Which organ of the body compensates when a person's intake of vitamins decreases?
- A. Appendix
- B. Liver
- C. Pancreas
- D. Stomach
Correct Answer: B
Rationale: The liver is the organ that compensates when a person's intake of vitamins decreases. It stores certain vitamins, such as vitamins A, D, E, K, and B12, and releases them when dietary intake decreases. This helps maintain the body's vitamin levels and functions. The other organs listed - Appendix, Pancreas, and Stomach - do not primarily play a role in compensating for a decrease in vitamin intake. The liver is crucial in maintaining vitamin balance, making it the correct choice in this context.
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What substance is required to drive the sliding filament process during muscle contraction?
- A. ATP
- B. Hormone
- C. Potassium
- D. Water
Correct Answer: A
Rationale: The substance required to drive the sliding filament process during muscle contraction is ATP (adenosine triphosphate). ATP provides the energy needed for muscle contraction by enabling the myosin heads to bind to actin and generate force. This energy release drives the sliding of the filaments, causing muscle fibers to contract. Hormones, potassium, and water do not directly drive the sliding filament process in muscle contraction. Hormones are signaling molecules that regulate various physiological processes but do not directly provide energy for muscle contraction. Potassium is an electrolyte important for nerve and muscle function but is not the primary driver of the sliding filament process. Water is essential for overall hydration and bodily functions but does not directly participate in the muscle contraction process.
What is a rod-shaped structure that forms when a single DNA molecule and its associated proteins coil tightly before cell division?
- A. Centromere
- B. Chromatid
- C. Chromosome
- D. Gene
Correct Answer: C
Rationale: A chromosome is a rod-shaped structure that forms when a single DNA molecule and its associated proteins coil tightly before cell division. It contains the genetic material and is essential for cell division and replication. The centromere is a specific region of a chromosome that plays a role in cell division. A chromatid is one half of a duplicated chromosome, and a gene is a unit of heredity responsible for specific traits. Therefore, the correct answer is 'Chromosome' as it represents the entire condensed DNA molecule during cell division.
After a person eats birthday cake, which of the following enzymes is needed to break down the sucrose in the cake?
- A. Lactase
- B. Maltase
- C. Peptidase
- D. Sucrase
Correct Answer: D
Rationale: Sucrase is the correct enzyme needed to break down sucrose into its component sugars, glucose, and fructose. Lactase is responsible for breaking down lactose, maltase for maltose, and peptidase for proteins; therefore, they are not the enzymes required to digest sucrose specifically. In the context of digesting birthday cake, which contains sucrose, sucrase is the enzyme needed for this particular sugar.
Which structure protects the lungs?
- A. Femur
- B. Ribcage
- C. Scapula
- D. Skull
Correct Answer: B
Rationale: The ribcage is the correct answer. It protects the lungs by providing structural support and shielding them from injury. The femur is a bone in the thigh and does not protect the lungs. The scapula is a shoulder blade bone, and the skull protects the brain, not the lungs.
At what stage is urine formed in the kidney?
- A. After fluid reaches the bladder.
- B. When fluid fills the collecting duct.
- C. Before blood enters the glomerulus.
- D. During fluid transport to the urethra.
Correct Answer: B
Rationale: Urine is formed when fluid fills the collecting duct in the kidney. The collecting duct is where the final concentration of urine occurs after the filtration process in the nephron. Choice A is incorrect because urine formation happens before fluid reaches the bladder. Choice C is incorrect because urine formation occurs after blood has been filtered in the glomerulus. Choice D is incorrect because urine formation happens before fluid is transported to the urethra for elimination.