anaerobic respiration happens in because

HESI A2

HESI A2 Biology Practice Test

1. Anaerobic respiration happens in _ because _ .

A. Animals; they need energy
B. Plants; they use sunlight
C. Bacteria; they live in environments with low oxygen
D. None of the above

Correct answer: C

Rationale: Anaerobic respiration happens in bacteria because they live in environments with low oxygen. Bacteria, unlike animals and plants, do not have easy access to oxygen for aerobic respiration and must find alternative ways to produce energy to survive. This makes anaerobic respiration essential for their metabolic processes. Choice A is incorrect because although animals need energy, they generally rely on aerobic respiration when oxygen is available. Choice B is incorrect because plants primarily perform photosynthesis using sunlight to produce energy. Choice D is incorrect as anaerobic respiration does occur in specific organisms like bacteria when oxygen is scarce.

2. Which is not part of a nucleic acid?

A. Sulfate
B. Phosphate
C. Carbon
D. Nitrogen

Correct answer: A

Rationale: Sulfate is not part of a nucleic acid. Nucleic acids, such as DNA and RNA, are composed of nucleotide units, which consist of a phosphate group, a sugar molecule (ribose in RNA and deoxyribose in DNA), and a nitrogenous base. Carbon and nitrogen are essential elements found in nucleic acids, while sulfate is not a component of nucleic acid structure. Therefore, the correct answer is A: Sulfate.

3. Cytosine and thymine are known as:

A. Purines
B. Pyrimidines
C. Both
D. None of the above

Correct answer: B

Rationale: Cytosine and thymine are known as pyrimidines because they have a single carbon ring structure. Purines, on the other hand, have a double-ring structure. Choice A ('Purines') is incorrect because purines have a double-ring structure, unlike cytosine and thymine. Choice C ('Both') is incorrect as it implies they are both purines and pyrimidines, which is not true. Choice D ('None of the above') is incorrect because cytosine and thymine are indeed pyrimidines.

4. Which cells in the human body lack nuclei?

A. Nerve cells
B. Red blood cells
C. Liver cells
D. Connective tissue cells

Correct answer: B

Rationale: Red blood cells, also known as erythrocytes, lack nuclei in humans. This absence of a nucleus allows more space for hemoglobin, the protein responsible for carrying oxygen, making red blood cells efficient at their function of oxygen transport in the body. Nerve cells (Choice A), liver cells (Choice C), and connective tissue cells (Choice D) all possess nuclei as they require genetic material for their functions, such as cell signaling, protein synthesis, and structural support.

5. Which component of the cell contributes to the protection, communication, and passage of substances into and out of the cell?

A. Nucleus
B. Cell membrane
C. Endoplasmic reticulum
D. Cytoplasm

Correct answer: B

Rationale: The correct answer is the cell membrane. The cell membrane is responsible for protecting the cell, facilitating communication with the external environment, and regulating the passage of substances into and out of the cell. The nucleus (Choice A) is the control center of the cell and houses the genetic material but is not primarily involved in these functions. The endoplasmic reticulum (Choice C) is involved in protein synthesis and lipid metabolism, not primarily in protection or communication. The cytoplasm (Choice D) is the gel-like substance that fills the cell but does not specifically contribute to protection, communication, or substance passage.