HESI A2
HESI A2 Biology 2024
1. Which molecules contain only carbon, hydrogen, and oxygen?
- A. Lipids and proteins
- B. Carbohydrates and lipids
- C. Proteins and carbohydrates
- D. Nucleic acids and proteins
Correct answer: B
Rationale: Carbohydrates and lipids are the molecules that contain only carbon, hydrogen, and oxygen. Carbohydrates such as sugars and starches are made up of carbon, hydrogen, and oxygen in a ratio of 1:2:1, while lipids such as fats and oils are composed of carbon, hydrogen, and oxygen as well. Lipids typically contain more carbon and hydrogen atoms compared to oxygen atoms. Proteins contain nitrogen in addition to carbon, hydrogen, and oxygen, while nucleic acids contain phosphorus in addition to carbon, hydrogen, and oxygen. Therefore, choices A, C, and D are incorrect as they include molecules that contain elements other than carbon, hydrogen, and oxygen.
2. What is the fundamental unit of life?
- A. Atom
- B. Cell
- C. Tissue
- D. Organ
Correct answer: B
Rationale: The correct answer is 'B: Cell.' Cells are indeed the fundamental unit of life as they are responsible for all living functions, including growth, reproduction, and maintaining homeostasis. While atoms are the basic building blocks of matter, cells are the smallest structural and functional unit of living organisms. Choices C and D, tissue and organ respectively, are composed of multiple cells working together and are not considered the basic unit of life.
3. Which system maintains the body's balance through the release of hormones directly into the bloodstream?
- A. The gastrointestinal system
- B. The endocrine system
- C. The digestive system
- D. The endocrine system
Correct answer: D
Rationale: The correct answer is D: The endocrine system. The endocrine system maintains the body's balance through the release of hormones directly into the bloodstream. Hormones produced by glands in the endocrine system regulate various bodily functions such as metabolism, growth, and reproduction. This system plays a crucial role in maintaining homeostasis by releasing hormones that help control and coordinate different processes in the body. Choices A, C, and B are incorrect. The gastrointestinal system is responsible for digestion, absorption of nutrients, and excretion of waste; the digestive system includes the gastrointestinal system and other accessory organs; and choice B is a duplicate of the correct answer.
4. Which of these molecules contains glucose?
- A. Proteins
- B. Lipids
- C. Nucleic acids
- D. Carbohydrates
Correct answer: D
Rationale: Glucose is a type of simple sugar and is classified as a carbohydrate. It is commonly found in various carbohydrate-containing foods such as fruits, vegetables, grains, and sugary snacks. Therefore, the molecule containing glucose would be a carbohydrate, making choice D the correct answer. Proteins (choice A) are made up of amino acids, lipids (choice B) are fats, and nucleic acids (choice C) are DNA and RNA, none of which contain glucose.
5. How should a researcher test the hypothesis that eating chocolate leads to acne in teenagers?
- A. Take 100 teenagers and feed each one a different amount of chocolate daily for 60 days; then test for acne.
- B. Take 100 teenagers and feed 50 two bars of chocolate daily for 60 days while the other 50 eat no chocolate; then test for acne.
- C. Take 1 teenager and feed him or her two bars of chocolate for 30 days and no chocolate for 30 days; then test for acne.
- D. Take 100 teenagers and feed them no chocolate for 30 days and two bars of chocolate apiece for 30 days; then test for acne.
Correct answer: B
Rationale: Option B is the correct approach to test the hypothesis that eating chocolate leads to acne in teenagers. This method involves having a control group (50 teenagers not consuming chocolate) and an experimental group (50 teenagers consuming two bars of chocolate daily), which allows for comparison. By having two distinct groups, researchers can assess the impact of chocolate consumption on acne development. Option A lacks a control group for comparison, making it harder to attribute any observed effects specifically to chocolate consumption. Option C only involves a single subject, which limits the generalizability of the results. Option D, where all teenagers experience both conditions, does not allow for a direct comparison between chocolate consumption and acne development, as all subjects are exposed to both conditions.
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