Nokea
Why is DNA important for the metabolic activities of the cell?
- A. It initiates cellular mitosis.
- B. It provides cell wall stability.
- C. It increases glucose absorption.
- D. It controls the synthesis of enzymes.
Correct Answer: D
Rationale: DNA is important for the metabolic activities of the cell because it controls the synthesis of enzymes. Enzymes are essential for catalyzing metabolic reactions in the cell. Choices A, B, and C are incorrect because DNA is not directly involved in cellular mitosis, cell wall stability, or glucose absorption.
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Which of the following is not found within a bacterial cell?
- A. mitochondria
- B. DNA
- C. vesicles
- D. ribosome
Correct Answer: A
Rationale: The correct answer is A: mitochondria. Mitochondria are not found in bacterial cells. Bacterial cells lack membrane-bound organelles like mitochondria, which are commonly found in eukaryotic cells. Choices B, C, and D are all components that can be found within a bacterial cell. Bacterial cells contain DNA as their genetic material, vesicles for various cellular functions, and ribosomes for protein synthesis. Therefore, the presence of mitochondria is the distinguishing factor that is not found in bacterial cells, making option A the correct answer.
What is the function of water in photosynthesis?
- A. Combine with carbon dioxide
- B. Absorb light energy
- C. Supply electrons in the light reactions
- D. Transport hydrogen ions in the dark reactions
Correct Answer: C
Rationale: The correct answer is C: 'Supply electrons in the light reactions.' In photosynthesis, water is split during the light reactions of photosynthesis, releasing electrons that are used in the formation of ATP and NADPH, crucial for the synthesis of glucose. Choice A is incorrect because water does not combine with carbon dioxide in photosynthesis. Choice B is incorrect as water does not absorb light energy directly. Choice D is incorrect because the transportation of hydrogen ions mainly occurs in the electron transport chain, which is part of the light reactions, not the dark reactions.
Which of the following is a protein?
- A. cellulose
- B. hemoglobin
- C. estrogen
- D. ATP
Correct Answer: B
Rationale: The correct answer is 'hemoglobin' because it is a protein that carries oxygen in the blood. Cellulose is a carbohydrate found in the cell walls of plants, not a protein. Estrogen is a hormone, not a protein. ATP (adenosine triphosphate) is a molecule that carries energy within cells, not a protein.
Which organelle organizes protein synthesis?
- A. mitochondrion
- B. nucleus
- C. ribosome
- D. vacuole
Correct Answer: C
Rationale: Ribosomes are the organelles responsible for organizing protein synthesis. They are the protein factories of the cell, where amino acids are linked together to form proteins. Mitochondria are known as the powerhouse of the cell, responsible for energy production. The nucleus contains the cell's genetic material but does not directly organize protein synthesis. Vacuoles are responsible for storage and maintaining the cell's turgidity.
What kind of bond connects sugar and phosphate in DNA?
- A. hydrogen
- B. ionic
- C. covalent
- D. overt
Correct Answer: C
Rationale: Sugar and phosphate are indeed connected by covalent bonds in DNA. Covalent bonds involve the sharing of electrons between atoms, which is essential for forming the backbone of the DNA molecule. Hydrogen bonds (Choice A) are important in holding the nitrogenous bases together in the DNA double helix but do not connect sugar and phosphate. Ionic bonds (Choice B) involve the transfer of electrons between atoms and are not the primary bond connecting sugar and phosphate in DNA. 'Overt' (Choice D) is not a type of chemical bond and is an incorrect distractor.