Classifying Types of Lipids: Triglycerides, Phospholipids, Sterols
Lipids include a structurally and functionally diverse group of substances that tend to be insoluble in water, and
soluble in organic solvents like benzos, esthers, methanol
Triglycerides, Phospholipids
Triglycerides aka triacylglycerol (fat, oils) Phospholipids
Location Generated by body, mainly found in food: 95% of the lipids we Sufficient is generated by body, found abundantly in food
consume too e.g. peanuts, liver, soy
e.g. olive oil, butter
Structure 3 fatty acids + 1 glycerol (ester bond to glycerol) 2 fatty acids + 1 glycerol + 1 phosphate group
Glycerol backbone:
3 carbons
Fatty acids:
Long hydrocarbon chain
Alpha end: carboxyl/ acid group COOH
Omega end: methyl group CH3
Each one is joined to the 3 carbons on the glycerol backbone by
forming an ester bond
Properties ● Insoluble: hence will not affect cell water potential Amphiphilic:
● Physical and metabolic properties depend on ● Water soluble: hydrophilic phosphate group
constituent fatty acids ● Fat soluble: hydrophobic fatty acids
● Fats - solid at room temperature (saturated) e.g. butter In a cell membrane, the phosphate group will be facing
● Oils - liquid at room temperature (unsaturated) e.g. the interior and exterior of the cell, and hydrophobic core
olive oil will be shielded from water
Function 1)Provision of Energy 1)Structural - main component of cell membranes
● Broken down (lipolysis) when immediate energy is ● Maintains structural integrity of the cell
needed 2)Can be an emulsifier because it is amphiphilic
○ Ability to use fat as fuel is determined by FIT ● Keeps lipids soluble in water
■ F = fitness, fitter → more able
, ■ I = intensity, fat is preferred fuel for low ● Emulsifiers e.g. Mayonnaise is an emulsion of
intensity activities oil and vinegar with egg.
■ T = more trained → more able
○ Stored triglycerides are broken down to fatty acids
○ 9kcal/gram
○ For complete metabolism, lipid needs:
■ 1)oxygen: lipid is oxidised (aerobic
metabolism) to ATP (energy)
■ 2)carbohydrate, for complete metabolism
to CO2. Without carbohydrates, lipids are
broken down partially to ketones
● Storage when immediate energy is not needed
○ Largest energy store in the body
○ Mainly in adipose tissue (fat cells)
○ Can be stored in muscle cells with training
2)Cell growth:
● building blocks for membranes, especially for nerve
cells, the outer layer of fat helps in transmission of
nerve impulses.
● Triglyceride forms part of the lipid bilayer on the cell
surface membrane.
3)Structural: Cushion for internal organs, insulation
4)Regulation of metabolism
5)Transport, absorption, storage of fat-soluble vitamins e.g. Vit
A, D, E, K
6)Promotes satiety, energy dense
7)Texture and flavour in food
Sterols
Classes/ Types:
● Cholesterol: from animal products consumed, synthesised by our liver and intestine.
● Phytosterols: from plants. Role is to reduce cholesterol absorption.
Structure/ Properties:
● Multiple ring structure
● Appears as a clear, waxy substance in blood
● Lipophilic: dissolves in lipids
● Insoluble in water
Function of cholesterol:
Lipids include a structurally and functionally diverse group of substances that tend to be insoluble in water, and
soluble in organic solvents like benzos, esthers, methanol
Triglycerides, Phospholipids
Triglycerides aka triacylglycerol (fat, oils) Phospholipids
Location Generated by body, mainly found in food: 95% of the lipids we Sufficient is generated by body, found abundantly in food
consume too e.g. peanuts, liver, soy
e.g. olive oil, butter
Structure 3 fatty acids + 1 glycerol (ester bond to glycerol) 2 fatty acids + 1 glycerol + 1 phosphate group
Glycerol backbone:
3 carbons
Fatty acids:
Long hydrocarbon chain
Alpha end: carboxyl/ acid group COOH
Omega end: methyl group CH3
Each one is joined to the 3 carbons on the glycerol backbone by
forming an ester bond
Properties ● Insoluble: hence will not affect cell water potential Amphiphilic:
● Physical and metabolic properties depend on ● Water soluble: hydrophilic phosphate group
constituent fatty acids ● Fat soluble: hydrophobic fatty acids
● Fats - solid at room temperature (saturated) e.g. butter In a cell membrane, the phosphate group will be facing
● Oils - liquid at room temperature (unsaturated) e.g. the interior and exterior of the cell, and hydrophobic core
olive oil will be shielded from water
Function 1)Provision of Energy 1)Structural - main component of cell membranes
● Broken down (lipolysis) when immediate energy is ● Maintains structural integrity of the cell
needed 2)Can be an emulsifier because it is amphiphilic
○ Ability to use fat as fuel is determined by FIT ● Keeps lipids soluble in water
■ F = fitness, fitter → more able
, ■ I = intensity, fat is preferred fuel for low ● Emulsifiers e.g. Mayonnaise is an emulsion of
intensity activities oil and vinegar with egg.
■ T = more trained → more able
○ Stored triglycerides are broken down to fatty acids
○ 9kcal/gram
○ For complete metabolism, lipid needs:
■ 1)oxygen: lipid is oxidised (aerobic
metabolism) to ATP (energy)
■ 2)carbohydrate, for complete metabolism
to CO2. Without carbohydrates, lipids are
broken down partially to ketones
● Storage when immediate energy is not needed
○ Largest energy store in the body
○ Mainly in adipose tissue (fat cells)
○ Can be stored in muscle cells with training
2)Cell growth:
● building blocks for membranes, especially for nerve
cells, the outer layer of fat helps in transmission of
nerve impulses.
● Triglyceride forms part of the lipid bilayer on the cell
surface membrane.
3)Structural: Cushion for internal organs, insulation
4)Regulation of metabolism
5)Transport, absorption, storage of fat-soluble vitamins e.g. Vit
A, D, E, K
6)Promotes satiety, energy dense
7)Texture and flavour in food
Sterols
Classes/ Types:
● Cholesterol: from animal products consumed, synthesised by our liver and intestine.
● Phytosterols: from plants. Role is to reduce cholesterol absorption.
Structure/ Properties:
● Multiple ring structure
● Appears as a clear, waxy substance in blood
● Lipophilic: dissolves in lipids
● Insoluble in water
Function of cholesterol:
