Biological Molecules and DNA Structure

This video tutorial covers Cambridge IGCSE Biology topic 4.1 on biological molecules. It explains the chemical elements and structures of carbohydrates, fats, proteins, and nucleic acids. The video also describes chemical tests for detecting these molecules and details the structure of DNA. The lesson follows the Cambridge syllabus and prepares students for their final exams.

What are the four major classes of biological molecules?

• Carbon, Hydrogen, Oxygen, Nitrogen

• Glucose, Starch, Cellulose, Glycogen

• Sugars, Fats, Enzymes, DNA

• Carbohydrates, Lipids, Proteins, Nucleic Acids

Which elements make up carbohydrates?

• Carbon, Sulfur, Phosphorus

• Hydrogen, Oxygen, Nitrogen

• Carbon, Hydrogen, Oxygen

• Carbon, Nitrogen, Oxygen

What is the primary storage form of glucose in animals?

• Cellulose

• Starch

• Sucrose

• Glycogen

What is a triglyceride composed of?

• Two fatty acids and one glycerol

• Three fatty acids and one glycerol

• Two glycerols and one fatty acid

• Three glycerols and one fatty acid

Which of the following is NOT a function of proteins?

• Storing genetic information

• Catalyzing chemical reactions

• Forming structural components of cells

• Transporting oxygen

What color change indicates the presence of starch when iodine is added?

• Blue to green

• Purple to pink

• Brown to blue-black

• Red to yellow

Which test is used to detect the presence of proteins?

• Biuret test

• Iodine test

• Emulsion test

• Benedict's test

What is the shape of a DNA molecule?

• Single helix

• Double helix

• Triple helix

• Quadruple helix

Which bases pair together in DNA?

• A with T, C with G

• A with A, C with C

• A with C, T with G

• A with G, C with T

What is the sugar component of a DNA nucleotide?

• Fructose

• Glucose

• Deoxyribose

• Ribose