HESI A2
Biology HESI A2 Practice Exam
1. Most enzymes are made up of what?
- A. proteins
- B. lipids
- C. starches
- D. simple sugars
Correct answer: A
Rationale: Most enzymes are made up of proteins. Proteins are large biomolecules composed of amino acids that are vital for the structure and function of enzymes. Enzymes act as catalysts in biochemical reactions, speeding up the rate of chemical reactions in living organisms. They exhibit high specificity and efficiency due to their unique protein structures. Lipids, starches, and simple sugars are not typically the primary components of enzymes, making them incorrect choices.
2. Select the strand of DNA that would match this segment: ACTTGCA
- A. TGAACGT
- B. GACCATG
- C. ACTTGCA
- D. None of the above
Correct answer: A
Rationale: The correct match for the DNA segment ACTTGCA is TGAACGT. In DNA, adenine (A) always pairs with thymine (T), and cytosine (C) always pairs with guanine (G). Therefore, the complementary strand to ACTTGCA should be TGAACGT, making choice A the correct answer. Choice B (GACCATG) does not follow the base pairing rules; hence, it is incorrect. Choice C (ACTTGCA) is the original segment, not its complementary strand. Choice D is incorrect as well because a matching strand does exist.
3. How does yeast reproduce?
- A. Binary fission
- B. Spore formation
- C. Budding
- D. Cloning
Correct answer: C
Rationale: Yeast typically reproduces through a process called budding. During budding, a small outgrowth forms on the parent yeast cell, gradually enlarging in size until it separates to become a new, genetically identical daughter cell. This method of reproduction allows yeast to rapidly multiply and grow in favorable conditions. It is different from binary fission, spore formation, and cloning. Binary fission involves the division of a single organism into two genetically identical organisms. Spore formation is a method seen in certain fungi where specialized cells develop into spores for reproduction. Cloning involves producing genetically identical copies of an organism. Therefore, budding is the correct answer for how yeast reproduces.
4. Which gives the order of four taxonomic categories from least to most specific?
- A. Kingdom, phylum, class, order
- B. Kingdom, phylum, order, class
- C. Kingdom, order, phylum, class
- D. Kingdom, class, order, phylum
Correct answer: A
Rationale: The correct order of the four taxonomic categories from least to most specific is Kingdom, phylum, class, and order. This sequence adheres to the hierarchical system of classification where organisms are grouped based on shared characteristics, becoming more specific as you move from Kingdom to order. Choice B is incorrect as the order of 'order' and 'class' is swapped. Choice C is incorrect as 'order' precedes 'phylum' instead of following it. Choice D is incorrect as 'class' should come before 'order'.
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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