Quick overview for O-level Biology (Biological molecules)

Here are some essential points for the topic of Biological molecules:

1. Water is essential for all organisms such as plants & animals. Thus we need to know some of its uses. Examples include usage for thermoregulation & the transport of substances
   

2. Carbohydrates

• An organic molecule made up of carbon, hydrogen & oxygen

• Generic formula: C(n)H(2n)O(n)

• An individual carb molecule contains 4kcals of energy

• 3 types: Monosaccharides, Disaccharides & polysaccharides (What are some examples?)

• The uses of carbohydrates are usually as a source of energy or structural support (what are some examples?)

• Condensation reaction of monosaccharides to form di/polysaccharides

• Hydrolysis reaction to derive monosaccharides from di/polysaccharides

• Food tests: Benedict's test/ Iodine test to identify the presence of reducing sugar or starch
  

3.1 Proteins

• An organic molecule made up of carbon, hydrogen, oxygen, NITROGEN & sometimes sulfur

• The smallest unit is known as an amino acid

• An amino acid provides 4kcal of energy

• Amino acid general structure: Amino grp, Carboxyl grp, Variable R grp & Hydrogen

• Amino acids are linked together by peptide bonds (condensation reaction)

• A chain of amino acids is known as a polypeptide

• Multiple/single polypeptides fold into proteins

• Proteins are used to form tissue in organisms & enzymes

• Food tests: Biuret's test to identify the presence of protein

3.2 Enzymes

• Act as catalysts that speed up biological reactions (lower activation energy) & are not modified in the process & can be reused

• Enzymes are substrate specific due to the specific shape of their active site

• Lock & key hypothesis: Key is the substrate while lock is the enzyme. The substrate must fit in the active site of the enzyme for the reaction to occur

• Steps of catalysis: Substrate enters enzyme active site, enzyme-substrate complex formation (catalysis), the release of products from enzyme

• Factors that affect enzyme-catalyzed reactions: Temperature & pH

• Denaturation: Destruction of the active site in the enzyme rendering it permanently useless & unable to carry out further reactions

4. Fats

• An organic molecule made up of carbon, hydrogen & oxygen

• Composed of 1 glycerol molecule to 3 fatty acid molecules

• Hydrolysis of it requires 3 H20

• Each fat molecule provides 9kcal of energy

• Uses: Production of hormones, storage of energy, insulation, etc

• Food tests: Ethanol emulsion test to detect the presence of fats
  

Overall, it is important to have a strong understanding of the biological roles & chemistry behind the 3 main biomolecules to excel in O level Biology.

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