Glycolysis Questions in English

(D) In glycolysis,the enzyme enolase catalyzes the conversion of $2$-phosphoglycerate to phosphoenolpyruvate $(PEP)$.
During this reaction,a molecule of water $(H_2O)$ is removed from the substrate,which is known as a dehydration reaction.
Option $A$ involves phosphorylation,option $B$ involves oxidation and phosphorylation,and option $C$ involves the removal of a phosphate group.

(B) Glycolysis is the initial and fundamental pathway of cellular respiration. It is common to both aerobic and anaerobic respiration and occurs in the cytosol of all living cells,including both prokaryotes and eukaryotes.

(D) In cellular respiration,whether aerobic or anaerobic,$Glucose$ is the primary substrate that undergoes oxidation to produce energy in the form of $ATP$.
In plants,$Glucose$ is derived from $Sucrose$,which is the end product of photosynthesis or from stored carbohydrates.
$Sucrose$ is converted into $Glucose$ and $Fructose$ by the enzyme $Invertase$ to enter the first step of respiration,known as the $Glycolytic$ pathway.
Because $Glucose$ is a simple sugar that enters the respiratory pathway directly,it serves as the most immediate or instantaneous source of energy for the cell.

(A) Glycolysis is the process where one molecule of $6$-carbon glucose is broken down into two molecules of $3$-carbon pyruvic acid.
This process occurs in the cytosol of the cell.
During glycolysis,$2$ molecules of $ATP$ are produced (net gain),and $2$ molecules of $NAD^+$ are reduced to $NADH$ for every glucose molecule.
Since $NADH$ produced in glycolysis enters the electron transport chain $(ETC)$ to produce $ATP$,it has a direct connection with the $ETC$.
Therefore,only statement $I$ is correct.

(C) Glycolysis is the process of the breakdown of a glucose molecule into two molecules of pyruvic acid.
It results in a net gain of $2$ $ATP$ molecules per glucose molecule.
Glycolysis occurs in the cytoplasm of the cell and is common to both aerobic and anaerobic respiration,as it does not require oxygen.

(D) Glycolysis is a metabolic pathway consisting of $10$ distinct enzymatic steps. Each step in this pathway is catalyzed by a specific enzyme to facilitate the conversion of substrates into products,ensuring the process proceeds efficiently toward the formation of pyruvic acid.

(A) In glycolysis,$ATP$ is synthesised via substrate-level phosphorylation at two specific steps:
$(i)$ Conversion of $1,3$-bisphosphoglycerate to $3$-phosphoglycerate,catalyzed by phosphoglycerate kinase.
$(ii)$ Conversion of phosphoenolpyruvate $(PEP)$ to pyruvate,catalyzed by pyruvate kinase.
Among the given options,the conversion of $1,3$-bisphosphoglycerate to $3$-phosphoglycerate is a step where $ATP$ is produced.

(C) $I$. Glycolysis is the partial oxidation of one molecule of glucose into two molecules of pyruvic acid. It results in a net gain of $2$ $ATP$ molecules.
$II$. Glycolysis occurs in the cytoplasm of all living cells,whether prokaryotic or eukaryotic.
$III$. During the preparatory phase of glycolysis,$2$ $ATP$ molecules are consumed: one during the phosphorylation of glucose to glucose-$6$-phosphate and another during the phosphorylation of fructose-$6$-phosphate to fructose-$1,6$-bisphosphate.
$IV$. The metabolic pathway of glycolysis is also known as the $EMP$ pathway,named after its discoverers: Gustav Embden,Otto Meyerhof,and $J$. Parnas.
Since all four statements are correct,the correct option is $C$.

(B) Mitochondria are known as the powerhouse of the cell.
$1$. Glyceraldehyde-$3$-phosphate dehydrogenation is a key step in glycolysis,which occurs in the cytoplasm,not in the mitochondria.
$2$. Glycine decarboxylation occurs in the mitochondria during photorespiration.
$3$. Fumaric acid hydration is a step in the Krebs cycle ($TCA$ cycle),which occurs in the mitochondrial matrix.
$4$. Cytochrome oxidation is a part of the Electron Transport System $(ETS)$,which occurs on the inner mitochondrial membrane.

