HESI A2 Practice Test Biology

Correct Answer: B

Rationale: The correct answer is B: red blood cell. Red blood cells do not have a nucleus because during their maturation process, they eject their nucleus to make more space for hemoglobin which carries oxygen. Without a nucleus, red blood cells have more space to efficiently transport oxygen throughout the body. Platelets (A), white blood cells (C), and phagocytes (D) all have nuclei as they are involved in various cellular functions that require genetic material and the ability to replicate.

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: 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.

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: B

Rationale: The correct answer is B: Mitochondrion. Mitochondria are known as the powerhouse of the cell due to their role in producing ATP through cellular respiration. This process involves the breakdown of glucose to generate energy in the form of ATP. Mitochondria contain specialized structures such as the inner mitochondrial membrane and ATP synthase that are essential for ATP production. Explanation of why other choices are incorrect: A: Nucleus - The nucleus is responsible for storing genetic material and controlling cell activities but not for ATP production. C: Chloroplast - Chloroplasts are found in plant cells and are responsible for photosynthesis to produce glucose, not ATP. D: Lysosome - Lysosomes are involved in the digestion and recycling of cellular waste, not ATP production.