Glycolysis Questions in English

(A) In glycolysis,hexokinase catalyzes the phosphorylation of glucose to glucose-$6$-phosphate.
Glucose-$6$-phosphate acts as an allosteric inhibitor of the enzyme hexokinase.
This is a classic example of feedback inhibition (or end-product inhibition),where the product of a metabolic pathway inhibits an enzyme that acts early in the pathway to regulate the flux of the reaction and prevent the over-accumulation of the product.

(B) Glycolysis is the common metabolic pathway for both aerobic and anaerobic respiration.
In this process,one molecule of glucose is broken down into two molecules of pyruvic acid.
Therefore,pyruvic acid is the common intermediate product formed in both types of respiration.

(D) In cellular respiration,carbohydrates are the primary substrates used for energy production.
Among carbohydrates,sucrose is the most common form of sugar transported in plants,which is then broken down into hexose sugars like glucose and fructose to enter the glycolytic pathway.
Therefore,hexose sugars are the immediate substrates utilized first in the process of respiration.

(D) Glycolysis is also known as the $EMP$ pathway. It was discovered by Gustav Embden,Otto Meyerhof,and Jakub Karol Parnas in $1930$. Since these names are not listed in the options,the correct answer is $D$.

(B) The enzyme enolase catalyzes the conversion of $2-phosphoglycerate$ $(2-PGA)$ into $phosphoenolpyruvate$ $(PEP)$ during the process of glycolysis.
In this reaction, $2-PGA$ acts as the substrate, and a water molecule is removed in the presence of $Mg^{2+}$ ions.

(A) The conversion of fructose-$6$-phosphate to fructose-$1,6$-bisphosphate is an irreversible step in glycolysis.
This reaction is catalysed by the enzyme phosphofructokinase in the presence of $Mg^{2+}$ ions.
The reaction is as follows:
Fructose-$6$-phosphate + $ATP$ $\xrightarrow{\text{Phosphofructokinase, } Mg^{2+}}$ Fructose-$1,6$-bisphosphate + $ADP$.

(B) During the process of glycolysis,two molecules of $ATP$ are consumed in the preparatory phase.
First,$ATP$ is used to phosphorylate glucose into glucose-$6$-phosphate.
Second,$ATP$ is used to phosphorylate fructose-$6$-phosphate into fructose-$1, 6$-bisphosphate.
Therefore,a total of $2$ $ATP$ molecules are required for the initial phosphorylation steps of a single glucose molecule.

(B) Neuberg's ester is the historical name given to Fructose-$6$-phosphate.
It was named after the biochemist Carl Neuberg,who made significant contributions to the study of fermentation and glycolysis.
Therefore,the correct option is $B$.

(C) The Harden and Young's ester is the historical name given to Fructose-$1,6$-bisphosphate (also known as Fructose-$1,6$-diphosphate).
It was discovered by Arthur Harden and William John Young in $1905$ during their studies on the fermentation of glucose by yeast extracts.
This compound is a key intermediate in the process of glycolysis,where it is formed by the phosphorylation of Fructose-$6$-phosphate by the enzyme phosphofructokinase.

(B) The enzyme pyruvate kinase catalyzes the final step of glycolysis.
In this reaction, phosphoenolpyruvate $(PEP)$ is converted into pyruvic acid (pyruvate) with the simultaneous production of $ATP$ from $ADP$.
The reaction is represented as: $\text{Phosphoenolpyruvate} + ADP \xrightarrow{Pyruvate \text{ } kinase, Mg^{2+}, K^+} \text{Pyruvate} + ATP$.

(A) In the process of $Glycolysis$, the conversion of $Glucose-6-phosphate$ into $Fructose-6-phosphate$ is an isomerization reaction.
This step is catalyzed by the enzyme $Phosphoglucose \text{ } isomerase$.
Since this reaction occurs during the initial phase of $Glycolysis$, the correct answer is $Glycolysis$.

(B) In the process of glycolysis,$4$ molecules of ${H_2}O$ are produced during the conversion of $2$-phosphoglycerate to phosphoenolpyruvate ($2$ molecules) and during other steps.
However,$2$ molecules of ${H_2}O$ are consumed during the phosphorylation steps or associated reactions.
Therefore,the net consumption of water molecules in glycolysis is $2$.

(C) In the process of glycolysis,the enzyme aldolase catalyzes the reversible cleavage of the $6$-carbon sugar fructose-$1,6$-bisphosphate into two $3$-carbon isomers: glyceraldehyde-$3$-phosphate (phosphoglyceraldehyde) and dihydroxyacetone phosphate.
This reaction is a type of lyase reaction where a carbon-carbon bond is broken without the use of water or oxidation-reduction.
Therefore,the primary function of aldolase is the cleavage of the substrate.