(B) In the glycolytic pathway, Glyceraldehyde $3$-phosphate ($3$-$PGAL$) is converted into $1,3$-bisphosphoglycerate ($1,3$-$BPG$) by the enzyme glyceraldehyde $3$-phosphate dehydrogenase.
This reaction involves the oxidation of $3$-$PGAL$ and the addition of an inorganic phosphate group $(P_i)$.
During this process, $NAD^+$ is reduced to $NADH + H^+$.
The reaction is: $3$-phosphoglyceraldehyde $+ NAD^+ + P_i \rightarrow 1,3$-bisphosphoglycerate $+ NADH + H^+$.

(A) The common step for both aerobic and anaerobic respiration is Glycolysis,also known as the $EMP$ pathway (Embden-Meyerhof-Parnas pathway).
In this process,one molecule of glucose is broken down into two molecules of pyruvic acid in the cytoplasm.
After glycolysis,the fate of pyruvic acid depends on the availability of oxygen,leading either to aerobic respiration (Krebs cycle) or anaerobic respiration (fermentation).

(A) The pathway described by Embden,Meyerhof,and Parnas is known as the $EMP$ pathway,which is another name for Glycolysis. This metabolic process occurs in the cytoplasm and involves the breakdown of one molecule of glucose into two molecules of pyruvic acid.

(A) Glycolysis is the first stage of cellular respiration. It takes place in the cytoplasm of all living cells,regardless of whether they are prokaryotic or eukaryotic,as it does not require oxygen.

(B) Glycolysis is the partial oxidation of one molecule of glucose $(6C)$ into two molecules of pyruvic acid $(3C)$.
Option $A$ is true because glycolysis does not require oxygen.
Option $B$ is false because one molecule of glucose produces two molecules of pyruvic acid,not one.
Option $C$ is true because glycolysis takes place in the cytoplasm of the cell.
Option $D$ is true because other hexose sugars like fructose can also enter the glycolytic pathway after being phosphorylated.

(B) In the $EMP$ pathway (Glycolysis),the enzyme $Aldolase$ catalyzes the cleavage of the $6$-carbon sugar $Fructose-1,6-bisphosphate$ into two $3$-carbon molecules: $Dihydroxyacetone$ $phosphate$ $(DHAP)$ and $Glyceraldehyde-3-phosphate$ $(G3P)$.
Glucose $\longrightarrow$ $Glucose-6-phosphate$ $\longrightarrow$ $Fructose-6-phosphate$ $\longrightarrow$ $Fructose-1,6-bisphosphate$ $\xrightarrow{\text{Aldolase}}$ $2$ molecules of $Triose$ $phosphate$.

(A) During glycolysis,the fructose-$1,6$-bisphosphate is cleaved into two $3$-carbon compounds: glyceraldehyde-$3$-phosphate ($G$-$3$-$P$) and dihydroxyacetone phosphate $(DHAP)$.
These two triose phosphates are isomers of each other.
The enzyme that catalyses the reversible interconversion between glyceraldehyde-$3$-phosphate and dihydroxyacetone phosphate is known as triose phosphate isomerase (also referred to as phosphotriose isomerase).
Therefore,the correct option is $A$.

(B) In the process of glycolysis,the oxidation of Glyceraldehyde-$3$-phosphate $(G3P)$ to $1,3$-bisphosphoglyceric acid $(1,3-BPGA)$ is catalyzed by the enzyme Glyceraldehyde-$3$-phosphate dehydrogenase.
During this reaction,$NAD^+$ is reduced to $NADH + H^+$,which serves as a crucial reducing power for subsequent metabolic processes.

(C) Phosphofructokinase $(PFK)$ is known as the pacemaker enzyme of glycolysis.
It catalyzes the irreversible conversion of fructose-$6$-phosphate to fructose-$1,6$-bisphosphate.
This step is the rate-limiting step of the glycolytic pathway,which determines the overall flux of the process based on the cell's energy requirements.

