HESI A2
HESI A2 Biology Practice Test
1. The difference between diploid and haploid is as follows:
- A. Diploid organisms are multicellular
- B. Diploid cells are somatic
- C. Diploid cells have two sets of homologous chromosomes
- D. More than one of the above is true
Correct answer: D
Rationale: Option B correctly states that diploid cells are somatic cells that make up the body tissues and organs in an organism, while haploid cells are gametes involved in sexual reproduction. Option C accurately differentiates diploid and haploid cells based on their chromosome sets – diploid cells have two sets of homologous chromosomes (one from each parent), whereas haploid cells have one set of unpaired chromosomes. Therefore, the correct choice is D, as both statements in options B and C are accurate descriptions of the differences between diploid and haploid cells. Option A is incorrect because diploid and haploid refer to the number of sets of chromosomes in a cell, not whether the organism is multicellular or not.
2. Physical factors such as temperature and pH can alter enzyme activity because they have an effect on the enzyme's ___________.
- A. acidity
- B. shape
- C. chemistry
- D. substrate
Correct answer: B
Rationale: Physical factors such as temperature and pH can alter enzyme activity by affecting the enzyme's shape. Enzymes rely on their specific shapes to function properly and catalyze reactions. Any changes in temperature or pH can disrupt these shapes, causing the enzyme to become denatured and lose its functionality. Therefore, alterations in temperature and pH can impact enzyme activity by directly affecting their shapes. Choices A, C, and D are incorrect because while pH can affect acidity and chemical properties of the enzyme, and temperature can influence the enzyme-substrate interaction, the primary reason for enzyme activity alteration due to temperature and pH is the change in the enzyme's shape.
3. Which is not part of a nucleic acid?
- A. Sulfate
- B. Phosphate
- C. Carbon
- D. Nitrogen
Correct answer: A
Rationale: Sulfate is not part of a nucleic acid. Nucleic acids, such as DNA and RNA, are composed of nucleotide units, which consist of a phosphate group, a sugar molecule (ribose in RNA and deoxyribose in DNA), and a nitrogenous base. Carbon and nitrogen are essential elements found in nucleic acids, while sulfate is not a component of nucleic acid structure. Therefore, the correct answer is A: Sulfate.
4. Which organelle provides storage space for the cell?
- A. Mitochondrion
- B. Vacuole
- C. Cell membrane
- D. Ribosome
Correct answer: B
Rationale: The correct answer is B: Vacuole. The vacuole is the organelle responsible for providing storage space in the cell. It stores water, nutrients, waste products, and other essential materials required by the cell. Vacuoles are crucial for maintaining cell structure and regulating cellular processes. Mitochondrion (choice A) is known as the powerhouse of the cell, responsible for producing energy. The cell membrane (choice C) is a protective barrier around the cell, regulating what enters and exits the cell. Ribosomes (choice D) are involved in protein synthesis, not storage.
5. DNA bases include all but which of the following?
- A. Adenine
- B. Thymine
- C. Uracil
- D. Cytosine
Correct answer: C
Rationale: The correct answer is C: Uracil. Uracil is not a DNA base; it is a base found only in RNA. The four bases in DNA are Adenine, Thymine, Cytosine, and Guanine. Choice A, Adenine, is a correct DNA base. Choice B, Thymine, is a correct DNA base. Choice D, Cytosine, is a correct DNA base. Therefore, Uracil is the only incorrect choice among the options provided.
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