(A) When organic acids (like malic acid or citric acid) are used as respiratory substrates,they enter the respiratory pathway directly as intermediates of the $Kreb's$ cycle.
Since these substrates are already in the form of organic acids,the process of $Glycolysis$ (which is the breakdown of glucose into pyruvic acid) is bypassed.
Therefore,$Glycolysis$ does not operate in this specific metabolic condition.

(C) The first stage of cellular respiration is glycolysis,which occurs in the cytoplasm of the cell. During this process,one molecule of glucose $(C_6H_{12}O_6)$ is broken down into two molecules of pyruvic acid $(CH_3COCOOH)$. This process does not require oxygen and is common to both aerobic and anaerobic respiration.

(A) In the process of glycolysis,one molecule of glucose $(C_6H_{12}O_6)$ is broken down into two molecules of pyruvic acid $(CH_3COCOOH)$.
During the conversion of glyceraldehyde$-3-$phosphate to $1,3-$bisphosphoglycerate,the enzyme glyceraldehyde$-3-$phosphate dehydrogenase reduces $NAD^+$ to $NADH + H^+$.
Since two molecules of glyceraldehyde$-3-$phosphate are produced per glucose molecule,two molecules of $NADH + H^+$ are formed alongside the net gain of $2 \ ATP$ molecules.

(B) In the process of glycolysis,phosphorylation occurs when a phosphate group is added to a molecule.
Specifically,the conversion of Fructose $6$-phosphate to Fructose $1, 6$-bisphosphate is a key phosphorylation step catalyzed by the enzyme phosphofructokinase.
This reaction consumes $ATP$ to add a phosphate group to the molecule,making Fructose $1, 6$-bisphosphate a direct product of phosphorylation.

(D) Glycolysis is the first step of cellular respiration,which occurs in the cytoplasm of the cell.
During this process,one molecule of glucose $(C_6H_{12}O_6)$ is partially oxidized through a series of ten enzyme-catalyzed reactions.
The net result of glycolysis is the conversion of one molecule of glucose into two molecules of pyruvic acid $(CH_3COCOOH)$.
Therefore,the correct option is $D$.

(B) The $EMP$ pathway (Glycolysis) involves the breakdown of one molecule of glucose into two molecules of pyruvate.
During this process,$4$ $ATP$ molecules are produced by substrate-level phosphorylation,and $2$ $ATP$ molecules are consumed in the preparatory phase.
Additionally,$2$ $NADH + H^+$ molecules are produced.
In aerobic respiration,each $NADH$ molecule yields $3$ $ATP$ molecules via the electron transport system ($2 \times 3 = 6$ $ATP$).
Therefore,the total energy yield is $2$ (net $ATP$ from glycolysis) $+ 6$ ($ATP$ from $NADH$) $= 8$ $ATP$ molecules.

(B) Glycolysis is the first stage of cellular respiration.
It occurs in the cytoplasm of the cell.
It is an anaerobic process,meaning it does not require oxygen to proceed.
During glycolysis,one molecule of glucose is broken down into two molecules of pyruvic acid.

(B) Glycolysis is the process of the partial oxidation of glucose into two molecules of pyruvic acid.
In this pathway,one molecule of $6$-carbon glucose is broken down into two molecules of $3$-carbon pyruvic acid.
The overall reaction is: $C_6H_{12}O_6 + 2NAD^+ + 2ADP + 2Pi \to 2C_3H_4O_3 + 2NADH + 2H^+ + 2ATP$.

(A) Glycolysis is also known as the $EMP$ pathway.
It is named after the three scientists who discovered it: Gustav Embden,Otto Meyerhof,and Jakub Karol Parnas.
This metabolic pathway occurs in the cytoplasm of the cell and involves the breakdown of glucose into two molecules of pyruvate.

(C) In the first step of glycolysis,glucose is phosphorylated to glucose-$6$-phosphate by the enzyme hexokinase in the presence of $ATP$ and $Mg^{2+}$ ions.
This reaction is irreversible and consumes one molecule of $ATP$.

(A) Glycolysis is the process of the breakdown of glucose into pyruvic acid.
In this process,one molecule of glucose $(C_6H_{12}O_6)$ is converted into two molecules of pyruvic acid $(CH_3COCOOH)$.
This process occurs in the cytoplasm of the cell and does not require oxygen.

(C) Glycolysis is the common pathway for both aerobic and anaerobic respiration.
It occurs in the cytoplasm of the cell and does not require oxygen.
This process is also known as the $EMP$ pathway,named after its discoverers: Embden,Meyerhoff,and Parnas.

(A) Glycolysis is the partial oxidation of glucose into two molecules of pyruvic acid.
The overall balanced equation for glycolysis is: $C_6H_{12}O_6 + 2NAD^+ + 2ADP + 2Pi \rightarrow 2C_3H_4O_3 + 2NADH + 2H^+ + 2ATP$.
Here, $C_6H_{12}O_6$ represents glucose, and $C_3H_4O_3$ represents pyruvic acid.
Option $A$ represents the simplified conversion of glucose to pyruvic acid.

