Nokea
How many different types of nucleotides are there in DNA?
- A. one
- B. two
- C. four
- D. eight
Correct Answer: C
Rationale: The correct answer is 'C: four.' DNA is composed of four different types of nucleotides: adenine, thymine, guanine, and cytosine. These nucleotides pair up in specific combinations to form the genetic code. Choices 'A: one,' 'B: two,' and 'D: eight' are incorrect because DNA consists of a set of four distinct nucleotides, not one, two, or eight.
You may also like to solve these questions
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.
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.
Which organelle is responsible for organizing protein synthesis?
- A. Nucleus
- B. Ribosome
- C. Lysosome
- D. Vacuole
Correct Answer: B
Rationale: The correct answer is B: Ribosome. Ribosomes are responsible for organizing protein synthesis by assembling amino acids. They are the cellular machinery where proteins are synthesized. The other choices, such as the nucleus, lysosome, and vacuole, do not directly participate in protein synthesis. The nucleus contains DNA and controls cell activities, the lysosome is involved in digestion and waste removal, and the vacuole is responsible for storage and maintaining cell turgor pressure.
How does water affect the temperature of a living thing?
- A. Water increases temperature.
- B. Water keeps temperature stable.
- C. Water decreases temperature.
- D. Water does not affect temperature.
Correct Answer: B
Rationale: Water has a high specific heat capacity, which means it can absorb and release large amounts of heat with minimal temperature change. This property helps water regulate the temperature of living things by maintaining a stable environment. Choice A is incorrect because water does not consistently increase temperature, but rather helps in temperature regulation. Choice C is incorrect as water doesn't typically decrease temperature in living organisms. Choice D is incorrect since water does play a crucial role in regulating temperature.
Which molecule is primarily responsible for storing energy in cells?
- A. Glucose
- B. ATP
- C. Fatty acids
- D. Starch
Correct Answer: B
Rationale: ATP is the correct answer because it is the molecule responsible for storing and providing energy in cells. Glucose is a source of energy but not primarily for storage. Fatty acids are more involved in energy production through oxidation. Starch is a polysaccharide used for energy storage in plants.