Lab 2: Biological Molecules

Biological Molecules

• Living organisms are composed of molecules with diverse shapes and forms.
• The four main classes of biological molecules are carbohydrates, proteins, lipids, and nucleic acids.

Carbohydrates

• Complex carbohydrates are made up of monosaccharides.
• Some sugars, known as reducing sugars, contain free aldehyde or ketone groups.
• Reducing sugars can be detected using Benedict's Test.

Benedict's Test

• Benedict's solution is blue and contains cupric ions.
• When heated, cupric ions react with certain sugars, forming an insoluble reddish precipitate of copper (I) oxide.
• The solution changes color from blue to green to reddish brown depending on the amount of sugar present.

Starch

• Starch is a polysaccharide produced by plants to store sugars for later energy needs.
• Starch is a primary source of carbohydrate in our diets.
• Starch interacts with iodine to produce a bluish-black color.

Proteins

• Proteins are made up of chains of amino acids.
• Biuret reagent is used to test for the presence of protein.
• Biuret reagent contains copper sulfate, which reacts with peptide bonds, resulting in a violet/lavender color.
• Only proteins with four to six linked amino acids will react with Biuret reagent.

Lipids

• Lipids vary in composition, but main components include fatty acids and glycerol.
• Sudan IV test is used to detect the presence of lipids.
• Sudan IV is not soluble in water but is soluble in lipids.
• If lipids are present, the Sudan reagent will stain the oil droplets a slightly darker red-orange color.

Biological Molecules

• Living organisms are composed of molecules with diverse shapes and forms.
• The four main classes of biological molecules are carbohydrates, proteins, lipids, and nucleic acids.

Carbohydrates

• Complex carbohydrates are made up of monosaccharides.
• Some sugars, known as reducing sugars, contain free aldehyde or ketone groups.
• Reducing sugars can be detected using Benedict's Test.

Benedict's Test

• Benedict's solution is blue and contains cupric ions.
• When heated, cupric ions react with certain sugars, forming an insoluble reddish precipitate of copper (I) oxide.
• The solution changes color from blue to green to reddish brown depending on the amount of sugar present.

Starch

• Starch is a polysaccharide produced by plants to store sugars for later energy needs.
• Starch is a primary source of carbohydrate in our diets.
• Starch interacts with iodine to produce a bluish-black color.

Proteins

• Proteins are made up of chains of amino acids.
• Biuret reagent is used to test for the presence of protein.
• Biuret reagent contains copper sulfate, which reacts with peptide bonds, resulting in a violet/lavender color.
• Only proteins with four to six linked amino acids will react with Biuret reagent.

Lipids

• Lipids vary in composition, but main components include fatty acids and glycerol.
• Sudan IV test is used to detect the presence of lipids.
• Sudan IV is not soluble in water but is soluble in lipids.
• If lipids are present, the Sudan reagent will stain the oil droplets a slightly darker red-orange color.

This quiz covers the four major classes of biological molecules, including carbohydrates, proteins, lipids, and nucleic acids, and their building blocks.