Knowt
IGCSE: Biological molecules
Overview of Biological Molecules
All living organisms are composed of various chemicals categorized into three main types: carbohydrates, fats (lipids), and proteins.
These molecules are organic because they contain carbon.
Common elements in these molecules include carbon (C), hydrogen (H), and oxygen (O). Only proteins also contain nitrogen (N) and sometimes sulfur (S).
Carbohydrates
Carbohydrates are large molecules formed from simple sugar units.
Monosaccharides: The simplest form of carbohydrates (e.g., glucose).
Disaccharides: Formed by two monosaccharides (e.g., maltose from two glucose molecules).
Polysaccharides: Long chains of monosaccharides (e.g., starch, glycogen, cellulose).
Types of Carbohydrates:
Monosaccharides: Single sugar molecules.
Disaccharides: Two sugar molecules linked together.
Polysaccharides: Many sugar molecules linked together.
Fats (Lipids)
Fats are large molecules made from smaller units: glycerol and fatty acids.
A fat molecule consists of one glycerol molecule bonded to three fatty acid chains.
Fats that are liquid at room temperature are known as oils.
Proteins
Proteins are made up of long chains of amino acids.
There are about 20 different amino acids that can combine in various sequences to form different proteins.
The sequence of amino acids determines the type and function of the protein.
Food Tests
Various tests can identify the presence of specific nutrients in food:
Starch Test: Add iodine solution to the food sample. A color change from orange-brown to blue-black indicates starch.
Reducing Sugars Test: Add Benedict's solution to the food sample and heat. A color change from blue to orange or brick red indicates reducing sugars.
Protein Test: Add Biuret solution to the food sample. A color change from blue to violet indicates the presence of protein.
Fats Test: Mix the food sample with ethanol, then add to cold distilled water. A cloudy or milky emulsion indicates fats or oils.
Vitamin C Test: Add DCPIP solution to the food sample. The blue color disappearing indicates the presence of vitamin C.
DNA Structure
DNA (deoxyribonucleic acid) contains the genetic instructions for growth and development.
It consists of two strands coiled into a double helix.
Each strand contains bases that pair specifically: adenine (A) with thymine (T) and cytosine (C) with guanine (G).
The base pairs are held together by hydrogen bonds.
(feel free to give me a rating)
recommended video:
IGCSE: Biological molecules
Overview of Biological Molecules
All living organisms are composed of various chemicals categorized into three main types: carbohydrates, fats (lipids), and proteins.
These molecules are organic because they contain carbon.
Common elements in these molecules include carbon (C), hydrogen (H), and oxygen (O). Only proteins also contain nitrogen (N) and sometimes sulfur (S).
Carbohydrates
Carbohydrates are large molecules formed from simple sugar units.
Monosaccharides: The simplest form of carbohydrates (e.g., glucose).
Disaccharides: Formed by two monosaccharides (e.g., maltose from two glucose molecules).
Polysaccharides: Long chains of monosaccharides (e.g., starch, glycogen, cellulose).
Types of Carbohydrates:
Monosaccharides: Single sugar molecules.
Disaccharides: Two sugar molecules linked together.
Polysaccharides: Many sugar molecules linked together.
Fats (Lipids)
Fats are large molecules made from smaller units: glycerol and fatty acids.
A fat molecule consists of one glycerol molecule bonded to three fatty acid chains.
Fats that are liquid at room temperature are known as oils.
Proteins
Proteins are made up of long chains of amino acids.
There are about 20 different amino acids that can combine in various sequences to form different proteins.
The sequence of amino acids determines the type and function of the protein.
Food Tests
Various tests can identify the presence of specific nutrients in food:
Starch Test: Add iodine solution to the food sample. A color change from orange-brown to blue-black indicates starch.
Reducing Sugars Test: Add Benedict's solution to the food sample and heat. A color change from blue to orange or brick red indicates reducing sugars.
Protein Test: Add Biuret solution to the food sample. A color change from blue to violet indicates the presence of protein.
Fats Test: Mix the food sample with ethanol, then add to cold distilled water. A cloudy or milky emulsion indicates fats or oils.
Vitamin C Test: Add DCPIP solution to the food sample. The blue color disappearing indicates the presence of vitamin C.
DNA Structure
DNA (deoxyribonucleic acid) contains the genetic instructions for growth and development.
It consists of two strands coiled into a double helix.
Each strand contains bases that pair specifically: adenine (A) with thymine (T) and cytosine (C) with guanine (G).
The base pairs are held together by hydrogen bonds.
(feel free to give me a rating)
recommended video:
