HESI A2
HESI A2 Biology Practice Test
1. Which of the following bases is not present in RNA?
- A. Adenine
- B. Thymine
- C. Uracil
- D. Cytosine
Correct answer: B
Rationale: Thymine is not present in RNA. RNA uses uracil as one of its bases, which pairs with adenine. In RNA, adenine does not pair with thymine as in DNA. Cytosine and guanine are the other two bases found in both RNA and DNA.
2. Bacillus subtilis may be described as ___________.
- A. spiral
- B. globular
- C. rod-shaped
- D. grape-like clusters
Correct answer: C
Rationale: Bacillus subtilis is a rod-shaped bacterium. Its name "Bacillus" refers to its rod-like shape, which is a characteristic feature of this bacteria.
3. Which is true of the term Phenotype?
- A. It is the genetic code
- B. Phenotype determines genotype
- C. Genotype determines phenotype
- D. Genotype, epigenetic factors, and environmental factors determine phenotype
Correct answer: D
Rationale: The term "phenotype" refers to the observable characteristics or traits of an organism, which are determined by a combination of genotype (genetic makeup), epigenetic factors (modifications to gene expression), and environmental factors (external influences and experiences). Genotype, epigenetic factors, and environmental factors all play a role in determining an individual's phenotype, making option D the correct statement. Options A, B, and C are incorrect because the phenotype is not the genetic code, the phenotype does not determine the genotype, and it is the genotype that influences the phenotype, not the other way around.
4. Which of the following organelles is responsible for producing ATP in cells?
- A. Nucleus
- B. Mitochondrion
- C. Chloroplast
- D. Lysosome
Correct answer: B
Rationale: The correct answer is 'Mitochondrion.' Mitochondria are known as the powerhouse of the cell and are responsible for producing ATP, the energy currency of the cell. The nucleus is responsible for storing genetic material and controlling cell activities, not for ATP production. Chloroplasts are found in plant cells and are responsible for photosynthesis, not ATP production. Lysosomes are involved in digestion and waste removal, not ATP production.
5. What is necessary for active transport through a membrane to take place?
- A. Glucose
- B. Oxygen
- C. Sodium
- D. ATP
Correct answer: D
Rationale: Active transport through a membrane requires energy in the form of ATP (adenosine triphosphate). ATP provides the necessary energy for the transport proteins to move molecules against the concentration gradient, from an area of lower concentration to higher concentration. This process is essential for maintaining cellular functions and regulating the internal environment of a cell. Glucose, oxygen, and sodium are important molecules involved in various cellular processes, but they are not the primary energy source required for active transport across membranes. Therefore, the correct answer is ATP.
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