CARBOHYDRATES - THE BODY'S MAIN FUEL

What are Carbohydrates?

Carbohydrates are organic compounds made up of :

• Carbon (C)

• Hydrogen (H)

• Oxygen (O)

Common Formula: Cₓ(H₂O)ᵧ

Types of Carbohydrates

1. Monosaccharides (Simple Sugars)

2. Disaccharides (Double Sugars)

3. Polysaccharides (Complex Carbohydrates)

Monosaccharides

Simplest form of carbohydrates , cannot be broken down into smaller sugar units

• Glucose

• Fructose

• Galactose

Disaccharides

Forming by joining two monosaccharides

• Sucrose

• Maltose

• Lactose

Polysaccharides

Made by many monosaccharides joined together

• Starch

• Glycogen

• Cellulose

Functions of Carbohydrates

1. Provide Energy

   
   

   Carbohydrates are the primary source of energy for living organisms.

   
   

2. Store Energy

   
   

   Plants store excess carbohydrates as starch.

   
   

   Animals store excess carbohydrates as glycogen.

   
   

3. Structural support

   
   

   Cellulose forms the cell wall of plants and provides strength and support.

   
   

4. Dietary Fibre

   
   

   Some carbohydrates act as fibre and help, Prevent constipation, Maintain a healthy digestive system.

Test for Carbohydrates

Iodine Test for Starch

Method :

Add a few drops of iodine solution to the sample.

Observation:

A blue-black colour appears.

Conclusion:

Starch is present.

Figure 1 : Iodine Test for Starch

Easy Reminder

Iodine + Starch → Blue-Black Colour

Test for glucose

Add few drops of Benedict solution to the glucose solution

Immerse the solution in a water bath and heat

Can observe the colour changes as below

Blue ➞ Green ➞ Green yellow ➞ Orange ➞ Brick red ppt

Figure 2 : Benedict's Test for Glucose

Quick Summary

• Carbohydrates are made of Carbon, Hydrogen and Oxygen.

  
  

• They are the main source of energy.

  
  

• Monosaccharides → One sugar unit.

  
  

• Disaccharides → Two sugar units.

  
  

• Polysaccharides → Many sugar units.

  
  

• Plants store carbohydrates as starch.

  
  

• Animals store carbohydrates as glycogen.

  
  

• Cellulose strengthens plant cell walls.

  
  

• Iodine solution is used to test for starch.