MCQ 21:
Which of the following is the primary component of cell membranes?
A) Carbohydrates
B) Proteins
C) Nucleic acids
D) Phospholipids
Answer: D) Phospholipids
Explanation: Phospholipids form the fundamental structure of cell membranes, creating a bilayer that separates the interior of the cell from the external environment. Carbohydrates and proteins play supporting roles, while nucleic acids are not structural components of membranes.
MCQ 22:
Which type of RNA carries the genetic information from DNA to the ribosome?
A) rRNA
B) tRNA
C) mRNA
D) hnRNA
Answer: C) mRNA
Explanation: Messenger RNA (mRNA) carries the genetic code from DNA to the ribosome, where proteins are synthesized. Ribosomal RNA (rRNA) is part of the ribosome structure, and transfer RNA (tRNA) brings amino acids during protein synthesis.
MCQ 23:
What is the function of enzymes in biochemical reactions?
A) To change the equilibrium of the reaction
B) To increase the activation energy
C) To speed up the reaction rate
D) To become products of the reaction
Answer: C) To speed up the reaction rate
Explanation: Enzymes catalyze biochemical reactions by lowering the activation energy, thus increasing the reaction rate. They do not change the equilibrium of the reaction and are not consumed in the process.
MCQ 24:
Which of the following is an example of a heteropolymer?
A) Glycogen
B) Cellulose
C) DNA
D) Starch
Answer: C) DNA
Explanation: DNA is a heteropolymer because it is composed of different types of nucleotides (adenine, thymine, cytosine, guanine). Glycogen and starch are homopolymers of glucose, while cellulose is a homopolymer made of glucose units.
MCQ 25:
Which of the following vitamins is primarily involved in vision?
A) Vitamin A
B) Vitamin D
C) Vitamin E
D) Vitamin K
Answer: A) Vitamin A
Explanation: Vitamin A is essential for vision, particularly for the synthesis of rhodopsin, a pigment in the retina. Vitamins D, E, and K have different roles in the body, such as calcium metabolism and antioxidant functions.
MCQ 26:
What type of bond forms between the sugar and phosphate groups in nucleic acids?
A) Hydrogen bonds
B) Peptide bonds
C) Glycosidic bonds
D) Phosphodiester bonds
Answer: D) Phosphodiester bonds
Explanation: Phosphodiester bonds link the sugar of one nucleotide to the phosphate group of another in nucleic acids, forming the backbone of DNA and RNA. Hydrogen bonds occur between base pairs, and glycosidic bonds link sugars in carbohydrates.
MCQ 27:
Which of the following amino acids is a precursor for the neurotransmitter serotonin?
A) Tyrosine
B) Tryptophan
C) Phenylalanine
D) Glutamate
Answer: B) Tryptophan
Explanation: Tryptophan is the amino acid precursor for serotonin, a neurotransmitter that regulates mood. Tyrosine and phenylalanine are precursors for dopamine and norepinephrine, while glutamate is an important neurotransmitter itself.
MCQ 28:
Which of the following is a primary structure of proteins?
A) Alpha-helix
B) Beta-sheet
C) Polypeptide chain
D) Disulfide bridge
Answer: C) Polypeptide chain
Explanation: The primary structure of proteins refers to the linear sequence of amino acids in a polypeptide chain. Alpha-helices and beta-sheets are forms of secondary structure, while disulfide bridges are involved in tertiary and quaternary structures.
MCQ 29:
Which type of lipid is important for long-term energy storage?
A) Phospholipids
B) Steroids
C) Triglycerides
D) Glycolipids
Answer: C) Triglycerides
Explanation: Triglycerides are the main form of stored energy in animals and plants. They consist of three fatty acids attached to a glycerol molecule. Phospholipids and glycolipids are important for cell membranes, and steroids have various functions in signaling.
MCQ 30:
Which of the following molecules acts as an energy carrier in the cell?
A) DNA
B) RNA
C) ATP
D) Protein
Answer: C) ATP
Explanation: ATP (adenosine triphosphate) is the primary energy carrier in cells, providing energy for various biochemical reactions. DNA and RNA are genetic materials, while proteins perform a wide range of functions.
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