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. Express 25 as a fraction in lowest terms.
- A. 1⅖
- B. 1½
- C. 1¼
- D.
Correct answer: C
Rationale: To express 25 as a fraction in lowest terms, we write it as 25/1. Then, we simplify the fraction by dividing both the numerator and denominator by their greatest common divisor, which is 25. This results in 25/1 = 25/25 = 1 as the whole number part and 0 as the fractional part. Thus, 25 can be expressed as 1¼. Choice A (1⅖) is incorrect as it represents 1 and 2/5, which is not equivalent to 25. Choice B (1½) is incorrect as it represents 1 and 1/2, which is also not equivalent to 25. Choice D is empty and does not provide an answer.
3. What is your “funny bone” actually?
- A. Humerus
- B. Ulnar nerve
- C. Carpal bone
- D. Biceps brachii
Correct answer: B
Rationale: Your 'funny bone' is actually your ulnar nerve, not a bone. The ulnar nerve runs along the inside part of your elbow and is easily bumped or compressed, leading to a tingling or slightly painful sensation that is commonly referred to as hitting your funny bone. The humerus (Choice A) is the long bone in your upper arm, the carpal bone (Choice C) is a bone in your wrist, and the biceps brachii (Choice D) is a muscle in your upper arm. Therefore, the correct answer is the ulnar nerve (Choice B).
4. Which part of the brain is responsible for regulating breathing and heart rate?
- A. Cerebrum
- B. Medulla oblongata
- C. Cerebellum
- D. Hypothalamus
Correct answer: B
Rationale: The correct answer is the Medulla oblongata. This structure, located in the brainstem, plays a crucial role in regulating essential functions such as breathing, heart rate, and blood pressure. It serves as a control center for autonomic functions necessary for maintaining life. The Cerebrum (Choice A) is mainly responsible for higher brain functions such as thinking and voluntary movements, not for regulating basic physiological processes like breathing and heart rate. The Cerebellum (Choice C) is involved in coordination, balance, and muscle control, but not in regulating breathing and heart rate. The Hypothalamus (Choice D) plays a role in regulating body temperature, hunger, and thirst, but it is not primarily responsible for controlling breathing and heart rate.
5. Which substance forms hydroxide ions when placed in water?
- A. Lemon juice
- B. Battery acid
- C. Vinegar
- D. Lye
Correct answer: D
Rationale: The correct answer is D, lye. Lye, also known as sodium hydroxide (NaOH), is a strong base that forms hydroxide ions (OH-) when placed in water. When lye dissolves in water, it dissociates into sodium ions (Na+) and hydroxide ions, making it an alkaline substance. Lemon juice, battery acid, and vinegar do not form hydroxide ions when placed in water. Lemon juice contains citric acid, battery acid contains sulfuric acid, and vinegar contains acetic acid, none of which produce hydroxide ions when dissolved in water.
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