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1. Which of the following is an example of a positive feedback loop in the
human body?
a) The regulation of blood glucose levels by insulin and glucagon
b) The secretion of oxytocin during childbirth to stimulate uterine
contractions
c) The maintenance of body temperature by sweating and shivering
d) The inhibition of gastric acid secretion by gastrin
Answer: B. A positive feedback loop is a process in which the output of a
system enhances or amplifies the initial stimulus, leading to an increased
response. In contrast, a negative feedback loop is a process in which the
output of a system counteracts or reduces the initial stimulus, leading to a
decreased or stabilized response. An example of a positive feedback loop
is the secretion of oxytocin during childbirth, which stimulates uterine
contractions, which in turn stimulate more oxytocin secretion, until the
baby is delivered. An example of a negative feedback loop is the
regulation of blood glucose levels by insulin and glucagon, which lower
and raise blood glucose levels, respectively, to keep them within a normal
range.
Rationale: This question tests the student's understanding of the concept of
feedback loops and their examples in the human body.
2. What is the role of ATP synthase in cellular respiration?
a) It catalyzes the oxidation of glucose to pyruvate in glycolysis
b) It transfers electrons from NADH and FADH2 to the electron transport
chain
c) It synthesizes ATP from ADP and inorganic phosphate using the proton
gradient
d) It splits water into oxygen and hydrogen ions in the light reactions of
photosynthesis
Answer: C. ATP synthase is an enzyme that synthesizes ATP from ADP
and inorganic phosphate using the energy from the proton gradient across
the inner mitochondrial membrane. The proton gradient is generated by
the electron transport chain, which receives electrons from NADH and
FADH2, the products of glycolysis and the Krebs cycle. ATP synthase is
also found in chloroplasts, where it uses the proton gradient generated by
the light reactions of photosynthesis to produce ATP.
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