Biomolecules include carbohydrates, lipids, proteins and nucleic acids. Carbohydrates include monosaccharides like glucose that join to form disaccharides like sucrose or polysaccharides like starch for storage. Lipids are insoluble in water, made of fatty acid esters, and serve as energy stores. Proteins are made of amino acid chains and perform important functions like catalysis and transport.

1.  identify and describe carbohydrates , lipids and proteins as food
substances
 state the chemical and physical properties of different food
substances

2. Biomolecules are molecules that occur naturally in living organisms.
Biomolecules include macromolecules like proteins, carbohydrates,
lipids and nucleic acids.
It also includes small molecules like primary and secondary
metabolites and natural products.
Biomolecules consists mainly of carbon and hydrogen with nitrogen,
oxygen, sulphur, and phosphorus.
Biomolecules are very large molecules of many atoms, that are
covalently bound together.

3. There are four major classes of biomolecules:
1. Carbohydrates
2. Lipids
3. Proteins
4. Nucleic acids

5.  Carbohydrates are organic molecules with the general formula CHO in a
1:2:1 ration.
 They constitute 1 to 2% of cell mass and provide the raw fuel for cellular
energy production
 They are classified based on molecular size and solubility. Smaller
molecules are more soluble than larger one!

7.  Monosaccharides are soluble (they dissolve) in water and taste sweet.

8.  Two monosaccharides are joined together by dehydration synthesis to form a disaccharide molecule.
These are also soluble in water and taste sweet..
 Sucrose (table sugar): Glucose + fructose = sucrose + water
 Lactose (milk sugar): Glucose + galactose = lactose + water
 Maltose (malt sugar): Glucose + glucose = maltose + water

9.  Polysaccharides include starch, cellulose, and glycogen.
 These long, chain-like polymers make ideal storage products due to their insolubility.
 Starch is the storage molecule synthesized from glucose by plants.
 Cellulose, which is also synthesized by plants for cell wall construction, is indigestible because we lack
enzymes for it. Cellulose provides fiber to promote peristalsis.
 Glycogen is the carbohydrate storage molecule found in muscle and liver cells. When blood sugar levels
drop, liver cells hydrolyze glycogen and release glucose to the blood
 Starch and glycogen are slightly soluble in water, cellulose is insoluble and polysaccharides do not taste
sweet.

12.  Lipids are organic molecules that are insoluble in water.
 Made of carbon, hydrogen and oxygen.
 Lipids are composed of long hydrocarbon chains and hold a large amount of energy and are energy
storage molecules.
 Lipids are generally esters of fatty acids and are building blocks of biological membranes. Most of the
lipids have a polar head and non-polar tail.
 Fatty acids can be unsaturated and saturated fatty acids.
 There are three main groups of lipids:
1. Triglycerides
2. Phospholipids
3. Steroids

13.  Saturated fats have a single bond between carbon atoms
 Monosaturated fats have a double bond between carbon atoms
 Polysaturated fats have more that one carbon-carbon double bond per molecule.
 Scientists believe that a diet high in saturated fats is unhealthy and they have linked
saturated fats to an increased risk of heart disease.

15.  Proteins are known as building blocks of life.
 Compounds contain carbon, hydrogen, oxygen, nitrogen and sometimes sulphur and
phosphorous.
 Perform variety of functions like catalyzing metabolic reactions, replication of DNA,
response to stimuli, and transporting molecules.

16.  Every protein molecule is made up of a long chain of amino acids.
 Usually large in size, that consists of one or more chains of amino acids.
 There are 20 amino acids and they all have the general formula
 Proteins differ from each other mainly in the sequences of amino acids.

18. 1. Which three elements are found in carbohydrates, lipids and proteins
2. Define the term; ‘monosaccharide’ ‘hydrolysis’ ‘condensation’ and ‘polysaccharide’
3. In which kind of food would you find the following substances, cellulose, sucrose, oil, fat and amino acids
4. What is the main function of proteins?