LIPIDS
- Lipids are the molecules that contain hydrocarbons and make up the building blocks of the structure and function of living cells.
- Examples of lipids include fats, oils, waxes, certain vitamins, hormones and most of the non-protein membrane of cells.
- Contain carbon, hydrogen and oxygen.
- Lipids are not soluble in water. They are non-polar and are thus soluble in nonpolar environments like in choloroform but not soluble in polar environments like water.
- Lipids have mainly hydrocarbons in their composition and are highly reduced forms of carbon.
- When metabolized, lipids are oxidized to release large amounts of energy and thus are useful to living organisms.
- Lipids can contain twice the amount of energy as the same amount of carbohydrate.
- Lipids are molecules that can be extracted from plants and animals using non polar solvents such as ether, chloroform and acetone.
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3 major categories of lipids:
1. Trigylcerides
- Better known as the fats.
- Composed of one molecule of glycerol and joined via ester bonds with three molecules of fatty acids.
- Fatty acids are long chains of carbon and hydrogen usually between 14-24 carbons long (and they always have an even number of carbons). Due to the abundance of C and H, fatty acids are very hydrophobic and are not very soluble in water.
- Considered for efficient energy storing as more energy could be stored in a pound of fat compared to a pound of carbohydrates like glycogen.
- Fatty acids come in two major types:
1. Trigylcerides
- Better known as the fats.
- Composed of one molecule of glycerol and joined via ester bonds with three molecules of fatty acids.
- Fatty acids are long chains of carbon and hydrogen usually between 14-24 carbons long (and they always have an even number of carbons). Due to the abundance of C and H, fatty acids are very hydrophobic and are not very soluble in water.
- Considered for efficient energy storing as more energy could be stored in a pound of fat compared to a pound of carbohydrates like glycogen.
- Fatty acids come in two major types:
- Saturated
- "completely saturated" with H and have no double bonds.
- Carbon skeleton of fatty acid is bonded to maximum number of hydrogen (saturated with H)
- High melting point so that they are a solid at room temperature.
- Found in animals.
- Eg: Bacon grease, lard and butter.
- Not saturated with H and it contains double bonds.
- Molecules do not pack closely enough to solidify at room temperature.
- Low melting point and are a liquid at room temperature.
- Found in plants.
- Eg: Corn, peanut and olive oil.
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2. Steroids
- Hydrophobic molecules, derivatives from a common structure made up of 4 fused carbon rings.
- Tetracyclic skeleton, consisting of three fused six-membered and one five-membered ring.
- Each different steroid contains different chemical groups attached to these ring.
- Two major functions of steroids: as a significant part of the structure of cell membranes and as hormones.
- Hydrophobic molecules, derivatives from a common structure made up of 4 fused carbon rings.
- Tetracyclic skeleton, consisting of three fused six-membered and one five-membered ring.
- Each different steroid contains different chemical groups attached to these ring.
- Two major functions of steroids: as a significant part of the structure of cell membranes and as hormones.
3. Phosholipids
- Derivatives of triglycerides that consist of a glycerol molecule with two fatty acids, a phosphate group on the third carbon usually some added polar molecule (such as ethanolamine, serine or choline).
- Composed of a glycerol molecule with two fatty acids (a diglyceride).
- Consists of hydrophobic tail and hydrophilic head.
- Serve as the basis for the structure of all the membranes of the cell. Eg: Phospholipid bilayer of the cytoplasm.
- Derivatives of triglycerides that consist of a glycerol molecule with two fatty acids, a phosphate group on the third carbon usually some added polar molecule (such as ethanolamine, serine or choline).
- Composed of a glycerol molecule with two fatty acids (a diglyceride).
- Consists of hydrophobic tail and hydrophilic head.
- Serve as the basis for the structure of all the membranes of the cell. Eg: Phospholipid bilayer of the cytoplasm.
LIPID METABOLISM