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Biology for IGCSE & O level - Biological Molecules (Section 3)

1
What is the process by which water molecules are removed to join monomers?
Answer
(B)
Dehydration synthesis
2
What is the function of base pairing in the DNA molecule?
Answer
(C)
To determine the sequence of amino acids.
3
Which of the following is a correct base pairing?
Answer
(C)
A-T, C-G
4
Which of the following is NOT a primary element in carbohydrates?
Answer
(D)
Nitrogen
5
Which of the following is NOT a correct statement about enzymes?
Answer
(C)
Enzymes are used up in the reactions they catalyze.
6
Which reagent is used to test for the presence of protein?
Answer
(C)
Biuret reagent
7
What type of bond is found between fatty acids and glycerol in a fat molecule?
Answer
(C)
Ester bond
8
What is the function of enzymes in a cell?
Answer
(B)
To speed up chemical reactions
9
What type of reaction is responsible for joining simple sugars to make complex carbohydrates?
Answer
(B)
Dehydration synthesis
10
What type of bond is found in a double helix of DNA?
Answer
(C)
Hydrogen bonds
11
What type of reaction is used to break down polymers into monomers?
Answer
(B)
Hydrolysis
12
What is a fatty acid composed of?
Answer
(C)
A long hydrocarbon chain and a carboxyl group
13
Which test is used to test for the presence of starch?
Answer
(C)
Iodine
14
What is the sugar found in the backbone of RNA?
Answer
(C)
Ribose
15
What are the elements present in all fats and oils?
Answer
(A)
Carbon, hydrogen and oxygen
16
Which of the following is a key component of a phospholipid?
Answer
(B)
Two fatty acids, a glycerol, and a phosphate group
17
What is the main function of glycogen in animals?
Answer
(B)
Long-term energy storage
18
In a DNA molecule, what type of bond connects the phosphate and the sugar?
Answer
(A)
Covalent bond
19
What is the name of the sugar found in DNA?
Answer
(C)
Deoxyribose
20
What is the role of glycerol in the formation of a fat molecule?
Answer
(A)
It forms the backbone of the molecule and binds with fatty acids.
21
Which of the following molecules is not a polymer?
Answer
(C)
Glucose
22
What type of bond joins the monomers to make a protein?
Answer
(B)
Peptide bond
23
Which of the following is a major component of plant cell walls?
Answer
(C)
Cellulose
24
What is the main function of DNA in a cell?
Answer
(C)
Storing genetic information
25
What molecules are formed from amino acids?
Answer
(B)
Proteins
26
What is the primary role of nitrogenous bases in DNA?
Answer
(C)
To store genetic information
27
Which color change indicates a positive test for protein with Biuret reagent?
Answer
(A)
Blue to violet/purple
28
What is formed when an amino acid is linked to another amino acid?
Answer
(B)
A peptide bond
29
Which of the following is a structural polysaccharide found in plants?
Answer
(C)
Cellulose
30
Which of the following best describes the primary structure of a protein?
Answer
(B)
The sequence of amino acids
31
Which of the following results is expected during a test for proteins using Biuret reagent?
Answer
(C)
Purple color
32
What are the building blocks of proteins?
Answer
(C)
Amino acids
33
Which type of molecule is formed from glycerol and fatty acids?
Answer
(C)
Lipids
34
What is the primary role of the phosphate group in a nucleotide?
Answer
(B)
To form the backbone of the DNA/RNA molecule.
35
What is the function of the enzyme amylase?
Answer
(A)
Break down of starch
36
Which of the following is not a function of lipids?
Answer
(D)
Catalyzing chemical reactions
37
What is the primary function of enzymes in biological systems?
Answer
(C)
To catalyze biochemical reactions
38
What is the result of a positive test for vitamin C (ascorbic acid) using DCPIP?
Answer
(B)
The DCPIP solution turns colorless.
39
What is the name of the process that breaks down large biological molecules into smaller ones?
Answer
(B)
Hydrolysis
40
Which of the following best describes the secondary structure of a protein?
Answer
(C)
The alpha-helices and beta-pleated sheets
41
Which of the following is a characteristic of a saturated fat?
Answer
(C)
Contains all single bonds in their carbon chains
42
Which reagent should be used to test for starch?
Answer
(C)
Iodine solution
43
What type of bond is formed between amino acids in a polypeptide chain?
Answer
(B)
Peptide bond
44
Which of the following is formed by joining several glucose molecules?
Answer
(C)
Starch
45
If an unknown substance turns Benedict's solution orange when heated, what molecule is likely present?
Answer
(C)
Reducing sugar
46
Which of the following biological molecules are polymers?
Answer
B
C
47
Which of the following pairs represents a correct base pairing in DNA?
Answer
(C)
A-T
48
What would be the color change observed during a positive test for a reducing sugar using Benedict's reagent?
Answer
(A)
Blue to green to yellow to orange/red
49
What is the bond that holds together the two strands of DNA?
Answer
(B)
Hydrogen bond
50
Which of the following is NOT a characteristic of enzymes?
Answer
(C)
They are used up in the reactions they catalyze