Biology Practice Test

Correct Answer: A

Rationale: The correct answer is A: Proteins. Proteins are the most significant contributor to cellular function as they play crucial roles in almost all biological processes. They act as enzymes that catalyze reactions, are involved in cell signaling pathways, and provide structural support to cells. Phospholipids (Choice B), while important for cell membrane structure, do not have the same diverse functions as proteins in cellular processes. Carbohydrates (Choice C) primarily serve as an energy source and structural components but are not as versatile in cellular functions as proteins. Fatty acids (Choice D) are essential components of cell membranes and energy storage molecules but do not have the same broad range of functions as proteins in cellular processes.

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.

Correct Answer: C

Rationale: Mitochondria are known as the powerhouse of the cell because they generate most of the cell's supply of ATP, which is the energy currency used for various cellular processes. The nucleus (Choice A) is the control center of the cell, housing genetic material. Chromatin (Choice B) is a complex of DNA and proteins within the nucleus. Ribosomes (Choice D) are responsible for protein synthesis and not the primary energy production in the cell.

Correct Answer: D

Rationale: The correct answer is D, Steroids. Steroids are a type of lipid that function as essential components of cell membranes and serve as precursors for significant hormones like estrogen and testosterone. Nucleic acids (choice A) are not lipids but are molecules like DNA and RNA that store genetic information. Proteins (choice B) and carbohydrates (choice C) are biomolecules but are not lipids and do not serve as precursors for hormones or membrane components.

Correct Answer: C

Rationale: The correct answer is C, the citric acid cycle (the Krebs cycle). This cycle generates NADH and FADH2, which play a crucial role in providing electrons to the electron transport chain during cellular respiration. Choice A, the electron transport chain itself, is where NADH and FADH2 donate their electrons, not where they are produced. Choice B, glycolysis, produces NADH but not FADH2. Choice D, 'None of these,' is incorrect as the citric acid cycle specifically produces NADH and FADH2.