Nokea
Which of the following organelles is the site of cellular respiration?
- A. Nucleus
- B. Mitochondria
- C. Lysosomes
- D. Ribosomes
Correct Answer: B
Rationale: The correct answer is B: Mitochondria. Mitochondria are known as the powerhouse of the cell because they generate most of the cell's supply of ATP through cellular respiration. The other organelles listed, such as the nucleus (choice A), lysosomes (choice C), and ribosomes (choice D), do not play a direct role in cellular respiration. The nucleus contains genetic material, lysosomes are involved in digestion and waste removal, and ribosomes are responsible for protein synthesis.
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What characteristic of water allows for hydrogen bonding between molecules?
- A. Its covalent bonds
- B. Its cohesive properties
- C. Its high specific heat
- D. Its polar nature
Correct Answer: D
Rationale: The correct answer is D: Its polar nature. Water is a polar molecule with a partial positive charge on hydrogen atoms and a partial negative charge on oxygen atoms. This polarity allows water molecules to form hydrogen bonds with each other. Choice A, covalent bonds, is incorrect because while water indeed has covalent bonds, they do not directly enable hydrogen bonding. Choice B, cohesive properties, is incorrect as cohesion refers to water's ability to stick to other substances, not the specific characteristic that allows for hydrogen bonding. Choice C, high specific heat, is also incorrect as it refers to water's ability to resist changes in temperature, not its property that leads to hydrogen bonding.
Which of the following is not one of the four nitrogenous bases that make up the DNA structure?
- A. Adenine
- B. Guanine
- C. Uracil
- D. Thymine
Correct Answer: C
Rationale: The correct answer is C: Uracil. Uracil is found in RNA, not DNA. The four nitrogenous bases in DNA are adenine, thymine, cytosine, and guanine. Choice A, Adenine, is a nitrogenous base in DNA. Choice B, Guanine, is another nitrogenous base in DNA. Choice D, Thymine, is also one of the four nitrogenous bases in DNA. Therefore, the correct answer is Uracil (Choice C).
Water is held together by which of the following bonds?
- A. Electrostatic attraction
- B. Van der Waals forces
- C. Hydrogen
- D. Oxygen
Correct Answer: C
Rationale: Water molecules are held together by hydrogen bonds, which are weak bonds formed between the slightly positive hydrogen atom of one water molecule and the slightly negative oxygen atom of another. Choice A, electrostatic attraction, is a general term for the attraction between opposite charges but does not specifically describe the bonds in water. Choice B, Van der Waals forces, are weak intermolecular forces that arise from temporary fluctuations in electron distribution, not the primary bonds in water. Choice D, oxygen, is incorrect as oxygen is part of the water molecule but not the bond holding water molecules together.
What is located on the rough endoplasmic reticulum?
- A. Microvilli
- B. Mitochondria
- C. Lysosomes
- D. Ribosomes
Correct Answer: D
Rationale: The rough endoplasmic reticulum is studded with ribosomes, which are responsible for protein synthesis. Ribosomes are the correct answer because they are the organelles directly associated with the rough endoplasmic reticulum. Microvilli (choice A), mitochondria (choice B), and lysosomes (choice C) are not typically located on the rough endoplasmic reticulum. Microvilli are found on the surface of cells to increase surface area, mitochondria are the powerhouses of the cell responsible for energy production, and lysosomes are membrane-bound organelles containing digestive enzymes.
The liver is an organ responsible for detoxifying the body of many harmful substances. You might expect the liver to contain a high amount of which of the following?
- A. Rough endoplasmic reticulum
- B. Smooth endoplasmic reticulum
- C. Mitochondria
- D. Lysosomes
Correct Answer: B
Rationale: The correct answer is B: Smooth endoplasmic reticulum. The liver contains a high amount of smooth endoplasmic reticulum because it plays a significant role in detoxification processes, such as the synthesis of detoxifying enzymes and lipids. Choice A (Rough endoplasmic reticulum) is incorrect because the rough endoplasmic reticulum is more involved in protein synthesis and processing. Choice C (Mitochondria) is incorrect as mitochondria are primarily responsible for energy production. Choice D (Lysosomes) is incorrect because lysosomes are organelles involved in intracellular digestion and waste removal, not specifically related to detoxification.