(B) In the process of glycolysis,the conversion of glucose to glyceraldehyde-$3$-phosphate occurs in the preparatory phase.
$1$. First,glucose is phosphorylated to glucose-$6$-phosphate by the enzyme hexokinase,which consumes $1$ $ATP$ molecule.
$2$. Then,glucose-$6$-phosphate is isomerized to fructose-$6$-phosphate.
$3$. Finally,fructose-$6$-phosphate is phosphorylated to fructose-$1,6$-bisphosphate by the enzyme phosphofructokinase,which consumes another $1$ $ATP$ molecule.
$4$. Fructose-$1,6$-bisphosphate is then split into glyceraldehyde-$3$-phosphate and dihydroxyacetone phosphate.
Thus,a total of $2$ $ATP$ molecules are consumed in this phase.

(A) Glycolysis begins with the phosphorylation of glucose to form glucose-$6$-phosphate. This reaction is catalyzed by the enzyme $Hexokinase$ in the presence of $ATP$ and $Mg^{2+}$.
Equation: $\text{Glucose} \xrightarrow{\text{Hexokinase}} \text{Glucose-}6\text{-Phosphate}$.

(C) In the process of glycolysis,the conversion of fructose-$6$-phosphate to fructose-$1,6$-bisphosphate is an irreversible step.
This reaction is catalyzed by the enzyme Phosphofructokinase $(PFK)$.
This step consumes one molecule of $ATP$ and is a key regulatory point in the glycolytic pathway.
The reaction is represented as: Fructose-$6$-phosphate + $ATP$ $\xrightarrow{\text{Phosphofructokinase}}$ Fructose-$1,6$-bisphosphate + $ADP$.

(B) In the process of glycolysis,$3$-$PGAL$ (glyceraldehyde $3$-phosphate) is oxidized to $1,3$-bisphosphoglycerate. During this reaction,$2$ redox equivalents (in the form of $2H^+$ and $2e^-$) are removed from each molecule of $3$-$PGAL$ to reduce $NAD^+$ to $NADH + H^+$. Therefore,for two molecules of $3$-$PGAL$,a total of $4$ redox equivalents are removed.

(B) Substrate level phosphorylation is the direct transfer of a phosphate group from a substrate molecule to $ADP$ to form $ATP$.
In the reaction $1,3-bisphosphoglycerate \longrightarrow 3-phosphoglycerate$,$ATP$ is produced.
In the reaction $Phosphoenolpyruvate \longrightarrow Pyruvate$,$ATP$ is produced.
In the reaction $Succinyl-CoA \longrightarrow Succinic acid$,$GTP$ (or $ATP$) is produced.
In the reaction $3-phosphoglycerate \longrightarrow 2-phosphoglycerate$,there is no phosphate transfer to $ADP$; instead,the phosphate group is simply shifted from the $3^{rd}$ carbon to the $2^{nd}$ carbon by the enzyme phosphoglyceromutase.

(A) During glycolysis,$PGAL$ (glyceraldehyde-$3$-phosphate) is oxidized to $BPGA$ ($1,3$-bisphosphoglyceric acid).
In this step,two redox-equivalents are removed from $PGAL$ in the form of hydrogen atoms and transferred to a molecule of $NAD^{+}$ to form $NADH + H^{+}$.
$PGAL$ also reacts with inorganic phosphate $(Pi)$ to form $BPGA$.
Subsequently,$BPGA$ is converted into $3$-phosphoglyceric acid $(PGA)$ by the enzyme phosphoglycerate kinase,a process that yields $ATP$ from $ADP$.

(B) Glycolysis is a common pathway for both aerobic and anaerobic respiration,where glucose is broken down into two molecules of pyruvic acid.
In skeletal muscle cells,under aerobic conditions,the end product of glycolysis is pyruvic acid,which then enters the Krebs cycle.
In yeast,during anaerobic fermentation,the pyruvic acid produced by glycolysis is further converted into ethanol and $CO_{2}$.
Therefore,the products are pyruvic acid and ethanol + $CO_{2}$ respectively.

(B) The process of converting one molecule of glucose into two molecules of pyruvic acid is known as glycolysis.
During glycolysis,$2$ molecules of $ATP$ are consumed in the preparatory phase.
In the payoff phase,$4$ molecules of $ATP$ are produced via substrate-level phosphorylation.
Therefore,the net gain of $ATP$ is $4 - 2 = 2$ molecules of $ATP$ per molecule of glucose.

