- They are a broad group of molecules that includes fats, fatty acids, sterol, waxes, glycerides and phospholipids fats are a subgroup of lipids called triglycerides.
- Cholesterol is an example of the type of lipids called sterol.
- The main function of the lipids include energy storage, cell signalling and cell structure.
- Constitutes 3 elements : carbon, hydrogen and oxygen.
- 1gm gives 117kj of energy (or 4.1 kcal of energy).
- They belong to three types : monosaccharides, disaccharides and polysaccharides.
- Monosaccharides : these are the simplest form of carbohydrates, and cannot be broken down any further. Example : glucose and fructose.
- Monosaccharides dissolve in water, taste sweet and are called sugars.
- Used as an energy source and in biosynthesis.
- Disaccharides : disaccharides are compounds made by two monosaccharides bond together. Example : sucrose and lactose used for carbohydrate transport.
- Like monosaccharides, disaccharides dissolve in water.
- Polysaccharides : these are compounds made by complex chains of monosaccharides. Example : cellulose and glucose.
- Used for energy storage (glycogen) and for cell walls (cellulose).
- Cellulose is the most abundant organic molecule on earth.
- Spider silk is a polysaccharide.
- During the process of digestion, all carbohydrates are broken down to monosaccharides.
- They are molecules that contain an amine group and a carboxyl group.
- Example: glycine, monosodium glutamate.
- They are the building blocks of the proteins.
- Applications include metabolism, drug therapy, flavour enhancement, manufacture of biodegradable plastics.
- They are compounds made from amino acids.
- Proteins are used as enzymes, in muscle formation, as cell cytoskeleton, cell signalling and immune response.
- Made up of carbon, hydrogen, oxygen, nitrogen and sometimes sulphur.
- Important for growth repair of the body. (75% of our body is proteins only).
- Proteins are first broken into amino acids and then digested.
- Protein energy malnutrition :
- Kwashiorkor : due to deficiency of protein.
- Means neglected child ( when mother stops breastfeeding )
- Marasmus : deficiency of proteins, carbohydrates and fats.
- They are macromolecules formed by chains of nucleotides.
- Common examples include DNA and RNA.
- DNA (deoxyribonucleic acid)
- Contains two strands of nucleotides arranged in a double helix structure.
- In cells, DNA is organised into long structures called chromosomes.
- Used primarily for long term storage of genetic information.
- DNA was first isolated by swiss physician Friedrich Miescher in 1869.
- The double helix structure was suggested by James Watson and Francis Crick.
- RNA (ribonucleic acid)
- Contains one strand of nucleic acids.
- Less stable than DNA.
- Used primarily for protein synthesis.
- Messenger RNA carries information from DNA to the ribosomes. RNA translates the information in the mRNA.
- RNA synthesis was discovered by Severo Ochoa.
- Provides twice the energy of carbohydrates.
- Acts as the reserve food Material because excess fat is stored in the liver and as adipose tissue.
- An enzyme called lipase digests fats.
- There are two types of fatty acids : saturated fatty acids : solids at room temperature, unsaturated fatty acids : liquids at room temperature.
- Fatty acids are basic chemical units of fat.
- Saturated fat is used by the liver to manufacture cholesterol.
- Is considered the most dangerous kind of fat because it has shown to raise blood cholesterol levels, particularly the LDL.
- Polyunsaturated fats : do not appear to raise blood cholesterol levels.
- Monounsaturated fats : Do not seem to have any effect on blood cholesterol.
- Trans fat : byproducts of hydrogenation, a chemical process used to change liquid unsaturated fat to a more solid fat.
- Total fat intake should be no more than 30 percent of your daily calorie intake.
- Hydrogenation : process by which unsaturated fatty acids are converted into saturated fatty acids by the addition of hydrogen.