HESI A2 Practice Test Biology

Correct Answer: A

Rationale: The correct answer is A because tRNA carries amino acids to the ribosome during protein synthesis. Firstly, tRNA molecules bind to specific amino acids through their anticodon region. Secondly, tRNA recognizes the mRNA codon at the ribosome, ensuring the correct amino acid is added to the growing polypeptide chain. This process is crucial for translating the genetic code into proteins. Choices B, C, and D are incorrect because tRNA does not link nucleotides together, copy DNA sequences, or replicate genetic material during protein synthesis.

Correct Answer: C

Rationale: The correct answer is C: ribosome. Ribosomes are the organelles responsible for organizing protein synthesis. They are the site where proteins are assembled based on instructions from the cell's DNA. Ribosomes can be found in the cytoplasm and on the endoplasmic reticulum. Mitochondria (A) are responsible for energy production, the nucleus (B) contains genetic material but does not directly organize protein synthesis, and vacuoles (D) are primarily involved in storage and maintaining cell structure. Therefore, the ribosome is the only organelle directly involved in protein synthesis among the choices provided.

Correct Answer: A

Rationale: The correct answer is A because DNA contains the genetic information needed for the synthesis of enzymes, which are crucial for metabolic activities in the cell. Enzymes are proteins that catalyze chemical reactions within the cell, allowing essential metabolic processes to occur. DNA serves as a template for the production of specific enzymes through the process of transcription and translation. Choices B, C, and D are incorrect because DNA does not directly play a role in stabilizing the cell wall, initiating cell division, or preventing diffusion of nutrients. These processes are regulated by other cellular components and mechanisms.

Correct Answer: A

Rationale: Transcription is the correct answer because it is the process where RNA is synthesized from a DNA template. It involves RNA polymerase binding to the DNA template and creating a complementary RNA strand by matching RNA nucleotides to the DNA template. Translation is incorrect as it involves the synthesis of proteins from mRNA. Transformation is a process in genetics unrelated to protein synthesis. Replication is the process of copying DNA to create two identical DNA molecules, not RNA synthesis from DNA.

Correct Answer: C

Rationale: The correct answer is C: four. DNA is composed of four different types of nucleotides: adenine (A), thymine (T), cytosine (C), and guanine (G). Each nucleotide consists of a nitrogenous base, a sugar (deoxyribose), and a phosphate group. These four nucleotides form complementary base pairs, which are essential for DNA replication and protein synthesis. The other choices are incorrect because DNA is made up of multiple nucleotides with specific base pairings, not just one or two types. Therefore, the correct answer is C: four.