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What does the mitochondrion produce that causes it to often be called the powerhouse of the cell?
- A. ATP
- B. Enzymes.
- C. Proteins.
- D. DNA.
Correct Answer: A
Rationale:
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What molecules are unmetabolized by the body, but are used to increase reaction rates?
- A. Sugars.
- B. Proteins.
- C. Enzymes.
- D. Lipids.
Correct Answer: C
Rationale: The correct answer is C: Enzymes. Enzymes are molecules that increase reaction rates by acting as catalysts in biochemical reactions. They are not metabolized by the body, meaning they remain unchanged after facilitating the reactions. Sugars (choice A), proteins (choice B), and lipids (choice D) are all metabolized by the body to provide energy or building blocks for various cellular functions, unlike enzymes which remain unchanged. Therefore, enzymes are the only choice that fits the description of being unmetabolized molecules used to increase reaction rates.
Select the two bases that are purines:
- A. A
- B. C
- C. T
- D. N
Correct Answer: A
Rationale: Purines are adenine (A) and guanine (G), which are the larger nitrogenous bases found in DNA and RNA. Adenine (A) is one of the purine bases, whereas cytosine (C) and thymine (T) are pyrimidines. Therefore, the correct answer is A. Option D, 'N,' is not a purine base.
In a phospholipid, the head:
- A. Is hydrophilic
- B. Is hydrophobic
- C. Faces the outer side of the layer
- D. Both A and C
Correct Answer: D
Rationale: The head of a phospholipid is hydrophilic, meaning it is water-loving, and faces the outer side of the lipid bilayer. This arrangement allows the hydrophilic head to interact with water while the hydrophobic tails are shielded from it. Therefore, option D, 'Both A and C,' is the correct answer as the head is hydrophilic and faces the outer side of the layer.
Human cells need oxygen for respiration. What system of the body is responsible for transporting an oxygen molecule to different locations throughout the body?
- A. Skeletal
- B. Lymphatic
- C. Circulatory
- D. Respiratory
Correct Answer: C
Rationale: The circulatory system is responsible for transporting oxygen throughout the body. It consists of the heart, blood vessels, and blood, which work together to deliver oxygen from the lungs to cells and tissues, facilitating cellular respiration. The skeletal system provides structural support and protection for the body but is not involved in oxygen transport. The lymphatic system helps maintain fluid balance and immune function, not oxygen transport. The respiratory system is responsible for gas exchange in the lungs but relies on the circulatory system to transport oxygen to cells and tissues.
What part of a plant cell acts as a barrier and provides support to the cell?
- A. cell membrane.
- B. Xylem.
- C. chloroplast
- D. Cell wall.
Correct Answer: D
Rationale: