Lipids

• Lipids are macromolecules containing carbon, hydrogen, and oxygen atoms, with a lower proportion of oxygen compared to carbohydrates
• Triglycerides, the main component of fats and oils, are non-polar, hydrophobic molecules composed of glycerol and fatty acids
• Fatty acids can vary in length and saturation, with saturated fatty acids mainly found in animal fat and unsaturated fatty acids mainly in vegetable oils
• Unsaturated fatty acids can be mono or polyunsaturated, with cis-fatty acids metabolized by enzymes and trans-fatty acids linked with coronary heart disease
• Triglycerides are formed by esterification, where an ester bond forms between glycerol and fatty acids, releasing water molecules in a condensation reaction
• Triglycerides function as energy storage, insulation, buoyancy, and protection in organisms
• Phospholipids, a type of lipid, have a phosphate head (hydrophilic) and fatty acid tails (hydrophobic), making them amphipathic and the main components of cell membranes
• Phospholipids are amphipathic, having both hydrophobic and hydrophilic parts
• Phospholipid molecules form monolayers or bilayers in water due to their hydrophobic and hydrophilic parts
• Phospholipids are the main component (building block) of cell membranes
• When a phospholipid bilayer forms, the presence of hydrophobic fatty acid tails creates a hydrophobic core, acting as a barrier to water-soluble molecules
• The hydrophilic phosphate heads of phospholipids form hydrogen bonds with water, allowing the cell membrane to compartmentalize and organize specific roles into organelles for efficiency
• The composition of phospholipids contributes to the fluidity of the cell membrane:

  • Mainly saturated fatty acid tails result in a less fluid membrane
  • Mainly unsaturated fatty acid tails result in a more fluid membrane
• Phospholipids control membrane protein orientation through weak hydrophobic interactions that hold the proteins within the membrane but still allow movement within the layer
• Triglycerides, a form of lipid, consist of one molecule of glycerol with three fatty acids attached to it
• Saturated fatty acids have single bonds between carbon atoms in the hydrocarbon tail, making them 'saturated' with hydrogen
• Triglycerides are mainly used as energy storage molecules due to the large amounts of chemical energy in their fatty acid tails
• Triglycerides form insoluble droplets inside cells, with hydrophobic fatty acids on the inside and glycerol molecules on the outside
• Phospholipids, another type of lipid, have a phosphate group replacing one of the three fatty acid molecules attached to glycerol, making them suitable for making up the bilayer of cell membranes
• Phospholipids have hydrophilic phosphate groups and hydrophobic fatty acids, allowing them to form a bilayer with the fatty acids facing inwards and the phosphate groups facing outwards, creating a barrier that controls what substances enter and leave the cell