(B) Glycolysis is a catabolic process because it involves the breakdown of glucose into two molecules of pyruvic acid.
It is a series of $10$ enzyme-catalyzed reactions that occur in the cytoplasm of the cell.

(C) Glycolysis is a metabolic pathway that converts glucose $(C_6H_{12}O_6)$ into pyruvate $(CH_3COCOO^-)$.
This process consists of a series of $10$ enzyme-catalyzed reactions.
Each step in the glycolytic pathway is mediated by a specific enzyme,such as hexokinase,phosphofructokinase,and pyruvate kinase,among others.
Therefore,a total of $10$ different enzymes are required to complete the process of glycolysis.

(D) Glycolysis is the process of breakdown of glucose into two molecules of pyruvic acid.
It is known as the $EMP$ pathway,named after its discoverers Embden,Meyerhof,and Parnas.
It is the first stage of respiration that occurs in the cytoplasm of the cell.
Since it does not require oxygen,it is considered the anaerobic phase of respiration,even in aerobic organisms.
Therefore,all the given statements are correct.

(A) In the process of glycolysis,the conversion of Glucose-$6$-phosphate to Fructose-$6$-phosphate is catalyzed by the enzyme phosphoglucose isomerase.
Option $A$ states 'Glucose-$6$-phosphate $\rightarrow$ Phosphate-$6$-phosphate',which is chemically incorrect and does not represent a standard step in glycolysis.
Option $B$ $(PGAL \rightarrow DHAP)$ is a reversible reaction catalyzed by triose phosphate isomerase.
Option $C$ $(3-PGA \rightarrow 2-PGA)$ is catalyzed by phosphoglyceromutase.
Option $D$ ($PEP \rightarrow$ Pyruvic acid) is the final step of glycolysis catalyzed by pyruvate kinase.
Therefore,option $A$ is the incorrect reaction.

(B) The conversion of glucose into glucose-$6$-phosphate is the first step of glycolysis.
This reaction is catalyzed by the enzyme hexokinase.
In this process,one molecule of $ATP$ is consumed to provide the phosphate group,and the reaction is irreversible under physiological conditions.

(C) Glycolysis is a metabolic pathway that converts glucose $(C_6H_{12}O_6)$ into pyruvate $(CH_3COCOO^-)$.
During this process,$NAD^+$ is reduced to $NADH + H^+$,while glucose is oxidized to pyruvate.
Since both oxidation and reduction reactions occur simultaneously in this pathway,it is classified as a redox process.

(A) In the process of glycolysis,the conversion of $2$-phosphoglycerate $(2-PGA)$ to phosphoenolpyruvate $(PEP)$ is catalyzed by the enzyme enolase.
This reaction involves the removal of a water molecule $(H_2O)$,which is known as a dehydration reaction.
Therefore,the correct process completed by dehydration is $2$-phosphoglycerate $\rightarrow$ phosphoenolpyruvate.

(C) Glycolysis is the first stage of cellular respiration. It involves the breakdown of glucose into two molecules of pyruvate. This process occurs in the cytoplasm of the cell,as the enzymes required for the ten steps of glycolysis are present in the cytosol.

(A) The correct matching is based on the carbon skeleton and phosphate groups present in the intermediates of glycolysis:
$P$. Fructose $1, 6$-bisphosphate: It is a $6$-carbon sugar with $2$ phosphate groups. Hence, $(P-III)$.
$Q$. Glucose-$6$-phosphate: It is a $6$-carbon sugar with $1$ phosphate group. Hence, $(Q-IV)$.
$R$. $DHAP$ (Dihydroxyacetone phosphate): It is a $3$-carbon triose sugar with $1$ phosphate group. Hence, $(R-II)$.
$S$. $BPGA$ ($1, 3$-bisphosphoglyceric acid): It is a $3$-carbon molecule with $2$ phosphate groups. Hence, $(S-I)$.
Therefore, the correct sequence is $(P-III), (Q-IV), (R-II), (S-I)$.

