CIE iGCSE Co-Ordinated Science B4. Biological molecules Exam Style Questions Paper 1
Question
Which row matches the nutrient to the chemical elements that it contains?
▶️Answer/Explanation
Answer: B
Explanation: Proteins are made up of amino acids, which contain carbon, hydrogen, oxygen, and nitrogen. Fats contain carbon, hydrogen, and oxygen, while starch and sugars are carbohydrates that contain carbon, hydrogen, and oxygen but no nitrogen.
Question
Three food tests are carried out on a sample of food. The results are shown in the table.
| Food Test | Final Colour |
|---|---|
| Benedict’s | Blue |
| Biuret | Blue |
| Iodine | Blue-black |
From these results, which nutrient is in the food?
A. reducing sugar
B. protein
C. starch
D. vitamin C
▶️Answer/Explanation
Answer: C
Explanation: The iodine test turning blue-black indicates the presence of starch. Benedict’s test for reducing sugars and Biuret test for proteins both resulted in blue, indicating no reducing sugars or proteins were present.
Question
Which row shows a large molecule and a basic unit from which it is made?
| Large molecule | Basic unit |
|---|---|
| A. glycogen | amino acid |
| B. glycogen | glucose |
| C. oil | amino acid |
| D. oil | glucose |
▶️Answer/Explanation
Answer: B. glycogen – glucose
Explanation: Glycogen is a large molecule made up of glucose units. It is a polysaccharide that serves as a form of energy storage in animals.
Question
Which chemical element is found in all proteins, but not in all carbohydrates or fats?
A carbon
B hydrogen
C oxygen
D nitrogen
▶️Answer/Explanation
Ans 😀
Question
Which reagent is used to test for the presence of protein in a food sample?
A Benedict’s solution
B biuret
C ethanol
D iodine
▶️Answer/Explanation
Ans :A
Question
Which small molecules are joined together to make a starch molecule?
A amino acids
B fatty acids
C glucose
D glycerol
▶️Answer/Explanation
Ans : C
Question
Glycerol is a component of which large molecules?
(A) fats
(B) glycogen
(C) proteins
(D) starch
▶️Answer/Explanation
Ans: A
Question
Glycerol is a component of which large molecules?
(A) fats
(B) glycogen
(C) proteins
(D) starch
▶️Answer/Explanation
Ans: A
Question
Glycerol is a component of which large molecules?
(A) fats
(B) glycogen
(C) proteins
(D) starch
▶️Answer/Explanation
Ans : A
Question
Tests are carried out on a colourless liquid. The results are shown.
Which food groups does the liquid contain?
A protein and fat
B protein and starch
C reducing sugar and fat
D starch and fat
▶️Answer/Explanation
Ans : A
Question
Which row shows the elements and the small molecules that are used to make the larger
molecules?
▶️Answer/Explanation
Ans : D
Question
Linoleic acid is a fatty acid.
Which larger molecule may contain linoleic acid?
(A) glycogen
(B) oil
(C) protein
(D) starch
▶️Answer/Explanatio
Ans : B
Question
Which food test requires heating?
(A) fat
(B) protein
(C) reducing sugar
(D) starch
▶️Answer/Explanation
Ans: C
Question
A colourless liquid gives the test results shown.
Which nutrients are in the colourless liquid?
(A) protein, reducing sugar and starch
(B) protein and reducing sugar only
(C) protein and starch only
(D) protein only
▶️Answer/Explanation
Ans: C
Question
Which colour does Benedict’s solution change to when heated with a reducing sugar?
(A) blue
(B) blue-black
(C) orange
(D) purple
▶️Answer/Explanation
Ans : C
Question
Which smaller molecules is glycogen made from?
(A) amino acids
(B) fatty acids
(C) glucose
(D) glycerol
▶Answer/Explanation
Ans : C
Question
Which smaller molecules make up larger fat molecules?
(A) glucose and amino acids
(B) glucose and fatty acids
(C) glycerol and amino acids
(D) glycerol and fatty acids
▶️Answer/Explanation
Ans: D
Question
What are the molecules that make up fats and oils?
A. amino acids and glycerol
B. fatty acids and glycerol
C. glucose and amino acids
D. glucose and fatty acids
▶️Answer/Explanation
Answer: B
Explanation: Fats and oils are composed of fatty acids and glycerol. These molecules combine to form triglycerides, which are the main constituents of fats and oils. Amino acids are the building blocks of proteins, and glucose is a simple sugar, so options A, C, and D are incorrect.
Question
Nutrient molecules are made up from smaller molecules. Nutrients can be identified by food tests. Which row is true for a protein?
| smaller molecules | test which gives a positive result | |
|---|---|---|
| A | amino acids | Benedict’s test |
| B | amino acids | biuret test |
| C | sugars | Benedict’s test |
| D | sugars | biuret test |
▶️Answer/Explanation
Answer: B. amino acids, biuret test
Explanation: Proteins are made up of amino acids, and the biuret test is used to detect the presence of proteins. Benedict’s test is used for reducing sugars, not proteins.
Question
Which type of biological molecule contains carbon, hydrogen, oxygen, and nitrogen?
A) fat
B) protein
C) reducing sugar
D) starch
▶️Answer/Explanation
Answer: B) protein
Explanation: Proteins are biological molecules that contain carbon, hydrogen, oxygen, and nitrogen. Fats and carbohydrates (like reducing sugar and starch) contain carbon, hydrogen, and oxygen but do not contain nitrogen.
Question
What colour does Benedict’s solution change to when heated with a reducing sugar?
A. blue
B. blue-black
C. orange
D. purple
▶️Answer/Explanation
Answer: C. orange
Explanation: Benedict’s solution is used to test for reducing sugars. When heated with a reducing sugar, it changes from blue to orange or brick-red, indicating the presence of the sugar.
Question
A food contains reducing sugar, but no starch. What colours will be obtained if samples of the food are tested with Benedict’s solution and with iodine solution?
| Benedict’s test | iodine test | |
|---|---|---|
| A | blue | blue-black |
| B | blue | brown |
| C | red-orange | blue-black |
| D | red-orange | brown |
▶️Answer/Explanation
Answer: D. red-orange, brown
Explanation: Benedict’s solution turns red-orange in the presence of reducing sugars, while iodine solution remains brown in the absence of starch. Therefore, the correct answer is D.
Question
Which result with the biuret test shows that protein is present?
A. blue
B. green
C. orange
D. purple
▶️Answer/Explanation
Answer: D. purple
Explanation: The biuret test is used to detect the presence of proteins. When the biuret reagent is added to a solution containing proteins, the solution turns purple, indicating the presence of proteins.
Question
Which chemical element is found in proteins, but not in carbohydrates or fats?
A. carbon
B. hydrogen
C. oxygen
D. nitrogen
▶️Answer/Explanation
Answer: D
Explanation: Nitrogen is a key element found in proteins (in the form of amino acids) but is not present in carbohydrates or fats. Carbohydrates and fats are primarily composed of carbon, hydrogen, and oxygen.