Free HESI A2 Biology practice for HESI A2 Biology Version 3 (HESI A2). Answer 25 nursing exam-style questions with rationales, exam mode, and progress tracking
What type of bond bonds one molecule of water with another molecule of water?
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Explanation:
Two molecules of water are bonded through hydrogen bonding. This type of bond forms between the slightly positive hydrogen atom in one water molecule and the slightly negative oxygen atom in another water molecule. Hydrogen bonds are weaker than covalent bonds but are essential in various biological processes and properties of water, contributing to its unique characteristics like high surface tension, cohesion, and adhesion.
Which of the following is a benefit of the intermolecular hydrogen bonding of water? (Select one that doesn't apply.)
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Explanation:
Intermolecular hydrogen bonding in water leads to various unique properties. Options A, B, and C are benefits of this bonding. Water's high specific heat value allows it to resist temperature changes, which is advantageous for temperature regulation in organisms. The strong cohesive and adhesive properties of water contribute to capillary action and surface tension, essential in biological systems. Additionally, water's polarity enables it to dissolve a wide range of substances, making it a versatile solvent. Option D, 'Water moves from higher to lower concentrations,' is not a direct benefit of intermolecular hydrogen bonding of water. Instead, it describes the process of osmosis, which is driven by differences in solute concentrations rather than hydrogen bonding.
Which of the following molecules are considered the most important in biology?
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Explanation:
Carbohydrates, lipids, proteins, and nucleic acids are the four main types of molecules that are fundamental to biological systems. Carbohydrates provide energy, lipids are essential for cell structure and signaling, proteins carry out diverse functions in cells, and nucleic acids store and transfer genetic information. These molecules are considered the most important in biology due to their critical roles in various biological processes.
The cell membrane consists of a bilayer of phospholipids with proteins, cholesterol, and glycoproteins. This bilayer creates a hydrophobic region between two layers of lipids, making it which of the following?
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Explanation:
The cell membrane is composed of a phospholipid bilayer with proteins, cholesterol, and glycoproteins. This structure results in the creation of a hydrophobic region between the lipid layers. The cell membrane is termed 'selectively permeable' because it allows certain substances to pass through while restricting the passage of others, based on factors like size and charge. This property is essential for regulating the transport of ions and molecules in and out of the cell to maintain cellular function and homeostasis.
What is the first step in the conversion of glucose to pyruvate?
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Explanation:
The correct answer is A: Glycolysis. Glycolysis is the initial step in the conversion of glucose to pyruvate and occurs in the cytoplasm of the cell. During glycolysis, glucose is enzymatically broken down into pyruvate, generating ATP and NADH as energy carriers. Following glycolysis, the Krebs cycle, electron transport chain, and aerobic respiration continue the breakdown of pyruvate to produce more ATP through oxidative phosphorylation and complete the cellular respiration process.
Lipids are better known as fats, but what are they specifically? (Select one that doesn't apply.)
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Explanation:
Lipids are a diverse group of molecules that include fatty acids, phospholipids, and steroids. Ketones, while important in metabolism, are not typically classified under lipids. Ketones are produced during the breakdown of fatty acids or amino acids, but they are not themselves lipids. Therefore, option C, Ketones, is the correct answer as it does not specifically fall under the category of lipids.
Why is DNA crucial for the metabolic activities of the cell?
Select the best answer.
Explanation:
DNA is crucial for the metabolic activities of the cell because it contains the genetic information necessary to regulate the synthesis of enzymes. Enzymes are essential for catalyzing biochemical reactions involved in metabolic processes within the cell. DNA controls the production of enzymes, which are vital for driving various metabolic pathways. Therefore, the correct answer is D, as DNA's role in controlling enzyme synthesis is fundamental for the cell's metabolic activities.
During protein synthesis, what process uses an RNA strand to produce a complementary strand of DNA?
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Explanation:
The correct answer is transcription. Transcription is the process in which an RNA molecule is synthesized from a DNA template. During transcription, an RNA polymerase enzyme reads the DNA template and produces a complementary RNA strand, not DNA. This RNA strand is used as a template in translation to synthesize proteins, where the mRNA is read to produce a protein.
