Question
Conversion of glucose to glucose-6-phosphate, the first irreversible reaction of glycolysis, is catalysed by [NEET (National) 2019]
(a) hexokinase
(b) enolase
(c) phosphofructokinase
(d) aldolase
Answer/Explanation
Ans. (a)
Conversion of glucose to glucose-6-phosphate during glycolysis is catalysed by the enzyme hexokinase. During this step, glucose is phosphorylated to glucose-6-phosphate by ATP. It is the first step of activation phase of glycolysis.
Question
Which of the following biomolecules is common to respiration-mediated breakdown of fats, carbohydrates and proteins? [NEET 2016, Phase II]
(a) Glucose-6-phosphate
(b) Fructose 1,6-bisphosphate
(c) Pyruvic acid
(d) Acetyl Co-A
Answer/Explanation
Ans. (d)
Carbohydrates, fats and proteins, all can be used as a substrate in cellular respiration. All of them first get converted to acetyl Co-A to enter into Krebs’ cycle of aerobic cellular respiration. Thus, it is the common factor of respiration entering Krebs’ cycle after breakdown of carbohydrates, fats and proteins.
Question
In glycolysis, during oxidation electrons are removed by [CBSE AIPMT 2004]
(a) ATP
(b) glyceraldehyde-3-phosphate
(c) $\mathrm{NAD}^{+}$
(d) molecular oxygen
Answer/Explanation
Ans. (c)
When 3-phosphoglyceraldehyde is converted into 1,3 diphosphoglyceric acid, two electrons and two protons are released which are utilised to convert $\mathrm{NAD}^{+}$to $\mathrm{NADH}$ and one $\mathrm{H}^{+}$.
$
\mathrm{NAD}^{+}+2 \mathrm{H}^{+}+2 \mathrm{e}^{-} \rightarrow \mathrm{NADH}+\mathrm{H}^{+} \text {. }
$
Question
In animal cells, the first stage of glucose breakdown is [CBSE AIPMT 1994]
(a) Krebs’ cycle
(b) glycolysis
(c) oxidative phosphorylation
(d) ETC
Answer/Explanation
Ans. (b)
Glycolysis refers to the sequence of reactions by which glucose is degraded anaerobically into pyruvic acid inside cytoplasm. The net gain of molecules of ATP during glycolysis is 2.
Question
End product of glycolysis is [CBSE AIPMT 1990]
(a) acetyl Co-A
(b) pyruvic acid
(c) glucose 1-phosphate
(d) fructose 1-phosphate
Answer/Explanation
Ans. (b)
During glycolysis one molecule of glucose is broken down into two molecules of pyruvic acid in the cytoplasm. Glycolysis is the common path of aerobic and anaerobic respiration.
Question
EMP can produce a total of [CBSE AIPMT 1990]
(a) 6 ATP
(b) 8 ATP
(c) 24 ATP
(d) 38 ATP
Answer/Explanation
Ans. (b)
EMP(Embden-Meyerhof Paranas Pathway) refers to glycolysis, in which one molecule of glucose is broken down to two molecules of pyruvic acid. In this process there is a gain of 2NADH $(2 \times 3$ ATP) and 2 ATP, i.e. total 8 ATP.
Question
Incomplete oxidation of glucose into pyruvic acid with several intermediate steps is known as [CBSE AIPMT 1988]
(a) TCA-pathway
(b) glycolysis
(c) HMS-pathway
(d) Krebs’ cycle
Answer/Explanation
Ans. (b)
Glycolysis is the sequence of enzyme mediated reactions by which glucose is degraded anaerobically into pyruvic acid in cell cytoplasm. The net gain of molecules of ATP during glycolysis is two.