(A) The $EMP$ pathway is the most common pathway of glycolysis,which was discovered by Gustav Embden,Otto Meyerhof,and Jakub Parnas in $1930$.
This pathway is named after their initials $(E, M, P)$.

(A) Glycolysis is the process of the breakdown of glucose into two molecules of pyruvic acid.
It occurs in the cytoplasm of the cell and does not require oxygen.
The overall reaction is: $C_6H_{12}O_6 + 2NAD^+ + 2ADP + 2Pi \rightarrow 2 \text{Pyruvic acid} + 2NADH + 2H^+ + 2ATP$.
Therefore, the correct product formed is pyruvic acid.

(C) Glycolysis is the process of the breakdown of glucose into two molecules of pyruvic acid.
It occurs in the cytoplasm of the cell and is the first step of cellular respiration.
Therefore,the end product of glycolysis is pyruvic acid.

(D) Glycolysis is the partial oxidation of glucose into two molecules of pyruvic acid.
It takes place in the cytoplasm of the cell.
It is the common pathway for both aerobic and anaerobic respiration,as it does not require oxygen to proceed.

(A) Glycolysis is the process of breaking down glucose into two molecules of pyruvate.
During the conversion of glyceraldehyde-$3$-phosphate to $1,3$-bisphosphoglycerate,the enzyme glyceraldehyde-$3$-phosphate dehydrogenase catalyzes the oxidation of the substrate by removing hydrogen atoms,which are then transferred to $NAD^+$ to form $NADH + H^+$.
Therefore,oxidation is a key process occurring during glycolysis.

(B) Glycolysis is the first stage of cellular respiration that occurs in the cytoplasm of the cell.
In this metabolic pathway,one molecule of glucose $(C_6H_{12}O_6)$,which is a $6$-carbon compound,undergoes a series of enzymatic reactions to produce two molecules of pyruvic acid $(CH_3COCOOH)$,which is a $3$-carbon compound.
This process is common to both aerobic and anaerobic respiration.

(B) The breakdown of glucose in both plant and animal cells begins with a process called glycolysis.
During glycolysis,one molecule of glucose $(C_6H_{12}O_6)$ is partially oxidized into two molecules of pyruvic acid $(CH_3COCOOH)$.
This process occurs in the cytoplasm of the cell and does not require oxygen,making it the common pathway for both aerobic and anaerobic respiration.
Following glycolysis,the pyruvic acid enters the mitochondria for the Kreb's cycle (if oxygen is present) or undergoes fermentation.

(A) Glycolysis occurs in the cytoplasm of all living cells.
It is a universal metabolic pathway that does not require oxygen.
It serves as the initial stage of both aerobic and anaerobic respiration in organisms ranging from prokaryotes to eukaryotes.

(B) The first step of glycolysis is the phosphorylation of glucose.
In this step,glucose is phosphorylated by $ATP$ in the presence of the enzyme hexokinase to form glucose $6$-phosphate.
This reaction is irreversible and consumes one molecule of $ATP$.

(A) During the process of glycolysis,specifically in the step where glyceraldehyde$-3-$phosphate is converted to $1,3$-bisphosphoglycerate,the enzyme glyceraldehyde$-3-$phosphate dehydrogenase catalyzes the oxidation of the substrate.
In this reaction,electrons and protons are removed from glyceraldehyde$-3-$phosphate and are accepted by the coenzyme $NAD^+$,which gets reduced to $NADH + H^+$.
Therefore,$NAD^+$ acts as the electron acceptor during this oxidation step.

(B) The correct sequence in glycolysis is: Glucose-$6$-phosphate $\rightarrow$ Fructose-$6$-phosphate $\rightarrow$ Fructose-$1,6$-bisphosphate $\rightarrow$ $3$-phosphoglyceraldehyde $(3-PGAL)$ $\rightarrow$ $1,3$-bisphosphoglyceric acid $\rightarrow$ $3$-phosphoglyceric acid $(3-PGA)$ $\rightarrow$ $2$-phosphoglyceric acid $\rightarrow$ phosphoenol pyruvate $(PEP)$ $\rightarrow$ pyruvic acid. Among the given options,option $B$ represents the correct metabolic flow.

(C) Glycolysis is the process of breaking down glucose into two molecules of pyruvate.
This pathway is common to both aerobic respiration and anaerobic respiration (fermentation).
In both processes,glucose is converted into $3$-phosphoglyceraldehyde $(PGAL)$ and eventually into pyruvate.
After the formation of pyruvate,the pathways diverge: in fermentation,pyruvate is converted into ethanol or lactic acid,whereas in aerobic respiration,it enters the mitochondria for the Krebs cycle.