What is the function of water in photosynthesis?
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Explanation:
In photosynthesis, water plays a crucial role in supplying electrons during the light reactions of the process. When light energy is absorbed by chlorophyll, water molecules are split through photolysis, releasing electrons. These electrons are then used in the photosynthetic electron transport chain to generate ATP and NADPH, essential for the synthesis of sugars during the light-dependent reactions.
Cells reproduce by different processes, all of which fall into what two categories?
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Explanation:
Cells can reproduce through sexual reproduction, involving the fusion of gametes, and asexual reproduction, which does not involve the fusion of gametes. Binary fission is a specific type of asexual reproduction where a cell divides into two identical cells. Therefore, the correct answer is B as it encompasses the broad categories of cellular reproduction processes, covering both sexual and asexual reproduction.
Which of the following describes how a bacterium reproduces?
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Explanation:
Binary fission is the correct answer. Bacteria reproduce asexually through binary fission, where a single cell divides into two identical daughter cells. Mitosis and meiosis are processes that occur in eukaryotic cells, not bacteria. Cytokinesis is the physical division of the cytoplasm that follows nuclear division, which is a part of the cell cycle in both eukaryotic and prokaryotic cells but not specific to bacterial reproduction.
Which cellular component contributes to the protection, communication, and passage of substances into and out of the cell?
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Explanation:
The cell membrane is responsible for protecting the cell, facilitating communication with the external environment, and controlling the passage of substances into and out of the cell. It acts as a barrier, regulating the entry and exit of molecules to maintain the cell's internal environment. The nucleus, endoplasmic reticulum, and cytoplasm have their own distinct functions within the cell but do not primarily serve the purposes mentioned in the question.
What type of bond holds molecules of water together with other water molecules?
Select the best answer.
Explanation:
The correct answer is 'C: Hydrogen.' Molecules of water are held together by hydrogen bonds. These bonds form between the hydrogen atom of one water molecule and the oxygen atom of another water molecule. Hydrogen bonds are weaker than covalent bonds but are crucial in various biological processes, such as maintaining the unique properties of water and facilitating specific interactions in biological molecules.
Which of the following is a benefit of the intermolecular hydrogen bonding of water? (Select one that doesn't apply.)
Select the best answer.
Explanation:
The process described in option D, 'Water moves from higher to lower concentrations,' is not a direct benefit of intermolecular hydrogen bonding of water. Rather, this movement of water from higher to lower concentrations is attributed to osmosis, a phenomenon driven by differences in solute concentrations across a semi-permeable membrane. The other options, A, B, and C, directly result from water's intermolecular hydrogen bonding. Water's high specific heat capacity (A) is due to the hydrogen bonds, which allow water to absorb and release large amounts of heat with minimal temperature change. The strong cohesive and adhesive properties of water (B) are a result of hydrogen bonding, enabling water to stick to other substances. Lastly, the polarity of water (C) due to hydrogen bonding makes it an effective solvent by interacting with various solutes.
In binomial nomenclature, what is the second part of an organism's scientific name?
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Explanation:
In binomial nomenclature, the scientific name of an organism consists of two parts: the genus name (first part) and the species name (second part). The second part, 'species,' helps differentiate between different organisms within the same genus. This specific naming system is critical for accurate identification and classification of organisms. Hence, the correct answer is 'species.'
Of all the molecules that are significant to biology, which of the following are considered the most important?
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Explanation:
The correct answer is A: Carbohydrates, lipids, proteins, and nucleic acids are considered the most important molecules in biology. Carbohydrates are essential for energy production, lipids play a role in energy storage and cell membrane structure, proteins are involved in various cellular functions, and nucleic acids carry genetic information. While calcium, sulfur, and iron are important elements in biology, they are not considered as primary biological molecules compared to carbohydrates, lipids, proteins, and nucleic acids.
What is the characteristic of the cell membrane consisting of a bilayer of phospholipids with proteins, cholesterol, and glycoproteins that creates a hydrophobic region between two layers of lipids?
Select the best answer.
