Lipids

• Lipids are a group of macromolecules that contain carbon, hydrogen, and oxygen, but have relatively fewer oxygen atoms than carbohydrates
• Lipids play important roles in energy storage, insulation, and cell membrane structure
• Lipids are non-polar molecules that dissolve well in nonpolar solvents but not in water
• Categories of lipids include fats, oils, waxes, and steroids
• Lipids can be transported in the body through lipoproteins, where digested fats are packaged within a protein coat to make them water-soluble
• Triglycerides contain one glycerol molecule and three fatty acid molecules
• Fatty acids have an unbranched chain of carbon atoms with a carboxyl group at one end and a methyl group at the other end
• Triglycerides are formed from condensation reactions of glycerol and fatty acids
• Fatty acids can be saturated, monounsaturated, or polyunsaturated
• Saturated fatty acids have no double bonds, pack tightly together, and are solid at room temperature
• Monounsaturated fatty acids have one double bond, resulting in a liquid state at room temperature
• Polyunsaturated fatty acids have two or more double bonds, also resulting in a liquid state at room temperature
• Cis and trans configurations describe the arrangement of atoms around double bonds in unsaturated fatty acids
• Triglycerides containing monounsaturated or polyunsaturated fatty acids have lower melting points and are liquids at room temperature
• Triglycerides in adipose tissue are used for energy storage and thermal insulation in animals
• Steroids are a group of lipids that can pass through the phospholipid bilayer due to their hydrophobic nature
• Steroids like oestradiol and testosterone play key roles in reproductive development
• Different steroid molecules vary based on the addition and placement of functional groups
• Cholesterol acts as a modulator of membrane fluidity in the phospholipid bilayer
• Steroids diffuse directly through the hydrophobic core of the phospholipid bilayer