how many different types of nucleotides are there in dna
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HESI A2

HESI A2 Practice Test Biology

1. How many different types of nucleotides are there in DNA?

Correct answer: C

Rationale: The correct answer is 'C: four.' DNA is composed of four different types of nucleotides: adenine, thymine, guanine, and cytosine. These nucleotides pair up in specific combinations to form the genetic code. Choices 'A: one,' 'B: two,' and 'D: eight' are incorrect because DNA consists of a set of four distinct nucleotides, not one, two, or eight.

2. Which of the following is true of the Krebs cycle?

Correct answer: B

Rationale: The Krebs cycle, also known as the citric acid cycle, involves a series of redox reactions that occur in the mitochondria. The cycle begins with the oxidation of acetyl CoA, which is derived from the breakdown of sugars produced during glycolysis. These sugars are broken down further in the Krebs cycle to produce ATP and reduce electron carriers such as NADH and FADH2. The cycle does not involve proteins produced during glycolysis. Protons are not passed along a gradient to produce ATP directly in the Krebs cycle; rather, they are used in the electron transport chain to generate ATP. The Krebs cycle is not known as the glycolic acid cycle; glycolysis is the metabolic pathway that produces pyruvate from glucose.

3. Which of the following are found both in open and closed circulatory systems?

Correct answer: C

Rationale: The correct answer is C, Capillaries. Capillaries are found in both open and closed circulatory systems. Capillaries are small blood vessels that connect arteries and veins, allowing for the exchange of nutrients and wastes between the blood and tissues. They are essential components of circulatory systems regardless of whether they are open or closed. Arteries (Choice A) are not found in open circulatory systems, as these systems lack distinct arteries and veins. Red blood cells (Choice B) are present in the blood but are not exclusive to either open or closed circulatory systems. Immune cells (Choice D) are not specific components of circulatory systems, as they are part of the immune system.

4. A pencil measures 8cm long. What is this in mm?

Correct answer: A

Rationale: To convert centimeters to millimeters, you need to multiply by 10 since 1 centimeter is equal to 10 millimeters. Therefore, 8 cm x 10 mm/cm = 80 mm. The pencil measures 8 cm, which is equivalent to 80 mm when converted. Choice A is correct as it correctly converts 8 cm to mm by multiplying it by 10. Choices B, C, and D are incorrect because they do not apply the correct conversion factor.

5. What is the role of ribosomes in the cell?

Correct answer: C

Rationale: The correct answer is C: Synthesize proteins. Ribosomes are responsible for protein synthesis by linking amino acids together. Choice A is incorrect because ribosomes do not break down cellular waste. Choice B is incorrect as ribosomes do not organize cellular division. Choice D is incorrect because ribosomes do not provide cellular structure.

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