Nokea
Each species has a characteristic chromosome number and most of their cells have a complete set of these chromosomes. However, in the life cycle of humans, only sperm and eggs have which number of chromosomes?
- A. Diploid.
- B. Polyploid.
- C. Haploid.
- D. Monoploid.
Correct Answer: C
Rationale:
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Which hormone is produced by the pineal gland?
- A. insulin
- B. testosterone
- C. melatonin
- D. epinephrine
Correct Answer: C
Rationale: The correct answer is melatonin (Choice C). The pineal gland is responsible for producing melatonin, a hormone that regulates sleep-wake cycles. Insulin (Choice A) is produced by the pancreas and regulates blood sugar levels. Testosterone (Choice B) is primarily produced by the testes in males and in smaller amounts by the ovaries in females. Epinephrine (Choice D) is produced by the adrenal glands and is involved in the body's fight-or-flight response.
Which of the following nucleotides is not a component of DNA?
- A. Adenine
- B. Thymine
- C. Uracil
- D. Cytosine
Correct Answer: C
Rationale: The four nucleotides that make up DNA are Adenine, Thymine, Cytosine, and Guanine. Uracil is a nucleotide base that is present in RNA but not in DNA. Therefore, Uracil is the correct answer as it is not a component of DNA.
What structure in a plant cell is surrounded by a double membrane and contains most of the genetic information used to control the cell?
- A. Mitochondrion
- B. Nucleus.
- C. Chromatin.
- D. Chromosome.
Correct Answer: B
Rationale: Rationale: The correct answer is B: Nucleus. The nucleus is surrounded by a double membrane and contains most of the genetic information in the form of DNA, which controls the cell's activities. Mitochondria (A) are involved in energy production, chromatin (C) is a complex of DNA and proteins within the nucleus, and chromosomes (D) are condensed structures of DNA found in the nucleus during cell division. Therefore, the nucleus is the structure that fits the description provided in the question.
Which cellular component 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 cell membrane is responsible for protecting the cell, facilitating communication with the external environment, and controlling the passage of substances into and out of the cell. It acts as a barrier, regulating the entry and exit of molecules to maintain the cell's internal environment. The nucleus, endoplasmic reticulum, and cytoplasm have their own distinct functions within the cell but do not primarily serve the purposes mentioned in the question.
Which characteristic is true of prokaryotic cells?
- A. Have a nucleus
- B. Have a capsule
- C. Have membrane-bound organelles
- D. Cannot move on their own
Correct Answer: B
Rationale: Prokaryotic cells are characterized by the absence of a nucleus; instead, they have a nucleoid region where the genetic material is located. Prokaryotic cells often have a capsule, a protective layer outside the cell wall that plays a role in protection and adherence to surfaces. While eukaryotic cells have membrane-bound organelles, prokaryotic cells lack these membrane-bound structures. Prokaryotic cells are capable of movement, facilitated by structures like flagella or pili.