(D) Glycolysis is the partial oxidation of glucose into two molecules of pyruvic acid.
$1$. The term 'Glycolysis' has originated from the Greek words 'glycos' (sugar) and 'lysis' (splitting),meaning the splitting of sugar.
$2$. This metabolic pathway was discovered by Gustav Embden,Otto Meyerhof,and $J$. Parnas,and is often referred to as the $EMP$ pathway.
$3$. Glycolysis is the only process of respiration in anaerobic organisms and is the first step of respiration in aerobic organisms. Thus,it occurs in all living organisms.

(C) Glycolysis,also known as the $EMP$ pathway,is the process of breaking down one molecule of glucose into two molecules of pyruvic acid.
This metabolic pathway consists of a series of $10$ enzyme-catalyzed reactions.
These reactions occur in the cytoplasm of the cell and do not require oxygen.
Therefore,the correct number of steps in glycolysis is $10$.

(D) During glycolysis,$4$ molecules of $ATP$ are produced through substrate-level phosphorylation (two in the conversion of $1,3$-bisphosphoglycerate to $3$-phosphoglycerate and two in the conversion of phosphoenolpyruvate to pyruvate).
$2$ molecules of $ATP$ are consumed during the preparatory phase (one in the phosphorylation of glucose to glucose-$6$-phosphate and one in the phosphorylation of fructose-$6$-phosphate to fructose-$1,6$-bisphosphate).
Therefore,the number of $ATP$ produced is $4$ and consumed is $2$.

(B) Glycolysis is the breakdown of glucose into two molecules of pyruvic acid.
During the conversion of glyceraldehyde$-3-$phosphate $(G3P)$ to $1,3-$bisphosphoglycerate,the enzyme glyceraldehyde$-3-$phosphate dehydrogenase catalyzes the reduction of $NAD^+$ to $NADH + H^+$.
Since one molecule of glucose produces two molecules of $G3P$,this step occurs twice per glucose molecule.
Therefore,a total of $2$ $NADH + H^+$ molecules are produced during glycolysis.

(A) Glycolysis is the common pathway for both aerobic and anaerobic respiration (including lactic acid and alcoholic fermentation).
In glycolysis,$1$ molecule of glucose $(6C)$ is broken down into $2$ molecules of pyruvic acid $(3C)$.
This process occurs in the cytoplasm of the cell and does not require oxygen.
Since all three processes (lactic acid fermentation,alcoholic fermentation,and aerobic respiration) start with the breakdown of glucose into pyruvic acid,glycolysis is the common stage.

(C) In the process of glycolysis:
$1$. The conversion of Glucose to Glucose$-6-$phosphate is catalyzed by the enzyme Hexokinase $(P)$.
$2$. The conversion of Phosphoenolpyruvate to Pyruvic acid is catalyzed by the enzyme Pyruvate kinase $(Q)$.
$3$. Among the given options,the enzyme Enolase is involved in the step preceding the formation of Phosphoenolpyruvate (conversion of $2-$phosphoglycerate to phosphoenolpyruvate). However,looking at the options provided,the most appropriate choice for $P$ is Hexokinase. Since Pyruvate kinase is not listed,we evaluate the options based on the provided choices. Option $C$ lists Hexokinase for $P$ and Enolase for $Q$,which is the closest match in the context of glycolytic enzymes provided in the options.

(C) In glycolysis,$ATP$ is produced during the conversion of $1, 3$-bisphosphoglyceric acid $(1, 3-BPGA)$ to $3$-phosphoglyceric acid $(3-PGA)$ and during the conversion of phosphoenolpyruvate $(PEP)$ to pyruvic acid. These steps are examples of substrate-level phosphorylation. However,the conversion of Fructose-$6$-phosphate to Fructose-$1, 6$-bisphosphate is an energy-consuming step where $ATP$ is utilized (hydrolyzed to $ADP$),not produced. Therefore,$ATP$ is not produced in option $C$.