Explanation:
The correct answer is 'C: Selectively permeable.' The cell membrane is selectively permeable because it allows certain molecules to pass through while restricting the passage of others. The hydrophobic region formed by the lipid bilayer makes it selectively permeable by controlling the movement of substances in and out of the cell. This selective permeability is vital for cellular functions, as it regulates the transport of essential molecules and maintains the internal environment required for proper cell operation and overall cellular homeostasis.
What are the two catabolic pathways that lead to cellular energy production?
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Explanation:
The correct answer is A: Fermentation and cellular respiration. Fermentation and cellular respiration are two catabolic pathways that lead to cellular energy production. Fermentation occurs in the absence of oxygen and involves glycolysis followed by the conversion of pyruvate to various byproducts. Cellular respiration, on the other hand, occurs in the presence of oxygen and involves glycolysis, the citric acid cycle, and the electron transport chain to produce ATP. While fermentation and anaerobic respiration involve partial breakdown of glucose without the complete utilization of oxygen, the term 'internal respiration' is not a commonly used concept in the context of cellular energy production.
Why is DNA important for metabolic activities of the cell?
Select the best answer.
Explanation:
DNA is crucial for metabolic activities as it contains the genetic information needed for the synthesis of enzymes, which are essential for various metabolic reactions within the cell. Enzymes are biological catalysts that regulate and speed up chemical reactions, allowing the cell to carry out necessary metabolic processes efficiently. Therefore, DNA's role in controlling enzyme synthesis directly impacts the cell's metabolic activities, making option D the correct answer.
What is the function of water in photosynthesis?
Select the best answer.
Explanation:
Water plays a crucial role in photosynthesis by supplying electrons in the light reactions of the process. During the light reactions of photosynthesis, water molecules are split, releasing oxygen and providing electrons that are used to drive the production of energy-rich molecules like ATP and NADPH. This electron transfer process is essential for converting light energy into chemical energy, which is then used in the subsequent steps of photosynthesis to produce glucose and other organic compounds.
Among all the molecules significant to biology, which of the following are considered the most important?
Select the best answer.
Explanation:
The correct answer is A: Carbohydrates, lipids, protein, and nucleic acids. These four types of molecules are crucial to biological systems. Carbohydrates provide energy and structural support, lipids serve as energy storage and cell membrane components, proteins have diverse functions in cells, and nucleic acids carry genetic information. While the other choices may have biological importance, nucleic acids play a fundamental role in storing and transmitting genetic information, making them essential in the context of biology.
What is the function of water in photosynthesis?
Select the best answer.
Explanation:
Water is crucial in photosynthesis as it provides electrons during the light reactions. When water molecules are split in the light-dependent reactions, oxygen is released, and electrons are transferred to photosystem II to initiate the electron transport chain. This process is vital for the production of ATP and NADPH, which are necessary for the Calvin cycle to synthesize sugars.
How does a bacterium reproduce?
Select the best answer.
Explanation:
Bacteria reproduce through binary fission, a process in which a single bacterium divides into two identical daughter cells. Mitosis and meiosis are processes specific to eukaryotic cells, not bacteria. Cytokinesis is the final step of the cell cycle where the cytoplasm divides, but it is not the primary reproductive method for bacteria.
What type of bond holds water molecules together?
Select the best answer.
Explanation:
The correct answer is 'Hydrogen.' Water molecules are held together by hydrogen bonds. These bonds form between the slightly positive hydrogen atom of one water molecule and the slightly negative oxygen atom of another water molecule. While hydrogen bonds are weaker than covalent bonds, they play a crucial role in various biological processes, such as the cohesion of water molecules and the unique properties of water as a solvent.
Among all the molecules that are significant to biology, which of the following are considered the most important?
Select the best answer.
Explanation:
The correct answer is A: Carbohydrates, lipids, protein, and nucleic acids. These four types of molecules are essential for various biological processes. Carbohydrates provide energy, lipids are important for energy storage and cell membrane structure, proteins are involved in nearly all cell functions, and nucleic acids carry genetic information. While the other choices contain important components, nucleic acids play a crucial role in storing and transmitting genetic information, making them indispensable in biology.
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