Lipids & nucleic acid

Fatty Acids and Lipids

• Composition

  • Mainly composed of carbon (C) and hydrogen (H).

  • Includes some oxygen (O) atoms.

  • Soluble in non-polar solvents, making them hydrophobic (water-repelling).

• Fats are metabolized twice as much as carbs

• carbs and proteins with the help of enzymes can turn into fat.

• Structure

  • Saturated vs. Unsaturated Fatty Acids:

    • Saturated fatty acids have no double bonds between carbon atoms, allowing for a straight structure that can pack tightly.

    • Unsaturated fatty acids (with one or more double bonds) introduce bends in the molecule, making them less tightly packed.

      • Example: Monounsaturated fatty acids have one double bond.

      • Example: Polyunsaturated fatty acids (like linoleic acid) have two double bonds.

• Health Implications

  • Unsaturated fatty acids are beneficial because they:

    • Increase fluidity of lipids.

    • Help decrease fat deposits in arteries, reducing cardiovascular risks.

    • Provide twice the energy yield compared to carbohydrates.

Phospholipids and Membrane Structure

• Phospholipid Composition

  • Composed of glycerol, two fatty acids, and a phosphate group.

  • Amphipathic lipid

  • Fatty acids are hydrophobic, while the phosphate head is hydrophilic (water-attracting).

  • Phosphatidylcholine is a common phospholipid found in cell membranes, consisting of glycerol, two fatty acids, and a choline head group.

• Biological Membranes

  • Phospholipids arrange themselves in bilayers with hydrophilic heads facing outward and hydrophobic tails facing inward.

  • This bilayer structure forms the foundation of all biological membranes, contributing to membrane fluidity and functionality.

  • Membrane properties vary depending on saturation levels of fatty acids.

Role of Cholesterol and Other Lipids

• Cholesterol Functions

  • Integral to cell membranes, impacting fluidity and stability.

  • Precursor for steroid hormone synthesis.

  • Excess cholesterol is excreted from the body via bile salts.

• Plant and Skin Oils

  • Oils prevent water loss from leaves and maintain skin moisture and suppleness.

• Carotenoids

  • consists of isoprene units which converts to vitamin A

Nucleic Acids

• Functions

  • Serve as genetic material (DNA) and messenger molecules (RNA).

  • DNA provides hereditary information, and mutations can occur during replication.

  • RNA is synthesized from DNA as a temporary copy (transcription) that moves to the cytoplasm for protein synthesis (translation).

• Structure of Nucleotides

  • Composed of a sugar (ribose or deoxyribose), a phosphate group, and nitrogenous bases.

  • Different bases result in DNA (A, T, C, G) and RNA (A, U, C, G).

Transcription and Translation Process

• Transcription (Inside the Nucleus)

  • RNA polymerase binds to specific gene sequences to synthesize messenger RNA (mRNA).

  • mRNA represents a copy of the gene that can be transported to ribosomes.

• Translation (In the Cytoplasm)

  • Ribosomes read mRNA sequences, translating them into polypeptide chains (proteins).

  • The start codon (AUG) signals the ribosome to begin translation.

ATP and Cellular Signaling

• Role of ATP

  • Serves as a primary energy source for cellular processes.

  • Produced through various metabolic pathways.

• Cell Signaling Mechanism

  • Hormones bind to membrane receptors, triggering intracellular signaling pathways involving G-proteins, which activate additional enzymes (e.g., adenylate cyclase).

  • Cyclic AMP (cAMP) acts as a second messenger, facilitating communication within the cell.