(A) During the process of glycolysis,$1$ molecule of glucose ($6$ carbons) is broken down into $2$ molecules of pyruvic acid ($3$ carbons each).
In the energy-payoff phase,$4$ $ATP$ molecules are produced through substrate-level phosphorylation.
However,$2$ $ATP$ molecules are consumed during the preparatory phase (investment phase) to phosphorylate glucose and fructose$-6-$phosphate.
Therefore,the net gain of $ATP$ molecules in glycolysis is $4 - 2 = 2$ $ATP$.

(A) During the process of glycolysis,one molecule of glucose $(C_6H_{12}O_6)$ is broken down into two molecules of pyruvic acid.
In this pathway,a total of $4$ $ATP$ molecules are produced through substrate-level phosphorylation.
However,$2$ $ATP$ molecules are consumed during the preparatory phase (phosphorylation of glucose and fructose$-6-$phosphate).
Therefore,the net gain of $ATP$ molecules in glycolysis is $4 - 2 = 2$ $ATP$ per glucose molecule.

(B) $ATP$ is consumed in glycolysis at two specific phosphorylation steps:
$1$. Conversion of Glucose to Glucose-$6$-phosphate (catalyzed by hexokinase).
$2$. Conversion of Fructose-$6$-phosphate to Fructose-$1,6$-bisphosphate (catalyzed by phosphofructokinase).
Since both statements correctly describe the process of phosphorylation in glycolysis,Assertion $A$ is true,and Reason $R$ provides the correct explanation for why $ATP$ is used.

(C) In the process of glycolysis,the oxidation of $3$-phosphoglyceraldehyde (also known as glyceraldehyde-$3$-phosphate) to $1,3$-bisphosphoglycerate is a crucial step.
During this reaction,the enzyme glyceraldehyde-$3$-phosphate dehydrogenase catalyzes the oxidation of the aldehyde group to a carboxylic acid group.
Simultaneously,$NAD^{+}$ is reduced to $NADH + H^{+}$ by accepting electrons and protons released during the oxidation process.
This is the only step in the glycolytic pathway where $NADH$ is produced.

(D) Glycolysis is the partial oxidation of glucose into two molecules of pyruvic acid.
It involves the breakdown of $\text{C}-\text{C}$ bonds during the conversion of fructose$-1,6-$bisphosphate into $\text{DHAP}$ and $\text{PGAL}$.
Oxidation occurs during the conversion of $\text{PGAL}$ to $1,3$-bisphosphoglyceric acid,where $\text{NAD}^+$ is reduced to $\text{NADH} + \text{H}^+$.
Dehydration occurs during the conversion of $2$-phosphoglycerate to phosphoenolpyruvate $(PEP)$ by the enzyme enolase.
However,$\text{PGAL}$ (Phosphoglyceraldehyde) is an intermediate product of glycolysis,not the final product. The final product of the glycolytic pathway is pyruvic acid.

(D) Glycolysis is the breakdown of glucose into two molecules of pyruvic acid.
$1$. It is an oxygen-independent pathway,meaning it can occur in both aerobic and anaerobic conditions.
$2$. In the pathway,one molecule of glucose $(6C)$ is converted into two molecules of $3-PGAL$ $(3C)$,which eventually produces two molecules of pyruvic acid $(3C)$.
$3$. It occurs in the cytoplasm of the cell.
$4$. The statement 'This process is completed with both glucose and fructose' is incorrect because glycolysis specifically refers to the degradation of glucose. While fructose can enter the glycolytic pathway after being converted into fructose-$6$-phosphate,the process itself is defined as the breakdown of glucose.

(D) Glycolysis is the process of the partial oxidation of glucose into two molecules of pyruvic acid.
In this process,one molecule of glucose $(C_6H_{12}O_6)$ is broken down into two molecules of pyruvate $(CH_3COCOOH)$ through a series of ten enzyme-catalyzed reactions.
Therefore,the end product of glycolysis is pyruvate.

(D) Glycolysis is the process of the breakdown of glucose into two molecules of pyruvic acid.
This process occurs in the cytoplasm of the cell and does not require oxygen.
During the entire pathway of glycolysis,there is no decarboxylation step.
Therefore,no $CO_2$ molecules are released during glycolysis.
The release of $CO_2$ occurs during the link reaction (pyruvate oxidation) and the Krebs cycle ($TCA$ cycle) in the mitochondria.