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.