,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.
, Rationale: This question tests the student's knowledge of the role and
function of ATP synthase in cellular respiration.
3. Which of the following statements is true about DNA replication?
a) It occurs in the nucleus during the S phase of the cell cycle
b) It involves breaking the hydrogen bonds between complementary base
pairs
c) It produces two identical copies of DNA, each with one old and one
new strand
d) All of the above
Answer: D. All of the statements are true about DNA replication. DNA
replication is the process by which DNA is copied before cell division. It
occurs in the nucleus during the S phase of the cell cycle, when DNA
synthesis takes place. It involves breaking the hydrogen bonds between
complementary base pairs on the two strands of DNA, using an enzyme
called DNA helicase. This creates a replication fork, where new
nucleotides are added to each strand by an enzyme called DNA
polymerase, following the base pairing rules (A with T, and G with C).
This results in two identical copies of DNA, each with one old (parental)
and one new (daughter) strand. This mode of replication is called semi-
conservative.
Rationale: This question assesses the student's comprehension of the
process and characteristics of DNA replication.
1. Which of the following is TRUE about osmosis?
A. It is the movement of water from an area of low concentration to an
area of high concentration
B. It is the movement of water from an area of high concentration to an
area of low concentration
C. It is the movement of water from an area of low solute concentration to
an area of high solute concentration
D. It is the movement of water from an area of high solute concentration
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