Nokea
What type of molecule forms the cell membrane and controls what enters and exits the cell?
- A. Proteins
- B. Carbohydrates
- C. Lipids
- D. Nucleic acids
Correct Answer: C
Rationale: The cell membrane is primarily composed of lipids, specifically phospholipids, which form a lipid bilayer. This lipid bilayer controls what enters and exits the cell, providing a barrier that is selectively permeable. While proteins are also important components of the cell membrane and play various roles, lipids are the main structural component responsible for the membrane's permeability and function. Carbohydrates and nucleic acids are not the primary components of the cell membrane and do not have the same structural role as lipids.
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Why are negative feedback mechanisms crucial in the endocrine system?
- A. To increase hormone production continuously
- B. To maintain hormone levels within a specific range
- C. To cause a constant release of hormones
- D. To disrupt communication between glands
Correct Answer: B
Rationale: Negative feedback mechanisms in the endocrine system play a vital role in maintaining hormone levels within a specific range. When hormone levels deviate from the set point, negative feedback signals prompt adjustments in hormone production to bring the levels back to the optimal range. This process ensures a delicate balance of hormones in the body, preventing excesses or deficiencies. Choice A is incorrect because continuously increasing hormone production would lead to imbalances. Choice C is incorrect as a constant release of hormones without regulation would disrupt homeostasis. Choice D is incorrect because disrupting communication between glands would hinder proper coordination and regulation of hormone levels, which is essential for the body's overall function.
Which macromolecule serves as the repository of genetic information in all living organisms?
- A. Ribonucleic acid (RNA)
- B. Deoxyribonucleic acid (DNA)
- C. Protein
- D. Carbohydrate
Correct Answer: B
Rationale: - DNA is the macromolecule that serves as the repository of genetic information in all living organisms. It carries the genetic instructions necessary for the growth, development, functioning, and reproduction of organisms.
- RNA (option A) is involved in various cellular processes, including protein synthesis, but DNA is the primary molecule responsible for storing genetic information.
- Proteins (option C) are essential for various cellular functions but do not serve as the primary repository of genetic information.
- Carbohydrates (option D) are important for energy storage and structural support but do not store genetic information.
What is the main function of the small intestine?
- A. To store food and break it down into smaller pieces
- B. To absorb nutrients into the bloodstream
- C. To produce enzymes that help digest food
- D. To eliminate waste products from the body
Correct Answer: B
Rationale: The small intestine is a crucial part of the digestive system responsible for absorbing nutrients into the bloodstream. This absorption primarily occurs through the villi lining the small intestine, which increases the surface area available for nutrient absorption. Nutrients like carbohydrates, proteins, fats, vitamins, and minerals are absorbed into the bloodstream to support various bodily functions such as energy production, growth, and repair. Choices A, C, and D are incorrect as they do not accurately depict the primary function of the small intestine, which is nutrient absorption.
The patella, commonly known as the kneecap, is an example of a:
- A. Sesamoid bone
- B. Long bone
- C. Short bone
- D. Irregular bone
Correct Answer: A
Rationale: The patella, also known as the kneecap, is an example of a sesamoid bone. Sesamoid bones develop within tendons, such as the patellar tendon in this case. The patella is embedded in the tendon of the quadriceps muscle, enhancing the mechanical advantage of the muscle and protecting the knee joint. Long bones, like the femur, are characterized by their elongated shape with growth plates at the ends. Short bones, such as those in the wrist and ankle, are cube-shaped bones. Irregular bones, like vertebrae, do not fit into the other bone shape categories due to their unique shapes and functions.
A spring with a spring constant of 100 N/m is stretched 0.2 m from its equilibrium position. What is the potential energy stored in the spring?
- A. 2 J
- B. 4 J
- C. 8 J
- D. 20 J
Correct Answer: C
Rationale: The potential energy stored in a spring is given by the formula \(PE = \frac{1}{2}kx^2\), where \(k\) is the spring constant and \(x\) is the displacement from the equilibrium position. Substituting the given values, we get \(PE = \frac{1}{2} \times 100 \times (0.2)^2 = 8\) J.