Nokea
Which of the following statements about enzymes is not true?
- A. They catalyze reactions
- B. They raise the activation energy needed
- C. They have an active site
- D. They are typically proteins
Correct Answer: B
Rationale: Enzymes function to catalyze reactions by lowering the activation energy required for the reaction to occur. Therefore, the statement that enzymes raise the activation energy needed is incorrect. Enzymes have an active site where substrates bind and undergo catalysis. Enzymes are typically proteins that act as biological catalysts.
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Which of the following cell types lacks a nucleus?
- A. platelet
- B. red blood cell
- C. white blood cell
- D. phagocyte
Correct Answer: B
Rationale: The correct answer is red blood cell (choice B). Red blood cells, also known as erythrocytes, lack a nucleus at maturity in humans. The absence of a nucleus allows these cells to carry oxygen more efficiently by maximizing space for hemoglobin, the oxygen-carrying protein. Platelets (choice A), white blood cells (choice C), and phagocytes (choice D) all have nuclei. Platelets are involved in blood clotting, white blood cells are part of the immune system, and phagocytes specialize in engulfing and digesting cellular debris and pathogens.
Why is DNA crucial for the metabolic activities of the cell?
- A. It initiates cellular mitosis.
- B. It provides cell wall stability.
- C. It increases glucose absorption.
- D. It controls the synthesis of enzymes.
Correct Answer: D
Rationale: DNA is crucial for the metabolic activities of the cell because it contains the genetic information necessary to regulate the synthesis of enzymes. Enzymes are essential for catalyzing biochemical reactions involved in metabolic processes within the cell. DNA controls the production of enzymes, which are vital for driving various metabolic pathways. Therefore, the correct answer is D, as DNA's role in controlling enzyme synthesis is fundamental for the cell's metabolic activities.
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 term best describes the sum of all an organism's chemical processes?
- A. Respiration.
- B. Anabolism.
- C. Metabolism.
- D. Differentiation.
Correct Answer: C
Rationale: The correct answer is C: Metabolism. Metabolism refers to the sum of all chemical processes in an organism to maintain life. It includes both anabolism (building up molecules) and catabolism (breaking down molecules). Respiration (A) is a specific part of metabolism involving the breakdown of glucose to produce energy. Anabolism (B) is the process of building complex molecules from simpler ones. Differentiation (D) is the process in which cells become specialized for specific functions, not related to the sum of all chemical processes in an organism. Therefore, metabolism is the most appropriate term to describe the overall chemical processes in an organism.
A pencil measures 8 cm long. What is this length in mm?
- A. 80 mm
- B. 800 mm
- C. 8 mm
- D. 0.8 mm
Correct Answer: A
Rationale: To convert centimeters to millimeters, you multiply by 10 since there are 10 millimeters in 1 centimeter. Therefore, 8 cm x 10 = 80 mm. The correct answer is 80 mm.