HESI A2
Biology HESI A2 Practice Test
1. Which system maintains the body's balance through the release of hormones directly into the bloodstream?
- A. The gastrointestinal system
- B. The endocrine system
- C. The digestive system
- D. The endocrine system
Correct answer: D
Rationale: The correct answer is D: The endocrine system. The endocrine system maintains the body's balance through the release of hormones directly into the bloodstream. Hormones produced by glands in the endocrine system regulate various bodily functions such as metabolism, growth, and reproduction. This system plays a crucial role in maintaining homeostasis by releasing hormones that help control and coordinate different processes in the body. Choices A, C, and B are incorrect. The gastrointestinal system is responsible for digestion, absorption of nutrients, and excretion of waste; the digestive system includes the gastrointestinal system and other accessory organs; and choice B is a duplicate of the correct answer.
2. During protein synthesis, what process uses an RNA strand to produce a complementary strand of DNA?
- A. Transcription
- B. Translation
- C. Transfer synthesis
- D. Codon synthesis
Correct answer: A
Rationale: The correct answer is 'Transcription.' During transcription, an RNA strand is used to produce a complementary strand of DNA. This process is essential for converting the genetic information stored in DNA into RNA. Choice B, 'Translation,' is incorrect as it involves the synthesis of proteins from mRNA. Choice C, 'Transfer synthesis,' is not a recognized term in molecular biology. Choice D, 'Codon synthesis,' is also incorrect as it does not refer to the process of using an RNA strand to produce a complementary DNA strand.
3. What kind of bond connects sugar and phosphate in DNA?
- A. hydrogen
- B. ionic
- C. covalent
- D. overt
Correct answer: C
Rationale: Sugar and phosphate are indeed connected by covalent bonds in DNA. Covalent bonds involve the sharing of electrons between atoms, which is essential for forming the backbone of the DNA molecule. Hydrogen bonds (Choice A) are important in holding the nitrogenous bases together in the DNA double helix but do not connect sugar and phosphate. Ionic bonds (Choice B) involve the transfer of electrons between atoms and are not the primary bond connecting sugar and phosphate in DNA. 'Overt' (Choice D) is not a type of chemical bond and is an incorrect distractor.
4. Which cell organelle functions to transport materials from the endoplasmic reticulum throughout the cell?
- A. Ribosome
- B. Golgi apparatus
- C. Lysosome
- D. Vacuole
Correct answer: B
Rationale: The Golgi apparatus is the correct answer because it functions to transport materials from the endoplasmic reticulum throughout the cell. Ribosomes are responsible for protein synthesis, not transportation of materials. Lysosomes contain enzymes for digestion and waste removal, not for transporting materials. Vacuoles are primarily involved in storage, waste disposal, and maintaining turgor pressure, not in transporting materials from the endoplasmic reticulum.
5. Which statement is untrue?
- A. RNA is single-stranded.
- B. RNA contains uracil.
- C. DNA codes for proteins.
- D. DNA cannot be altered.
Correct answer: D
Rationale: DNA can be altered through various processes such as mutations, genetic engineering, and epigenetic modifications. Changes in DNA can occur naturally or through external influences, leading to variations in the genetic code. Therefore, the statement that DNA cannot be altered is untrue. Choices A, B, and C are true statements. RNA is indeed single-stranded, RNA contains uracil instead of thymine, and DNA serves as a template for protein synthesis.
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