglycerides) – Glycerol + 3 Fatty Acids • Waxes – Fatty acid + higher alcohol 2. Compound Lipids Contain extra groups like phosphate, nitrogen, carbohydrate Type Example Phospholipids Lecithin, Cephalin Function Cell membranes Type Example Function Glycolipids Cerebrosides, Gangliosides Brain, nerve function Sulpholipids Sulfate-containing Plants, bacteria Lipoproteins HDL, LDL, VLDL Transport of lipids in blood Mnemonic: "Please Give Some Lipids" 3. Derived Lipids Products of hydrolysis of simple or compound lipids Examples: • Fatty acids, Steroids (cholesterol), Glycerol Fatty Acids (FAs) Saturated FA – No double bond e.g., Stearic acid, Palmitic acid Unsaturated FA – 1+ double bond • Mono-unsaturated: Oleic acid • Poly-unsaturated: Linoleic, Linolenic, Arachidonic Mnemonic: "LOLA" – Linoleic, Oleic, Linolenic, Arachidonic Essential Fatty Acids (EFA) Not synthesized by body ➡ Linoleic, Linolenic, Arachidonic Mnemonic: "LLA are Essential" Fatty Acid Naming Term Meaning Δ (delta) Position of double bond ω (omega) Last carbon (CH₃ end) e.g. 18:1 Δ9 = 18 carbon, 1 double bond at 9th position Special Reactions of Unsaturated Fats 1. Hydrogenation → oil → ghee (solid fat) 2. Halogenation → tests unsaturation (iodine number) 3. Oxidation → drying of oils (e.g., linseed oil) Eicosanoids (Local Hormones) Derived from arachidonic acid (20:4) 3 Types: • Prostaglandins (PG) – inflammation • Thromboxanes (TX) – clotting • Leukotrienes (LT) – bronchoconstriction Mnemonic: "PTL from AA (Arachidonic Acid)" Steroids & Cholesterol • Steroids: 4 fused rings • Cholesterol: Precursor for vitamin D, bile salts, sex hormones • Found in cell membranes Mnemonic: "CHOL-DASH" → CHOLesterol → D (vit D), A (Aldosterone), S (Sex hormones), H (HDL/LDL) Vitamin D Synthesis 7-Dehydrocholesterol → (UV light) → Vitamin D3 (Cholecalciferol) → Liver & kidney → Calcitriol Triglycerides (Glycerides) • Mono / Di / Tri-glycerides = Glycerol + 1/2/3 FA • Major energy storage form in adipose tissue • Hydrolysis → glycerol + FA • Saponification → soap formation • Emulsification by bile salts (important for digestion) Mnemonic: “GLY-Tri = Energy” → Glycerol + 3 FA = storage Rancidity & Hydrogenation • Rancidity = bad smell/taste from fat oxidation • Hydrogenation = ↑ shelf life, but creates trans fats Tip: Trans fats = BAD → ↑LDL, ↓HDL → Heart Risk Lipoproteins Type Function Nickname Chylomicrons Transport dietary fat to tissues VLDL Liver → fat to tissues Very Lousy LDL Delivers cholesterol to cells Bad Cholesterol HDL Takes cholesterol back to liver Good Cholesterol Mnemonic: "Lipo Cars: VLDL (to), LDL (bad), HDL (back)" Biological Functions of Lipids Function Examples Energy storage Triglycerides Structure Phospholipids, Cholesterol Insulation/protection Adipose tissue, Myelin Hormone precursor Steroids Vitamin absorption A, D, E, K (fat-soluble) Mnemonic: "LIPID = Layers, Insulation, Precursors, Insoluble, Dense energy" 1. Lipids are soluble in: a) Water b) Alcohol c) Ether d) None 2. Which of the following is a simple lipid? a) Phospholipid b) Triglyceride c) Glycolipid d) Lipoprotein 3. Waxes are esters of fatty acids with: a) Glycerol b) Steroids c) Higher alcohols d) Sugars 4. Which is a compound lipid? a) Phospholipid b) Triglyceride c) Glycerol d) Waxes 5. Lecithin is an example of: a) Phospholipid b) Sterol c) Glycolipid d) Sphingolipid 6. Cerebrosides are: a) Phospholipids b) Glycolipids c) Steroids d) Proteins 7. Which of the following is a derived lipid? a) Lecithin b) Cholesterol c) Triglyceride d) Phosphatidylserine 8. Saturated fatty acids contain: a) One double bond b) No double bonds c) Two double bonds d) Aromatic rings 9. Oleic acid is: a) Saturated b) Monounsaturated c) Polyunsaturated d) Aromatic 10. Arachidonic acid is a: a) Saturated fatty acid b) Monounsaturated c) Polyunsaturated fatty acid