Biology HESI A2 Practice Test

Correct Answer: C

Rationale: Exocytosis is the process by which cells expel waste products out of the cell. It is essential for maintaining cellular homeostasis and preventing the accumulation of toxic substances. Through exocytosis, cells can remove waste such as by-products of metabolism or harmful substances. This process helps keep the cell environment clean and functional. A: Cells obtain energy through processes like cellular respiration, not exocytosis. B: Cells defend against invaders through immune responses, not exocytosis. D: Cell division occurs through processes like mitosis, not exocytosis.

Correct Answer: B

Rationale: The correct answer is B: heterozygous. In a heterozygous situation, an individual carries two different alleles for a particular gene, resulting in different forms of the allele. This creates genetic diversity and can lead to varying phenotypic expressions. The term phenotype (A) refers to the physical characteristics of an organism, not specifically related to different forms of alleles. Homolog (C) refers to chromosomes that are similar in structure and function but not necessarily different forms of alleles. Homozygous (D) describes a situation where an individual carries two identical alleles for a gene, which does not involve different forms of alleles.

Correct Answer: B

Rationale: The correct answer is B: They are haploid cells. Gametes are sex cells (sperm and egg) that contain half the number of chromosomes as somatic cells. This is essential for maintaining the diploid chromosome number during fertilization. Choice A is incorrect because gametes are not diploid, but haploid. Choice C is incorrect because gametes are not somatic cells; somatic cells make up the body tissues and are diploid. Choice D is incorrect because only choice B is true; gametes are haploid, not diploid or somatic.

Correct Answer: C

Rationale: The correct answer is C: epididymis. The epididymis is the structure in the male reproductive system that stores spermatozoa during the maturation process. Sperm are produced in the testes and then move to the epididymis for storage and maturation before being ejaculated. The vas deferens is the tube that carries mature sperm from the epididymis to the urethra during ejaculation. The scrotum is the external sac that holds the testes and helps regulate their temperature. The testicular artery supplies blood to the testes but is not directly involved in storing spermatozoa.

Correct Answer: C

Rationale: The correct answer is C because molecules move from areas of high concentration to low concentration through a process called passive diffusion, which does not require energy. This movement occurs to reach equilibrium. Choice A is incorrect as some molecules can pass through cell membranes using channels or transporters. Choice B is incorrect because molecules move from high to low concentration in passive transport. Choice D is incorrect because molecules are constantly moving due to various forces.