NUTR 3210 Lecture Notes - Lecture 6: Lipolysis, Caffeine, Hepatocyte
27 Jun 2018
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Learning outcomes
Describe the classification and structure of lipids
Describe the digestion and absorption of dietary lipids
Describe the function of dietary lipids in the human body
Describe the metabolism of dietary lipids, and predict how metabolism would change under
different conditions
Describe the impact of essential dietary lipids on human health
Apply principles of nomenclature to novel lipid structures
Introduction to lipids
Quick facts:
oSoluble in organic solvents
oWide variety of structures and functions
oSources of energy and storage
oBuilding blocks of biological membranes
The general chemistry of lipids allows them to be extracted from tissues with a non-polar
solvent such as ether, which will extract neutral lipids like triglycerides; or by using a mixture of
chloroform and methanol, which will dissolve phospholipids in addition to neutral lipids
Metabolically speaking, lipids are a source of energy and have roles in signalling, as precursors
for hormones and eicosanoids
Other important roles include being components of cell and organelle membranes
Most of the lipids are built on fatty acids, while some have a sterol, or cholesterol base
Fatty acids
Quick facts:
oChains of 2 to 24 carbons
oThe general formula has an R that can be a long linear carbon-hydrogen chain
oThere are two categories - saturated and unsaturated
Saturated: with maximum number of H per C atoms; only single bonds
Unsaturated: have missing H atoms per C: with double bonds (C=C), they can be
monounsaturated (MUFA) and polyunsaturated (PUFA)
From the general formula, we will see that fatty acids have a long hydrogen-saturated portion of
the molecule (R), where most of the energy content is found and there is very little oxygen
present
fatty acids molecules have two zones, one hydrophobic and one hydrophilic - a single molecule
has interesting properties, ranging from amphipathic to detergent-like in nature
oAn amphipathic molecule has a weaker hydrophilic zone, so it can form organized
structures that form an interface between water and lipids
Membrane bilayers are similar, except the inner core is generated by the inside
of each membrane leaflet
In cases where the hydrophilic zone is very strong, the molecules can have detergent like
characteristics, which will disturb and destruct lipid structures into smaller droplets to form
emulsions - detergent activity will disturb cellular systems
As the amount of free fatty acids build up, they will act as detergents and can emulsify and
destroy plasma membranes
In metabolism, we can see a fairly strict limitation on free fatty acids built up in systems to avoid
toxic effects
find more resources at oneclass.com
find more resources at oneclass.com
Free fatty acids are released from lipids during digestion to aid in emulsifying dietary fat, and
then reconstructed in the intestinal cells to form lipoprotein particles, which can circulate safely
Fatty acid structures
Fatty acid structures vary in chain length, and in the number and location of double bonds
The degree of unsaturation will control membrane fluidity, and specific families of unsaturated
fatty acids also fulfil metabolic roles
One aspect of nomenclature that is rarely used correctly is the difference between a name like
palmitic acid, versus palmitate
oThe name palmitic acid implies that the carboxylic acid group is protonated, which will
only be true at very low pH
Free fatty acids at physiological pH will have deprotonated carboxylate groups,
and 16:0 under these conditions should be referred to as palmitate - this aspect of
nomenclature is rarely followed
find more resources at oneclass.com
find more resources at oneclass.com
Fatty acid nomenclature
There are two main naming systems used for fatty acids, the delta system and the omega
system
oThe naming of fatty acid molecules depends on the number of carbons, and on the
number and position of the double bonds
To identify a double bond, we can describe its position in reference to the
carboxylate end or the methyl end of the fatty acid
In the delta system, numbering starts from the carboxyl end of the fatty acid
In the omega system, numbering starts from the methyl end of the fatty acid
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Describe the classification and structure of lipids. Describe the digestion and absorption of dietary lipids. Describe the function of dietary lipids in the human body. Describe the metabolism of dietary lipids, and predict how metabolism would change under different conditions. Describe the impact of essential dietary lipids on human health. Apply principles of nomenclature to novel lipid structures. Soluble in organic solvents: wide variety of structures and functions o o. Metabolically speaking, lipids are a source of energy and have roles in signalling, as precursors for hormones and eicosanoids. Other important roles include being components of cell and organelle membranes. Most of the lipids are built on fatty acids, while some have a sterol, or cholesterol base. The general formula has an r that can be a long linear carbon-hydrogen chain. There are two categories - saturated and unsaturated. Saturated: with maximum number of h per c atoms; only single bonds.
