Fatty Acids and Lipid Classifications Quiz

Lipid Chemistry

• Lipids are a diverse group of hydrophobic molecules.
• Fatty acids have the general formula C_nH_2n + 1COOH.
• "Free" fatty acids are not attached to other molecules.
• Fatty acids are amphipathic molecules, with a hydrophilic carboxylic group and a hydrophobic aliphatic tail.
• Even-numbered straight-chain fatty acids are prevalent in plants and animals.
• Odd-numbered and branched-chain fatty acids are synthesized by bacteria, contributing to ruminant animal fat.
• Saturated fatty acids have no double bonds in their hydrocarbon chain.
• Unsaturated fatty acids contain one or more double bonds.
• Unsaturated fatty acids can be classified by the degree of unsaturation (monoenoic, dienoic, trienoic).
• Essential fatty acids (EFAs) must be obtained from the diet.
• Unsaturated fatty acids have lower melting points than saturated fatty acids due to cis double bonds disrupting packing.

Saturated Fatty Acids

• Examples include palmitic acid (C16) and stearic acid (C18).
• Common sources include animal and plant fats.

Unsaturated Fatty Acids

• Sources include plant oils like olive oil, flaxseed oil, and others.
• Common examples include oleic acid (monoenoic) and linoleic acid (dienoic).
• Essential fatty acids (EFAs) are unsaturated fatty acids necessary for various bodily functions.
• Polyunsaturated fatty acids (PUFAs) are unsaturated fatty acids with multiple double bonds in their hydrocarbon chain.
• Hydrogenation is a process used to convert unsaturated fatty acids into saturated fatty acids.
• Partial hydrogenation can result in the formation of trans fats.

Chemical Properties of Fatty Acids

• Hydrogenation of unsaturated fatty acids produces saturated fatty acids and can produce trans fats.
• Halogens (Br₂ and I₂) can be added to unsaturated fatty acids at room temperature, in an acetic acid medium.
• This is used in the iodine number determination.
• Fatty acids can be oxidized with ozone to yield a mixture of aldehydes.
• Fatty acids can also be oxidized with KMnO₄ to cleave the molecule at the double bond.
• Oxidation reactions are essential in establishing the position of double bonds.
• Unsaturated fatty acids are more prone to oxidative rancidity, causing off odors and tastes in fats.

Properties of Fatty Acids

• Fatty acids are important energy sources, yielding large amounts of ATP upon metabolism.
• Many cell types utilize glucose or fatty acids for energy, with the heart and skeletal muscle prioritizing fatty acids.
• The body can desaturate fatty acids.

Simple Lipids: Triacylglycerols

• Triacylglycerols are the most abundant lipids, making up 98% of dietary lipids.
• They are major components of fat storage in animals and plants (adipocytes), serving as a concentrated energy store.
• The glycerol backbone is attached to three fatty acid chains via esterification reactions.

Waxes

• Waxes are typically esters of long-chain fatty acids and long-chain alcohols and provide waterproofing.
• Vertebrates secrete waxes to lubricate and waterproof skin.

Compound Lipids

• Phospholipids are the most abundant membrane lipids.
• They have a glycerol backbone esterified to two fatty acids and a phosphate group.
• A polar head group (like choline) is attached to the phosphate group.
• They form bilayers in cell membranes due to their hydrophobic tails and hydrophilic heads.
• Phospholipids assist in the transport of nutrients and waste into and out of cells.

Lecithin

• Lecithin is a phospholipid found in various tissues, particularly in nervous and glandular tissues.
• It helps in the transport and utilization of lipids.
• It plays a role in emulsifying fats in the bloodstream.

Sphingolipids

• Sphingolipids have a sphingosine backbone with fatty acids attached via amide bonds and polar head groups.
• Sphingolipids are essential components of nerve tissues, like myelin sheaths, and may also function in cellular signaling.

Sphingomyelins

• Sphingomyelins are specialized sphingolipids found in myelin sheaths and play a role in electrical signal insulation and transmission.
• A lack of appropriate enzymes to break down sphingomyelins can lead to diseases like Niemann-Pick Disease.

Glycolipids

• Glycolipids comprise lipids that have carbohydrate group attachments.
• Glycolipids are important components of cell membranes, especially critical for the outer surface of nerve cells and chloroplast membranes.
• They form self-sealing lipid bilayers, a fundamental structure in cell membranes.

Derived Lipids: Steroids

• Steroids, like cholesterol, are derived from the basic structure.
• Cholesterol is vital for cell membrane fluidity and is a precursor for many steroids, such as hormones (e.g., testosterone, estrogen) and bile acids.
• cholesterol is an important component of cell membranes and precursor of many other biologically important steroid compounds.
• Lipoproteins transport cholesterol in the bloodstream.

Lipoproteins

• Cholesterol and other lipids are transported in the bloodstream as lipoprotein complexes.
• Different types of lipoproteins exist (HDL, LDL, VLDL, and chylomicrons).
• Different types of lipoproteins have differing roles in transporting lipids and regulating cellular lipid concentrations.

Terpenoids

• Terpenoids are a large group of naturally occurring organic compounds, often found in plants, involved in aromatic qualities, fragrances, medicinal properties.
• Many terpenoids serve as precursors for biologically important compounds such as steroids and other hormones.
• Essential oils are rich in terpenoids.

Eicosanoids

• Eicosanoids are derived from fatty acids and function as hormones, acting as local signals.
• They are involved in complex biological control mechanisms, including inflammation, immune responses, and other important cellular functions.
• Prostaglandins, thromboxanes, and leukotrienes are examples of eicosanoids.
• Eicosanoids are not stored but are rapidly metabolized to inactive products.