Unit 4 - Biological molecules

What color change indicates a positive test for starch when iodine solution is added?

Which of the following correctly describes a positive test for protein using Biuret solution?

In a test for lipids, what is observed to confirm a positive result?

Which bases pair correctly in DNA structure?

What structure forms the 'backbone' of a DNA molecule?

What are the primary chemical elements found in carbohydrates?

What is a disaccharide formed from two glucose molecules?

Which type of lipid is typically solid at room temperature?

What are proteins primarily composed of?

What is the role of Benedict's solution in food testing?

What color change indicates a positive test for glucose using Benedict's solution?

How many different amino acids are commonly found in proteins?

Which molecule serves as the basic unit of triglycerides?

Biological Molecules

Biological molecules—carbohydrates, proteins, and lipids—are the building blocks of life.
They all contain carbon, making them organic molecules.

Chemical Elements

Carbohydrates: Contain carbon, oxygen, and hydrogen.
Proteins: Contain carbon, oxygen, hydrogen, nitrogen, and sometimes sulfur.
Lipids: Contain carbon, oxygen, and hydrogen.

Carbohydrates: Large Molecules from Smaller

Carbohydrates are long chains of simple sugars.
Glucose is a simple sugar (monosaccharide).
Two glucose molecules form maltose (disaccharide).
Many glucose molecules form starch, glycogen, or cellulose (polysaccharides).

Fats (Lipids)

Most fats in the body are triglycerides.
Triglycerides are composed of one glycerol molecule and three fatty acid chains.
Fatty acids vary in size and structure.
Lipids are categorized as solids (fats) or liquids (oils) at room temperature.

Proteins

Proteins are long chains of amino acids.
There are about 20 different amino acids.
Amino acids have a similar basic structure but differ in their "R" group.
Amino acids link to form proteins.
The order of amino acids determines the protein's function.
A small change in amino acid order results in a different protein.

Food Tests

Glucose (reducing sugars): Benedict's solution, heated to 60-70°C, changes color from blue to orange/brick red if glucose is present.
Starch: Iodine solution changes color from orange-brown to blue-black in the presence of starch.
Proteins: Biuret solution changes color from blue to violet/purple in the presence of protein.
Lipids: A food sample mixed with ethanol, then water, forms a cloudy emulsion if lipids are present.
Vitamin C: DCPIP solution loses its blue color in the presence of Vitamin C.

Explore the foundational building blocks of life through this quiz on biological molecules, covering carbohydrates, proteins, and lipids. Learn how these organic molecules are structured and their essential roles in living organisms. Test your understanding of their components and classifications.