HESI A2
HESI A2 Biology 2024
1. Which organelle is found in protists but not in monerans?
- A. Golgi apparatus
- B. Chromosome
- C. Cytoplasm
- D. Cell membrane
Correct answer: A
Rationale: The Golgi apparatus is the correct answer. The Golgi apparatus is a cellular organelle responsible for processing and packaging proteins before they are transported to their final destination. Protists, being eukaryotic organisms, have membrane-bound organelles including the Golgi apparatus, which are absent in monerans. Monerans are prokaryotic organisms that lack membrane-bound structures such as the Golgi apparatus. Choices B, C, and D are incorrect as chromosomes, cytoplasm, and cell membranes are present in both protists and monerans.
2. The phases of mitosis include:
- A. Prophase, interphase, metaphase, anaphase, and telophase
- B. Prophase, prophase, metaphase, anaphase, and cytokinesis
- C. Prophase, prometaphase, metaphase, anaphase, and telophase
- D. Prophase, interphase, prophase, anaphase, and telophase
Correct answer: C
Rationale: The correct phases of mitosis are prophase, prometaphase, metaphase, anaphase, and telophase. Prophase is the first phase where chromatin condenses into chromosomes, the nuclear envelope breaks down, and the mitotic spindle forms. Prometaphase follows prophase, involving the full disintegration of the nuclear envelope and the attachment of spindle fibers to the kinetochores of the chromosomes. Metaphase is where chromosomes align along the metaphase plate. Anaphase is the phase where sister chromatids separate and move towards opposite poles. Telophase marks the final stage of mitosis, involving the decondensation of chromosomes and the reformation of the nuclear envelope. Choice A is incorrect because it includes interphase, which is not a phase of mitosis. Choice B is incorrect as it repeats prophase, which is the initial phase. Choice D is incorrect because it includes interphase and repeats prophase.
3. Which of the following shows how information is transformed to make a protein?
- A. DNA-RNA-protein
- B. gene-chromosome-protein
- C. ATP-amino acid-protein
- D. RNA-DNA-protein
Correct answer: A
Rationale: The correct sequence of events for protein synthesis is that DNA is transcribed into RNA, which is then translated into a protein. This process is known as the central dogma of molecular biology. In this sequence, DNA serves as the template for RNA synthesis (transcription), and the RNA serves as the template for protein synthesis (translation). Choice B is incorrect as genes are segments of DNA that code for proteins, and chromosomes are structures that contain DNA. Choice C is incorrect as ATP is an energy molecule and amino acids are the building blocks of proteins, but they are not directly involved in the synthesis process. Choice D is incorrect because RNA is first transcribed from DNA and then used as a template to produce proteins.
4. 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.
5. Why do high-salt content foods not require refrigeration to prevent spoilage?
- A. Osmosis
- B. Diffusion
- C. Active transport
- D. Passive transport
Correct answer: A
Rationale: Osmosis is the natural process that prevents high-salt content foods from spoiling without the need for refrigeration. Osmosis involves the movement of water across a semi-permeable membrane from an area of lower solute concentration (water) to an area of higher solute concentration (salt). In high-salt content foods, the salt acts as a preservative by drawing moisture out of bacteria or other microorganisms, making it difficult for them to survive and spoil the food. This process helps in preserving the food and preventing spoilage even without refrigeration. Choices B, C, and D are incorrect because they do not involve the specific mechanism of water movement in response to the salt concentration in high-salt content foods.
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