HESI A2 Practice Test Biology

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: D

Rationale: The correct answer is D: Nucleus. The nucleus contains the genetic material of the cell, which is stored in the form of DNA. It controls the cell's activities and serves as the command center. The Golgi apparatus (A) is involved in processing and packaging proteins, the ribosome (B) is responsible for protein synthesis, and the endoplasmic reticulum (C) is involved in protein synthesis and lipid metabolism. The nucleus is unique in its role as the organelle that houses the cell's genetic information.

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.

Correct Answer: C

Rationale: The correct answer is C: Synthesize proteins. Ribosomes are responsible for protein synthesis in the cell by translating mRNA into specific amino acid sequences. They are composed of rRNA and protein subunits. Ribosomes do not break down cellular waste (A), organize cellular division (B), or provide cellular structure (D). Cellular waste breakdown is typically performed by lysosomes, cellular division is organized by the centrosome, and cellular structure is maintained by the cytoskeleton.

Correct Answer: A

Rationale: The correct answer is A: Phospholipids. Phospholipids are essential components of the plasma membrane due to their amphipathic nature, with hydrophilic heads and hydrophobic tails. This structure allows phospholipids to form a lipid bilayer, creating a barrier that separates the internal and external environments of the cell. Steroids (B) are not a major component of the plasma membrane. Sugars (C) are found in glycoproteins and glycolipids on the membrane surface, but they are not the main structural component. Amino acids (D) are the building blocks of proteins, which can be membrane proteins, but they are not the key structural component of the membrane itself.