Overview
This lecture explains in detail the structure, types, functions, and importance of fats (lipids) and nucleic acids (DNA, RNA) under biomolecules.
Fats (Lipids)
- Fats are also called lipids; they serve as energy storage, structural components, and insulation.
- Fats mainly consist of glycerol (alcohol) and fatty acids.
- The general formula of fatty acids: Cn H2n O2.
- One glycerol can bind with 1, 2, or 3 fatty acids, forming: mono-, di-, triglycerides.
- Triglyceride is called true fat.
- An ester bond forms between glycerol and fatty acids, releasing water.
- Fatty acids without double bonds are saturated, with double bonds are unsaturated (oils).
- Saturated fats (ghee, butter) come from animal sources, unsaturated (oils) from plant sources.
- Unsaturated fatty acids: mono (MUFA), poly (PUFA); they are healthy.
- Two types of fatty acids in the body: essential (linoleic, linolenic, arachidonic - 'red'), non-essential.
- LDL (low-density lipoprotein) is called "bad", HDL (high-density) "good" cholesterol.
Nucleic Acids (DNA and RNA)
- Nucleic acids: genetic material; two types - DNA and RNA.
- DNA was discovered by Friedrich Miescher (nuclein), renamed by Richard Altmann.
- DNA structure is a double helix (Watson & Crick, 1953), made of two anti-parallel strands.
- DNA's monomer (unit): nucleotide (sugar + nitrogen base + phosphate).
- Sugar: deoxyribose (DNA), ribose (RNA).
- DNA bases: adenine (A), guanine (G), cytosine (C), thymine (T); in RNA, thymine is replaced by uracil (U).
- Phosphodiester bond between two nucleotides; hydrogen bonds between two strands (A=T, 2 bonds; GтЙбC, 3 bonds).
- Purines: A, G; Pyrimidines: C, T, U.
- DNA is a right-handed double helix, B-form is common; 10 base pairs per helical turn (3.4 nm).
- Chargaff's rule: A=T, G=C; species-specific ratio.
- DNA packaging - nucleosomes formed with histone proteins.
Key Terms & Definitions
- Glycerol тАФ a simple alcohol, part of fats.
- Fatty acid тАФ a compound with a hydrocarbon chain and acidic nature.
- Ester bond тАФ bond formed between glycerol and fatty acids.
- Monoglyceride/Diglyceride/Triglyceride тАФ fats with 1/2/3 fatty acids attached to glycerol.
- Saturated fats тАФ fatty acids without double bonds; solid form.
- Unsaturated fats тАФ with double bonds; liquid state.
- LDL/HDL тАФ lipoproteins that carry cholesterol.
- Nucleotide тАФ combination of sugar + nitrogen base + phosphate.
- Phosphodiester bond тАФ bond connecting two nucleotides.
- Histone тАФ protein aiding DNA packaging.
- Purine/Pyrimidine тАФ two categories of nitrogen bases.
Action Items / Next Steps
- Homework: derive the molecular formula of palmitic and stearic acid from the general formula.
- For the next lesson: study carbohydrates and enzymes.