(A) Glycolysis is the process of breaking down one molecule of glucose into two molecules of pyruvic acid.
It occurs in the cytoplasm of the cell and does not require oxygen.
The end product of glycolysis is pyruvic acid,not $CO_2$ and $H_2O$.
$CO_2$ and $H_2O$ are produced during the aerobic respiration process (Krebs cycle and Electron Transport System).
Therefore,option $A$ is not true for glycolysis.

(A) $NAD$ (Nicotinamide Adenine Dinucleotide) is known as Coenzyme-$I$.
It acts as a universal hydrogen acceptor in various metabolic pathways,including glycolysis and the Krebs cycle,where it accepts hydrogen atoms to become $NADH + H^+$.

(C) During glycolysis,which is the first step of respiration,glucose is broken down into two molecules of pyruvic acid. This process occurs in the cytoplasm and does not require oxygen. Following glycolysis,pyruvic acid undergoes oxidative decarboxylation to form acetyl-CoA (a two-carbon fragment) and $CO_2$ before entering the Kreb's cycle. Therefore,the correct description is that it is broken down into two-carbon fragments and $CO_2$.

(D) The conversion of pyruvic acid into $Acetyl-CoA$ is a crucial link reaction between glycolysis and the Krebs cycle.
This process is catalyzed by the pyruvate dehydrogenase complex.
During this reaction,pyruvic acid undergoes both oxidation (removal of electrons/hydrogen) and decarboxylation (removal of a $CO_2$ molecule).
Therefore,this step is known as oxidative decarboxylation.

(B) The pentose phosphate pathway $(PPP)$,also known as the hexose monophosphate shunt,is an alternative metabolic pathway to glycolysis. In this pathway,glucose $6$-phosphate is directly oxidized to produce $NADPH$ and ribose $5$-phosphate. Since the glucose $6$-phosphate is diverted into this pathway directly,it does not undergo the standard steps of glycolysis. Therefore,glycolysis is the process that is lacking in the $PPP$.

(D) Phosphorylation is the process of adding a phosphate group to a molecule.
In biological systems,almost all phosphorylation reactions are catalyzed by specific enzymes called kinases.
In the context of standard metabolic pathways like glycolysis,steps such as the formation of fructose $1, 6$-bisphosphate from fructose $6$-phosphate or the phosphorylation of glyceraldehyde $3$-phosphate are strictly enzyme-catalyzed.
Since all the processes listed in the options are enzyme-mediated,none of them represent non-enzymatic phosphorylation.
Therefore,the correct answer is $D$.

(A) Harden and Young's ester is the historical name for Fructose-$1,6$-bisphosphate.
In the process of glycolysis,Fructose-$6$-phosphate is phosphorylated by the enzyme phosphofructokinase using $ATP$ to form Fructose-$1,6$-bisphosphate.
Therefore,it is formed from Fructose-$6$-phosphate.

(A) Glycolysis is the first phase in the breakdown of glucose.
It occurs in the cytoplasm of the cell.
During this process,one molecule of glucose $(6C)$ is broken down into two molecules of pyruvic acid $(3C)$.
This pathway is common to both aerobic and anaerobic respiration.

(C) Mitochondria are the sites of the Krebs cycle and the electron transport chain.
$Aconitase$ and $Malate \text{ } dehydrogenase$ are key enzymes involved in the Krebs cycle, which occurs within the mitochondrial matrix.
$Hexokinase$ is the enzyme responsible for the first step of glycolysis, which is the phosphorylation of glucose to glucose-$6$-phosphate.
Glycolysis occurs in the cytoplasm of the cell, not in the mitochondria.
Therefore, $Hexokinase$ is absent in the mitochondria.

(A) Glycolysis is the process of the breakdown of glucose into two molecules of pyruvic acid.
It occurs in the cytoplasm of the cell and does not require oxygen.
The overall reaction is: $Glucose + 2NAD^+ + 2ADP + 2Pi \rightarrow 2 \text{ Pyruvic acid} + 2NADH + 2H^+ + 2ATP$.
Therefore, the end product of glycolysis is pyruvic acid.

(A) The molecular formula of pyruvic acid is $CH_3COCOOH$.
It contains a methyl group $(-CH_3)$,a carbonyl group $(-CO-)$,and a carboxyl group $(-COOH)$.
Counting the carbon atoms: $1$ (in $CH_3$) + $1$ (in $CO$) + $1$ (in $COOH$) = $3$ carbons.
Therefore,pyruvic acid is a $3$-carbon compound.

(D) Glycolysis is the process of breaking down one molecule of glucose $(C_6H_{12}O_6)$ into two molecules of pyruvic acid $(CH_3COCOOH)$.
This process occurs in the cytoplasm of the cell and does not require oxygen.
Therefore,the final product of the glycolytic pathway is pyruvic acid.