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If a hard-boiled egg is placed in a beaker of saltwater, what will happen to the egg?
- A. Expand because water will move into the egg
- B. Shrivel because water will leave the egg
- C. Remain the same
- D. None of the above
Correct Answer: B
Rationale: When a hard-boiled egg is placed in a beaker of saltwater, the egg will shrivel because water will move out of the egg due to osmosis. Osmosis is the movement of water across a semipermeable membrane from an area of lower solute concentration to an area of higher solute concentration. In this case, the saltwater has a higher solute concentration than the egg, causing water to move out of the egg, leading to shrinkage or shriveling.
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A child is sick. They have a body temperature that exceeds 37Å—C. The body senses this and begins to sweat in order to lower the temperature. What is this an example of?
- A. Positive feedback loop
- B. Negative feedback loop
- C. Both
- D. None of the above
Correct Answer: B
Rationale: This scenario describes a negative feedback loop. In negative feedback, the body's response works to reverse the initial stimulus, in this case, sweating to lower the elevated body temperature. This mechanism helps maintain homeostasis by regulating the body's temperature back to the normal range.
Which genetic descriptor refers to an organism's actual appearance?
- A. Phenotype
- B. Genotype
- C. Homozygote
- D. Karyotype
Correct Answer: A
Rationale: Phenotype refers to the observable characteristics or traits of an organism, including physical appearance, behavior, and physiological properties. It is influenced by the organism's genotype and environmental factors. Genotype, on the other hand, represents the genetic makeup of an organism, while homozygote refers to an individual having two identical alleles for a particular gene. Karyotype, on the other hand, refers to the complete set of chromosomes in an individual.
Among all the molecules significant to biology, which of the following are considered the most important?
- A. Carbohydrates, lipids, protein, and nucleic acids
- B. Carbohydrates, lipids, protein, and calcium
- C. Carbohydrates, lipids, protein, and sulfur
- D. Carbohydrates, lipids, protein, and iron
Correct Answer: A
Rationale: The correct answer is A: Carbohydrates, lipids, protein, and nucleic acids. These four types of molecules are crucial to biological systems. Carbohydrates provide energy and structural support, lipids serve as energy storage and cell membrane components, proteins have diverse functions in cells, and nucleic acids carry genetic information. While the other choices may have biological importance, nucleic acids play a fundamental role in storing and transmitting genetic information, making them essential in the context of biology.
In the example provided in question 23, which type of solution is the egg placed in?
- A. Hypertonic
- B. Isotonic
- C. Hypotonic
- D. None of the above
Correct Answer: A
Rationale: When an egg is placed in a hypertonic solution, there is a higher concentration of solutes outside the egg compared to inside. This concentration gradient causes water to move out of the egg through osmosis, leading to the egg shrinking or shriveling due to the loss of water. Therefore, the correct answer is 'Hypertonic.'
What substances make up the bilayer of the cellular membrane?
- A. Nucleic acids
- B. Phospholipids
- C. Proteins
- D. Carbohydrates
Correct Answer: B
Rationale: The cellular membrane consists of a bilayer of phospholipids. This phospholipid bilayer forms a flexible barrier around the cell, providing structural integrity and fluidity. While proteins and carbohydrates are also present in the cell membrane, the main component of the membrane's structure is the phospholipid bilayer, which plays a crucial role in maintaining the cell's functions.