Lesson 7

• Lipids are a class of macromolecules that are nonpolar and hydrophobic in nature
• Fats and oils are types of lipids that serve as a stored form of energy
• Waxes are a type of lipid
• Phospholipids are lipids that make up the matrix of membranes
• Steroids are another class of lipids with a basic structure of four fused carbon rings
• Cholesterol is a type of steroid that is an important constituent of the plasma membrane and precursor of steroid hormones
• Lipids are a chemically heterogeneous group of compounds that are insoluble in water but soluble in non-polar solvents, such as hexane and chloroform
• Structural lipids serve as components of the structure in animals and plants, found in the form of meat and vegetables, respectively
• Storage fats occur in milk, adipose tissue of farm animals, and seed oils, providing over twice as much energy per unit weight as proteins or carbohydrates
• Anhydrous refers to the non-polar nature of lipids, which lack water molecules and contain more energy than carbohydrates
• Palatability is the quality of being pleasant to eat, significantly contributed by the presence of lipids in the diet
• Essential fatty acids are fatty acids that are not synthesized in human beings but are necessary for growth
• Fat-soluble vitamins A, D, E, and K require lipids for effective absorption from the intestine
• Many enzymes require lipid molecules for maximal activity
• Simple lipids are esters of fatty acids with glycerol and monohydric alcohols
• Fats are esters of fatty acids with glycerol, also known as triacylglycerols
• Examples of fats include vegetable oils (from plants) and ghee/butter (from animals)
• Oils are a subcategory of simple lipids that are liquid at room temperature
• Waxes are esters of fatty acids and alcohols other than glycerol
• Examples of waxes include carnauba wax (from plants), beeswax (from insects), and lanolin (from animals)
• Compound lipids are esters containing chemical groups in addition to alcohol and fatty acids
• Phospholipids are compound lipids that contain a phosphate group
• Phospholipids are further classified as glycerophospholipids (if the alcohol is glycerol) or sphingophospholipids (if the alcohol is sphingosine)
• Glycolipids are compound lipids that contain hexose units, preferably galactose, along with fatty acids and alcohol
• An example of glycolipids is cerebrosides
• Sulpholipids are compound lipids found in plants that contain sulfated hexose with fatty acids and alcohol
• Lipoproteins are compound lipids that contain protein subunits along with lipids
• Lipoproteins are further classified based on density and lipid composition as VLDL, LDL, and HDL
• Derived lipids are substances formed from the breakdown of alcohols, fatty acids, aldehydes, ketones, sterols, and hydrocarbons found in simple and compound lipids through hydrolysis
• Fatty acids are long chain carboxylic acids synthesized by the condensation and reduction of acetyl coenzyme-A units by fatty acid synthase
• Saturated fatty acids have no double bonds, examples include stearic and palmitic acids
• Monounsaturated fatty acids have one double bond, an example is oleic acid
• Polyunsaturated fatty acids have multiple double bonds, examples include linoleic and linolenic acids
• Cis (E) fatty acids are common fatty acids with double bonds in the cis configuration
• Membrane fluidity is the tendency of unsaturated fatty acids to remain in a liquid state at room temperature, allowing for flexibility in cell membranes
• Thermoregulation is the ability of organisms to regulate their internal body temperature
• Cold adaptation involves the use of more unsaturated fatty acids in cell membranes by bacteria and plants exposed to cold temperatures to maintain membrane fluidity
• Delta system:

  • Assigns numbers to double bonds in acids starting from the carboxyl group (Δ carbon)
• Omega system:

  • Indicates the position of the first double bond in acids counting from the opposite end of the molecule (ω carbon)
• Essential Fatty Acids:

  • Not synthesized in the body but required for normal body growth and maintenance
  • Must be obtained through diet