Grade 7 – Nutrition and Digestion Quiz

Which organ is the primary site of nutrient absorption in the digestive system?

• Stomach

• Small Intestine

• Large Intestine

• Esophagus

Answer explanation

The small intestine is the primary site of nutrient absorption in the digestive system, where most digestion and absorption of nutrients occurs, unlike the stomach, large intestine, or esophagus.

What is the main function of the stomach during digestion?

• Absorbing water

• Grinding food and mixing it with digestive juices

• Pumping blood

• Filtering toxins

Answer explanation

The main function of the stomach during digestion is grinding food and mixing it with digestive juices. This process helps break down food into smaller particles, making it easier for nutrients to be absorbed later in the digestive tract.

Which food group is mainly responsible for providing energy through carbohydrates?

• Fruits and Vegetables

• Grains and Cereals

• Proteins

• Dairy Products

Answer explanation

Grains and cereals are the primary food group that provides energy through carbohydrates, making them essential for fueling the body. Fruits and vegetables also contain carbs, but grains are the main source.

Which test is used to detect the presence of glucose in a food sample?

• Iodine Test

• Biuret Test

• Benedict’s Test

• Ethanol Test

Answer explanation

Benedict’s Test is specifically used to detect reducing sugars, including glucose, in food samples. The other tests mentioned are for starch (Iodine), proteins (Biuret), and lipids (Ethanol), making Benedict’s the correct choice.

A positive result in Benedict’s test for glucose is indicated by a color change from blue to which of the following?

• Green, yellow, or brick red (depending on glucose concentration)

• Purple

• Orange

• No change

Answer explanation

A positive Benedict's test for glucose shows a color change from blue to green, yellow, or brick red, depending on the concentration of glucose present. Thus, the correct answer is the first option.

Which test is used to detect starch in a food sample?

• Benedict’s Test

• Iodine Test

• Biuret Test

• Sudan III Test

Answer explanation

The Iodine Test is specifically used to detect starch in food samples. When iodine is added to starch, it forms a blue-black complex, indicating the presence of starch, unlike the other tests listed.

When starch is present, the iodine test turns the sample what color?

• Red

• Blue-black

• Green

• Yellow

Answer explanation

The iodine test is used to detect starch. When starch is present, the iodine forms a complex with it, resulting in a blue-black color. Therefore, the correct answer is blue-black.

The Biuret test is used to detect the presence of which nutrient?

• Fats

• Proteins

• Carbohydrates

• Vitamins

Answer explanation

The Biuret test specifically detects proteins by reacting with peptide bonds. It is not used for fats, carbohydrates, or vitamins, making proteins the correct answer.

In the Biuret test, a positive result for proteins is shown by a change in color to:

• Blue to purple

• Green to yellow

• Red to orange

• No change

Answer explanation

In the Biuret test, proteins react with copper ions, resulting in a color change from blue to purple. This indicates the presence of peptide bonds, confirming a positive result for proteins.

Which test is commonly used to detect fats in a food sample?

• Biuret Test

• Iodine Test

• Ethanol Test

• Benedict’s Test

Answer explanation

The Ethanol Test is used to detect fats in food samples. When ethanol is added to a sample containing fats, a cloudy emulsion forms, indicating the presence of lipids. Other tests listed are for proteins or carbohydrates.