d) Wax 11. Essential fatty acids include: a) Stearic acid b) Linoleic acid c) Palmitic acid d) Oleic acid 12. Which is not an essential fatty acid? a) Oleic acid b) Linoleic acid c) Linolenic acid d) Arachidonic acid 13. Double bond in fatty acids is denoted by: a) @ b) Δ c) π d) Ω 14. Omega-3 fatty acid has double bond at: a) C2 b) C3 c) C4 d) C5 15. Hydrogenation of oils leads to: a) Hardening b) Oxidation c) Saponification d) Melting 16. Iodine number indicates: a) Degree of unsaturation b) Molecular weight c) Saponification index d) Oxidation potential 17. DHA is mainly present in: a) Kidney b) Liver c) Retina and brain d) Bone 18. Which is the structural unit of steroids? a) Cyclopentanoperhydrophenanthrene b) Benzene ring c) Pyrrole ring d) Imidazole ring 19. Cholesterol is a: a) Glycolipid b) Wax c) Sterol d) Phospholipid 20. Vitamin D3 is synthesized from: a) 7-dehydrocholesterol b) Cholesterol c) Lecithin d) Squalene 21. Triglycerides are esters of glycerol and: a) Amino acids b) Fatty acids c) Cholesterol d) Steroids 22. Glycerol is a: a) Di-alcohol b) Trihydric alcohol c) Ketone d) Fatty acid 23. Phosphoglycerides are important in: a) Hormone production b) Membrane structure c) DNA repair d) Bile salt formation 24. Lecithins contain: a) Ethanolamine b) Choline c) Galactose d) Serine 25. Lipids forming micelles in blood: a) Phospholipids b) Cholesterol c) Triglycerides d) Steroids 26. Lipids involved in nerve conduction are: a) Sphingomyelins b) Triglycerides c) Steroids d) Waxes 27. Glycosphingolipids with a single sugar are: a) Cerebrosides b) Gangliosides c) Lecithins d) Sulpholipids 28. Eicosanoids are derived from: a) Arachidonic acid b) DHA c) Stearic acid d) Cholesterol 29. Prostaglandins belong to: a) Eicosanoids b) Steroids c) Glycolipids d) Fatty acids 30. Prostaglandin E2 is involved in: a) Inflammation b) Coagulation c) Digestion d) Metabolism 31. Thromboxane A2 causes: a) Platelet aggregation b) Vasodilation c) Anticoagulation d) Lipid storage 32. Lipids act as: a) Local hormones (e.g., prostaglandins) b) Long-acting hormones c) Neurotransmitters d) Enzymes 33. Drying of oils is due to: a) Halogenation b) Oxidation c) Hydrolysis d) Hydrogenation 34. Which of the following acts as emulsifier in digestion? a) Bile salts b) Phospholipids c) Lecithin d) Lipase 35. Saponification produces: a) Alcohol and water b) Soap and glycerol c) Acetyl-CoA d) Detergents 36. Which of the following causes rancidity of fats? a) Oxidation b) Hydrolysis c) Emulsification d) Hydrogenation 37. Trans fats are produced during: a) Partial hydrogenation b) Hydrolysis c) Oxidation d) Saponification 38. Trans fats increase risk of: a) Liver cirrhosis b) Coronary heart disease c) Osteoporosis d) Hypoglycemia 39. Which is considered "bad cholesterol"? a) LDL b) HDL c) VLDL d) Chylomicrons 40. Which lipoprotein collects cholesterol from tissues? a) LDL b) HDL c) VLDL d) IDL 41. Lipoprotein with highest lipid content: a) Chylomicrons b) LDL c) HDL d) IDL 42. Major storage form of energy in body: a) Glycogen b) Triglycerides c) Cholesterol d) Phospholipids 43. Lipids provide how many kcal/g? a) 4 b) 9 c) 6 d) 2 44. Vitamin A, D, E, K are: a) Water-soluble b) Fat-soluble c) Semi-soluble d) Insoluble 45. Which fatty acid is most present in the brain? a) Linoleic acid b) DHA c) Stearic acid d) Oleic acid 46. Which lipid protects internal organs? a) Adipose tissue (fats) b) Phospholipids c) Cholesterol d) Glycolipids 47. Which of these is NOT a phosphoglyceride? a) Cephalin b) Lecithin c) Cholesterol d) Cardiolipin 48. LDL transports: a) Cholesterol from liver to tissues b) Fatty acids to liver c) Glucose to cells d) Oxygen 49. Which enzyme breaks down fats? a) Amylase b) Lipase c) Trypsin d) Maltase 50. Ergosterol converts to Vitamin D2 in: a) Skin b) Yeast (UV exposure) c) Liver d) Kidney !