Chapter 5 – Lipids
Lipids: a broad range of organic molecules that dissolves easily in organic solvents such as
alcohol, ether or acetone, but are much less soluble in water. Lipids are generally
hydrophobic (averse to water) and lipophilic (soluble in fat and fat solvents). Water-soluble
substances are hydrophilic and lipophobic. The main classes of lipids found in foods and in
the body are triglycerides, phospholipids and sterols. Triglycerides are the largest category of
lipids. In foods, we call lipids “fats and oils”. Phospholipids: compounds that consist of a
glycerol molecule bonded to two fatty acid molecules and to a phosphate group with a
nitrogen-containing component. Phospholipids have both hydrophilic and hydrophobic
regions that make them good emulsifiers. Then are about 2 percent of our dietary lipids and
are found in both plant and animal origin, and the body makes those it needs. These versatile
[=veelzijdig] molecules play crucial roles as a major constituent in cell membranes, and in
blood and body fluids, where they keep fats suspended. Sterols: a category of lipids that
includes cholesterol. Sterols are hydrocarbons with several rings in their structures. Only a
small percentage of our dietary lipids. However, the body makes cholesterol, which is an
important component of cell membranes and a precursor in the synthesis of sex hormones,
adrenal hormones, vitamin D and bile salts.
Lipids share similar functional properties, solubility and transport mechanisms, although the
composition and structure of individual molecules vary. Fatty acids are components of both
triglycerides and phospholipids and are often attached to cholesterol. Fatty acids [= are
compounds containing a long hydrocarbon chain with a carboxyl group (COOH, alpha
carbon) at one end and a methyl group (CH3, omega carbon) at the other end] determine the
characteristics of a fat such as whether it is solid or liquid at room temperature. Fatty acids
differ in chain length, which is the number of carbons that a fatty acid contains. Foods
contain fatty acids with chain lengths of 4 to 24 carbons, and most have an even number of
carbons. Short-chains have fewer than 6 carbons, medium-chain have 6-10 carbons and longer
chain have 12 or more carbons. The shorter, the more liquid (the lower is the melting point),
and also more water-soluble. Saturated fatty acid: a fatty acid completely filled by hydrogen
with all carbons in the chain linked by single bonds. Unsaturated fatty acid: a fatty acid in
which the carbon chain contains one or more double bonds. Monounsaturated fatty acid: a
fatty acid in which the carbon chain contains one double bond. Polyunsaturated fatty acid: a
fatty acid in which the carbon chain contains two or more double bonds. Foods are mostly a
mix of saturated and unsaturated. However, foods rich in unsaturated fatty acids are more
likely to be liquid at room temperature and have lower melting points, while saturated ones
are mostly solid.
Otherwise identical unsaturated fatty acids can exist in different geometric forms, or isomers.
In most naturally occurring unsaturated fatty acids, the hydrogens next to double bonds are on
the same side of the carbon chain, which is called a cis formation. Cis fatty acid: an
unsaturated fatty acid in which the hydrogens surrounding a double bond are on the same side
of the carbon chain, causing a bend in the chain. Most naturally occurring unsaturated fatty
acids are cis fatty acids. If the double bond is altered, moving the hydrogens across from each
other, the formation is called trans and the carbon chain is straighter. There are small amounts
of trans fatty acids [= unsaturated fatty acid in which the hydrogens surrounding a double
Lipids: a broad range of organic molecules that dissolves easily in organic solvents such as
alcohol, ether or acetone, but are much less soluble in water. Lipids are generally
hydrophobic (averse to water) and lipophilic (soluble in fat and fat solvents). Water-soluble
substances are hydrophilic and lipophobic. The main classes of lipids found in foods and in
the body are triglycerides, phospholipids and sterols. Triglycerides are the largest category of
lipids. In foods, we call lipids “fats and oils”. Phospholipids: compounds that consist of a
glycerol molecule bonded to two fatty acid molecules and to a phosphate group with a
nitrogen-containing component. Phospholipids have both hydrophilic and hydrophobic
regions that make them good emulsifiers. Then are about 2 percent of our dietary lipids and
are found in both plant and animal origin, and the body makes those it needs. These versatile
[=veelzijdig] molecules play crucial roles as a major constituent in cell membranes, and in
blood and body fluids, where they keep fats suspended. Sterols: a category of lipids that
includes cholesterol. Sterols are hydrocarbons with several rings in their structures. Only a
small percentage of our dietary lipids. However, the body makes cholesterol, which is an
important component of cell membranes and a precursor in the synthesis of sex hormones,
adrenal hormones, vitamin D and bile salts.
Lipids share similar functional properties, solubility and transport mechanisms, although the
composition and structure of individual molecules vary. Fatty acids are components of both
triglycerides and phospholipids and are often attached to cholesterol. Fatty acids [= are
compounds containing a long hydrocarbon chain with a carboxyl group (COOH, alpha
carbon) at one end and a methyl group (CH3, omega carbon) at the other end] determine the
characteristics of a fat such as whether it is solid or liquid at room temperature. Fatty acids
differ in chain length, which is the number of carbons that a fatty acid contains. Foods
contain fatty acids with chain lengths of 4 to 24 carbons, and most have an even number of
carbons. Short-chains have fewer than 6 carbons, medium-chain have 6-10 carbons and longer
chain have 12 or more carbons. The shorter, the more liquid (the lower is the melting point),
and also more water-soluble. Saturated fatty acid: a fatty acid completely filled by hydrogen
with all carbons in the chain linked by single bonds. Unsaturated fatty acid: a fatty acid in
which the carbon chain contains one or more double bonds. Monounsaturated fatty acid: a
fatty acid in which the carbon chain contains one double bond. Polyunsaturated fatty acid: a
fatty acid in which the carbon chain contains two or more double bonds. Foods are mostly a
mix of saturated and unsaturated. However, foods rich in unsaturated fatty acids are more
likely to be liquid at room temperature and have lower melting points, while saturated ones
are mostly solid.
Otherwise identical unsaturated fatty acids can exist in different geometric forms, or isomers.
In most naturally occurring unsaturated fatty acids, the hydrogens next to double bonds are on
the same side of the carbon chain, which is called a cis formation. Cis fatty acid: an
unsaturated fatty acid in which the hydrogens surrounding a double bond are on the same side
of the carbon chain, causing a bend in the chain. Most naturally occurring unsaturated fatty
acids are cis fatty acids. If the double bond is altered, moving the hydrogens across from each
other, the formation is called trans and the carbon chain is straighter. There are small amounts
of trans fatty acids [= unsaturated fatty acid in which the hydrogens surrounding a double
