Q-1. Gibbs changes in free energy (ΔG) is negative, process is
a) Exergonic
b) Endergonic
c) Proceeds spontaneously
d) System is at equilibrium
Answer: a and c
Explanation:
Negative Gibbs changes in free energy (-ΔG):
Reaction proceeds spontaneously
Exergonic reaction
Positive Gibbs changes in free energy (+ΔG):
Reaction proceeds only if free energy can be gained
Endergonic reaction
Important point:
If Gibbs changes in free energy (ΔG) is zero, the system is at equilibrium and no net change take place.
Q-2. Which of the following doesn’t contain high energy phosphate?
a) ATP
b) ADP
c) AMP
d) None
Answer: AMP
Explanation:
ATP contains two high energy phosphate groups and ADP contains one whereas the phosphate in AMP is of low energy type.
Q-3. One high energy phosphate is generated directly in the citric acid cycle at
a) Succinate thiokinase step
b) Aconitase step
c) Fumarase step
d) Succinate dehydrogenase step
Answer: Succinate thiokinase step
Explanation:
A net formation of two high energy phosphate results from the formation of lactate from one molecules of glucose, generated in two reactions catalysed by phosphoglycerate kinase and pyruvate kinase.
Important point:
One high energy phosphate is generated directly in the citric acid cycle at Succinate thiokinase step.
Q-4. Not true about Phosphagens
a) Storage forms of high energy phosphate
b) Include creatine phosphate and arginine phosphate
c) High ATP/ADP favors store of high energy phosphate
d) Low ATP/ADP favors store of high energy phosphate
Answer: Low ATP/ADP favors store of high energy phosphate
Explanation:
Phosphagens:
Storage forms of high energy phosphate
Include creatine phosphate in vertebrate and arginine phosphate in invertebrate
High ATP/ADP favors store of high energy phosphate
Q-5. Not true about first step of glycolysis
a) Endergonic
b) Exergonic
c) Cannot proceed under physiological condition
d) Requires Mg++
Answer: Exergonic
Explanation:
First step of glycolysis:
Highly Endergonic and cannot proceed under physiological condition
Requires Mg++
Catalysed by hexokinase or glucokinase
Q-6. Glowing of firefly is due to? (AIIMS Nov 2008)
a) ATP
b) NADH
c) GTP
d) Phospho-creatinine
Answer: ATP
Explanation:
The method by which fireflies produce light is perhaps the best known example of bioluminescence.
When oxygen combines with calcium, adenosine tri-phosphate (ATP) and the chemical luciferin in the presence of luciferase, a bioluminescent enzyme, light is produced.
Q-7. Which statement is incorrect? (AIIMS Nov 2009)
a) Chemiluminescene: excited electron in higher orbit comes to lower orbit by emitting energy in form of photon
b) Bioluminescence: is a form of chemiluminescence
c) Phosphorescence: is energy emitted following absorption of EM radiation
d) Electro-chemiluminescence: is energy emitted by photon
Answer: Electro-chemiluminescence: is energy emitted by photon
Explanation:
Luminescence is “cold light” that can be emitted at normal and lower temperatures. In luminescence, some energy source kicks an electron of an atom out of its lowest energy “ground” state into a higher energy “excited” state; then the electron returns the energy in the form of light so it can fall back to its “ground” state.
Several varieties of luminescence:
Chemiluminescence is luminescence where the energy is supplied by chemical reactions.
Bioluminescence is luminescence caused by chemical reactions in living things; it is a form of chemiluminescence. Fireflies glow by bioluminescence.
Phosphorescence is delayed luminescence or “afterglow”.
In fluorescence, an electron is raised from the ground level to an excited level by a light photon or other radiation. It may get trapped there for some time.
Electro-chemiluminescence or electro-generated chemiluminescence (ECL) is a kind of luminescence produced during electrochemical reactions in solutions.