Week 3 – Lipids
Dietary lipids consist of:
- Triglycerides (=triacylglycerol)
3 fatty acids which may differ, and 1 glycerol molecule
The fatty acids can differ in:
o Chain length
o Degree of saturation
Saturated fatty acid
Monounsaturated fatty acid
Polyunsaturated fatty acid
o Point of saturation
Nomenclature fatty acids 20:4 n/6
This means: 20 carbon atoms, 4 double bonds, n/6 is the position of double bonds.
n/-designation: counts from the methyl end first double bond starts after 6 carbons
-designation: counts from carboxyl end indicates the position of all double bonds
Most abundant fatty acids in human diet:
o Palmitic acid – C16:0
o Stearic acid – C18:0
o Oleic acid – C18:1
o Linoleic acid – C18:2
o Linolenic acid – C18:3
Palmitic and oleic acid are the most common in peoples diet.
Fatty acids with an odd number of carbon atoms are relatively rare in mammals.
Firmness of fat is determined by types of fatty acids. A shorter fatty acid results in a lower
melting point, and also the more unsaturated fatty acid results in a lower melting point.
Triglycerides containing mostly saturated fatty acids are chemically more stable. They are less
prone to oxidation, which impacts the properties negatively.
Hydrogenation:
Process in which unsaturated fatty acids are
converted into saturated fatty acids.
Hydrogenation make the oil more stable and less prone to spoilage. It also leads to conversion
of the cis-fatty acids naturally present, into trans-fatty acids. The trans-fatty acids have a
negative influence on health.
The double bonds are naturally present in foods in the cis configuration. This gives a kink in
the molecular shape.
The trans configuration results in a more linear fatty acid. Trans fatty acids are formed during
industrial processing of oils. The exception is conjugated linoleic acid (CLA), a trans fatty
acid present in dairy.
, - Phospholipids
They contain:
o Diglyceride
o Phosphate group
o Simple organic molecule such
as choline
They have a polar and apolar side
(amphipathic).
Roles of phospholipids:
o Plasma membrane
o Emulsifiers forming a
bilayer which functions as a barrier for entry of numerous molecules into the
cell.
- Sterols
o Cholesterol (animal)
o Plant sterols/ stanols
Plant sterols are cholesterol look-a-likes
they differ at one branch point.
Only small amounts of plant sterols are
absorbed, but most will leave the body via
the stools.
Plant sterols inhibit cholesterol absorption
and cholesterol levels in the blood to a
maximum of 10%.
Examples of plant sterols: sitosterol, campesterol and stigmasterol
Some major fats and oils compostions:
- Lard/butter: rich in saturated fatty acids
- Vegetable oils: mostly unsaturated fatty acids
- Coconut oil (exception): very rich in medium chain fatty acids, 8 to 12.
- Soybean oil is very rich in linoleic acid (C18:3)
- Fish oil provides a lot fatty acids with 20 to 22 carbons, and typically (C20:5 and
C22:6)
Digestion of fat:
1. Possible fat digestion as part of fat tasting (salivary glands produce lipase called
lingual lipase same lipase as gastric lipase)
2. Minor fat digestion in the stomach by gastric lipase
3. Bile acids stored in gall bladder assist with fat digestion
4. Major fat digestion in the small intestine by pancreatic lipase (produced by pancreas)
5. No digestion of gat in the colon
Dietary lipids consist of:
- Triglycerides (=triacylglycerol)
3 fatty acids which may differ, and 1 glycerol molecule
The fatty acids can differ in:
o Chain length
o Degree of saturation
Saturated fatty acid
Monounsaturated fatty acid
Polyunsaturated fatty acid
o Point of saturation
Nomenclature fatty acids 20:4 n/6
This means: 20 carbon atoms, 4 double bonds, n/6 is the position of double bonds.
n/-designation: counts from the methyl end first double bond starts after 6 carbons
-designation: counts from carboxyl end indicates the position of all double bonds
Most abundant fatty acids in human diet:
o Palmitic acid – C16:0
o Stearic acid – C18:0
o Oleic acid – C18:1
o Linoleic acid – C18:2
o Linolenic acid – C18:3
Palmitic and oleic acid are the most common in peoples diet.
Fatty acids with an odd number of carbon atoms are relatively rare in mammals.
Firmness of fat is determined by types of fatty acids. A shorter fatty acid results in a lower
melting point, and also the more unsaturated fatty acid results in a lower melting point.
Triglycerides containing mostly saturated fatty acids are chemically more stable. They are less
prone to oxidation, which impacts the properties negatively.
Hydrogenation:
Process in which unsaturated fatty acids are
converted into saturated fatty acids.
Hydrogenation make the oil more stable and less prone to spoilage. It also leads to conversion
of the cis-fatty acids naturally present, into trans-fatty acids. The trans-fatty acids have a
negative influence on health.
The double bonds are naturally present in foods in the cis configuration. This gives a kink in
the molecular shape.
The trans configuration results in a more linear fatty acid. Trans fatty acids are formed during
industrial processing of oils. The exception is conjugated linoleic acid (CLA), a trans fatty
acid present in dairy.
, - Phospholipids
They contain:
o Diglyceride
o Phosphate group
o Simple organic molecule such
as choline
They have a polar and apolar side
(amphipathic).
Roles of phospholipids:
o Plasma membrane
o Emulsifiers forming a
bilayer which functions as a barrier for entry of numerous molecules into the
cell.
- Sterols
o Cholesterol (animal)
o Plant sterols/ stanols
Plant sterols are cholesterol look-a-likes
they differ at one branch point.
Only small amounts of plant sterols are
absorbed, but most will leave the body via
the stools.
Plant sterols inhibit cholesterol absorption
and cholesterol levels in the blood to a
maximum of 10%.
Examples of plant sterols: sitosterol, campesterol and stigmasterol
Some major fats and oils compostions:
- Lard/butter: rich in saturated fatty acids
- Vegetable oils: mostly unsaturated fatty acids
- Coconut oil (exception): very rich in medium chain fatty acids, 8 to 12.
- Soybean oil is very rich in linoleic acid (C18:3)
- Fish oil provides a lot fatty acids with 20 to 22 carbons, and typically (C20:5 and
C22:6)
Digestion of fat:
1. Possible fat digestion as part of fat tasting (salivary glands produce lipase called
lingual lipase same lipase as gastric lipase)
2. Minor fat digestion in the stomach by gastric lipase
3. Bile acids stored in gall bladder assist with fat digestion
4. Major fat digestion in the small intestine by pancreatic lipase (produced by pancreas)
5. No digestion of gat in the colon
