Which of the following does NOT describe enzymes?
Each enzyme is chemically specific.
Some enzymes make up part of the plasma membrane.
Some enzymes are protein plus a cofactor.
Enzymes work by raising the activation energy.
The Correct Answer is D
A. Each enzyme is chemically specific: Enzymes act only on particular substrates due to the unique shape of their active sites. This chemical specificity ensures that metabolic reactions occur in a controlled and precise manner.
B. Some enzymes make up part of the plasma membrane: Enzymes can be embedded in the plasma membrane, where they catalyze reactions such as breaking down extracellular substances or facilitating signal transduction.
C. Some enzymes are protein plus a cofactor: Many enzymes require non-protein helpers, such as metal ions or vitamins, to function effectively. In such cases, the enzyme is described as a holoenzyme, consisting of the protein part (apoenzyme) plus a cofactor.
D. Enzymes work by raising the activation energy: Enzymes actually lower the activation energy needed for reactions, making biochemical processes proceed more efficiently.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is A
Explanation
A. Help in the formation of cell membranes: Lysosomes do not participate in building cell membranes. Their main role is to digest cellular waste, foreign particles, and damaged organelles, not to synthesize structural components like membranes.
B. Digesting particles taken in by endocytosis: Lysosomes contain hydrolytic enzymes that break down materials brought into the cell via endocytosis, helping the cell recycle nutrients and eliminate debris.
C. Degrading worn-out or nonfunctional organelles: Lysosomes perform autophagy, digesting damaged or obsolete organelles to maintain cellular health and prevent accumulation of dysfunctional components.
D. Breaking down bone to release calcium ions into the blood: Specialized lysosomes in osteoclasts secrete enzymes that degrade bone matrix, releasing calcium and phosphate ions into circulation, which is part of normal bone remodeling.
Correct Answer is D
Explanation
A. A static state with no deviation from preset points: Homeostasis does not mean absolute constancy. The body allows for small fluctuations around set points, so a static state without deviation does not reflect the true nature of homeostasis.
B. A dynamic state within an unlimited range, depending on circumstances: While homeostasis is dynamic, the body maintains stability within narrow physiological ranges. Unlimited variation would disrupt vital functions and lead to imbalance or disease.
C. The lowest possible energy usage: Energy conservation is important, but homeostasis is not defined by minimizing energy use. Instead, it involves active processes, many of which require significant energy to maintain internal balance.
D. A relatively stable internal environment, within limits: Homeostasis is best described as the body’s ability to maintain a stable internal environment despite external changes. This stability is achieved within narrow limits, ensuring proper cellular and systemic function.
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