Free NLN NEX Practice Exam with Questions & Answers | Set: 3

Hydrochloric acid (HCl) is a strong acid. To neutralize an acid, a base must be added. Sodium hydroxide (NaOH) is a strong base that reacts with HCl to form water and a salt (sodium chloride). This neutralization reaction reduces the acidity of the solution. The other options—HNO₃, CH₃COOH, and H₂SO₄—are all acids and would increase acidity rather than neutralize it. The NEX Science exam often tests acid–base chemistry and emphasizes recognizing common acids and bases. Since NaOH is the only base listed, option C is correct.

Macromolecules are large, complex molecules essential for life. The four major classes of biological macromolecules are carbohydrates, lipids, proteins, and nucleic acids. Carbohydrates provide energy and structural support, lipids are involved in energy storage and membrane structure, proteins perform a wide range of functions including enzymes and transport, and nucleic acids store and transmit genetic information. DNA and RNA are examples of nucleic acids. The other answer choices—fatty acids, unsaturated fats, and phospholipids—are all types of lipids rather than separate macromolecule categories. The NEX Science exam often assesses whether students can distinguish between macromolecule categories and their subcomponents. Recognizing nucleic acids as one of the four major macromolecules is fundamental to understanding genetics, protein synthesis, and cell function.

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Water is a polar molecule because it has an unequal distribution of electrical charge, with a slightly negative oxygen atom and slightly positive hydrogen atoms. This polarity causes water molecules to attract one another through hydrogen bonding. Option C demonstrates this property because water molecules stick together (cohesion) and do not mix with nonpolar substances like oil. Oil molecules lack polarity and cannot form hydrogen bonds with water, so the two substances separate into layers. The other options describe physical movement, gravity, or resistance, none of which are direct results of polarity. The NEX Science exam frequently tests molecular properties such as polarity by connecting them to real-world examples like oil and water separation. Recognizing hydrogen bonding and cohesion as outcomes of water’s polarity is essential for answering these questions correctly.

Mitochondria are responsible for cellular respiration, which occurs in both plant and animal cells. Chloroplasts carry out photosynthesis and are found only in plant cells. Therefore, only plants can perform photosynthesis, while both plants and animals can perform cellular respiration. This distinction is a core concept in cell biology and is frequently tested on the NEX Science exam.

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Stage A in the diagram represents fertilization, where a sperm cell fuses with an egg to form a zygote. In humans, fertilization normally occurs in the fallopian tube, not in the uterus or vagina. After fertilization, the zygote undergoes cell division as it travels toward the uterus for implantation. The ovary produces and releases the egg but is not the site of fertilization. The NEX Science exam commonly tests understanding of reproductive anatomy and sequence of events in human development. Correctly identifying the fallopian tube as the site of fertilization is essential for understanding pregnancy, contraception, and reproductive health.

Extension is the movement that increases the angle between two bones at a joint. When the arm straightens at the elbow, the angle between the radius and the humerus increases, which is extension. Flexion decreases the angle between bones, circumduction is a circular movement, and retraction refers to pulling a structure backward. Understanding anatomical movement terms is essential for the NEX Science exam, especially in questions related to joints and motion.

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Combining disease prevention and health promotion provides the greatest overall impact on reducing cardiovascular disease. Prevention identifies and manages risk factors early, while health promotion encourages long-term lifestyle changes such as healthy eating, exercise, and stress reduction. Education alone increases awareness but may not change behavior. Screening without lifestyle intervention has limited long-term effectiveness. The NEX Science exam emphasizes population health strategies, making integrated prevention and promotion the most effective approach.

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This question tests understanding of the law of superposition, a fundamental principle in geology that is frequently tested on the NEX Science exam. The law of superposition states that in undisturbed sedimentary rock layers, the oldest layers are found at the bottom, while the youngest layers are found at the top. In the table shown, the soil surface is at the top, followed by Fossil D, Fossil C, Fossil B, and Fossil A at the bottom. Because Fossil A is located in the lowest rock layer, it must be the oldest fossil. Fossils found in higher layers were deposited more recently. The key word in the question is “undisturbed,” which means the layers have not been mixed or overturned by geological processes. The NEX exam often emphasizes recognizing this clue to correctly apply the law of superposition. Therefore, Fossil A is the correct answer because it represents the earliest life form preserved in the rock strata.

The respiratory system directly regulates the level of carbon dioxide (CO₂) in the blood. CO₂ is a waste product of cellular respiration and is removed from the body through exhalation. When breathing rate increases, more CO₂ is expelled, lowering blood CO₂ levels. When breathing slows, CO₂ levels rise. While the cardiovascular system transports CO₂, it does not regulate its concentration. The urinary system regulates pH and fluid balance but does not directly remove CO₂. The endocrine system controls hormones, not gas exchange. The NEX Science exam frequently emphasizes the role of the respiratory system in maintaining acid–base balance through CO₂ regulation.

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Bacterial cells are classified as prokaryotic cells, meaning they lack a membrane-bound nucleus. Instead of a nucleus, bacteria contain their genetic material in a region called the nucleoid. The nucleoid is not surrounded by a membrane and is unique to prokaryotic cells. In contrast, plant and animal cells are eukaryotic and store their DNA inside a true nucleus. Cell membranes, ribosomes, and DNA are found in all living cells, including bacteria, plants, and animals. Ribosomes in bacteria are smaller than those in eukaryotic cells, but they serve the same function of protein synthesis. Because the nucleoid region is exclusive to bacteria and other prokaryotes, option C is the correct answer. The NEX Science section frequently tests differences between prokaryotic and eukaryotic cells, making this an important concept to master.

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