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Alternative to glycolysis - class-XII

Description: alternative to glycolysis
Number of Questions: 26
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Tags: bio-chemistry carbohydrate metabolism respiration
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HMP shunt was discovered by 

  1. Horecker and coworkers

  2. Warburg and Dickens

  3. Blackman

  4. M.Calvin


Correct Option: B
Explanation:

Hexose Monophosphate Pathway (HMP) is an alternative pathway of glucose break down found in animal tissues like liver, mammary glands, adrenal cortex, leucocytes and in many plant tissues. The pathway was first discovered by Warburg et. at. (1953) and Dickens (1938).

So, the correct answer is option B.

The pentose monophosphate shunt is more advantageous than Krebs cycle as

  1. It yields more ATP

  2. Ribose sugar is released, which helps in nucleic acid formation

  3. It releases more oxygen

  4. It utilizes less oxygen


Correct Option: B
Explanation:

Pentose phosphate pathway is also known as HMP shunt. This pathway provides an alternative route for carbohydrate breakdown. HMP shunt produces some glycolytic intermediates like glyceraldehyde-3-phosphate and fructose-6-phosphate. These intermediates can directly involve in the glycolysis pathway and then in the Krebs cycle. The cycle provides ribose sugar which can be used for the synthesis of nucleic acids. This pathway is considered as advantageous since the ribose sugar is made available. 

Thus, the correct answer is option B. 

Phosphogluconate shunt occurs in

  1. Mitochondria

  2. Chloroplasts

  3. Cytoplasm

  4. Both A and B


Correct Option: C
Explanation:

The reactions of hexose monophosphate shunt occur exclusively in the cytoplasm and is an additional pathway of glucose metabolism which starts with glucose-6-phosphate. About 10-25% of glucose is metabolised by this pathway. In plants, it occurs both in cytosol and plastids. This pathway involves both oxidative and nonoxidative steps. The oxidative steps generate NADPH and ribose-5-phosphate and then non-oxidative steps convert ribose-5-phosphate back into glucose-6-phosphate which can be further utilized for NADPH generations by means of oxidative steps. 

Thus, the correct answer is option C. 

A respiratory cycle where mainly ${NADPH _2}$ are produced is 

  1. Calvin cycle

  2. Kreb's cycle

  3. EMP pathway

  4. HMP shunt


Correct Option: D
Explanation:

During Calvin cycle, $NADH _2$ are not produced. 
During Krebs cycle, 2 $NADH _2$, 1 $FADH _2$, 1GTP are produced. 
During EMP pathway 2 NADH, 2 ATP are produced. 
During HMP pathway, $NADPH _2$ are produced. So, in respiratory cycle  mainly $NADPH _2$ are produced is HMP pathway. Thus, option D is correct.

Pentose phosphate pathway is a mode of

  1. Amphibolic pathway

  2. Anabolic pathway

  3. Aerobic respiration

  4. Anaerobic respiration


Correct Option: C
Explanation:

Pentose phosphate pathway is an alternative pathway to glycolysis which involves the oxidation of glucose-6-phosphate to 6-phosphogluconic acid which in turn gets converted into pentose phosphates. This pathway involve the direct oxidation of glucose-6-phosphate without entering glycolysis and hence is termed as direct oxidation. 

Thus, the correct answer is option C. 

Which of the following is generated in the oxidative phase of pentose phosphate pathway?

  1. NADPH

  2. FADH

  3. GTP

  4. None of the above


Correct Option: A
Explanation:

The Pentose Phosphate Pathway is an alternative pathway to glycolysis and TCA cycle. It occurs in both prokaryotes and eukaryotes in their cytoplasm

Glucose is broken down by a series of pathways.
The pathway has 2 phases- Oxidative and Non-oxidative.
In the oxidative stage, there are 2 steps where NADP⁺ gets converted to NADPH.
1. Glucose 6-phosphate converts to 6-phosphogluconolactone
2. 6-phosphogluconate converts to Ribulose 5- phosphate
So, the correct option is 'NADPH'

Pentose phosphate pathway takes place only in the

  1. Cytoplasm

  2. Mitchondria

  3. Peroxisome

  4. Chloroplast


Correct Option: A
Explanation:

The pentose phosphate pathway is a metabolic pathway which is carried out in most of the organisms. This pathway occurs parallel to glycolysis. This pathway produces pentoses from glucose 6-phosphate. The pathway takes place in the cytoplasm in most of the organisms. In the case of plants, there are certain reactions which occur in the plastids.

Thus, the correct answer is option A. 

Pentose phosphate pathway takes place only in the

  1. Cytoplasm.

  2. Mitochondria.

  3. Peroxisome.

  4. Chloroplast.


Correct Option: A
Explanation:
The pentose phosphate pathway is a metabolic pathway which is carried out in most of the organisms. This pathway occurs parallel to glycolysis. This pathway produces pentoses from Glucose 6-phosphate. The pathway takes place in the cytoplasm in most of the organisms. In the case of plants, there are certain reactions which occur in the plastids.
Thus, the correct answer is option A. 

An enzyme used in pentose phosphate pathway is

  1. RUBP.

  2. Aldolase.

  3. Pyruvate kinase.

  4. Phosphogluconate dehydrogenase.


Correct Option: D
Explanation:

In the pentose phosphate pathway 6-Phosphogluconate dehydrogenase (6PGD) is an enzyme that produces NADPH by converting 6-phosphogluconate to ribulose 5-phosphate. NADPH is used for lipid production. Thus the correct answer is option D.

Consider the following statements.


a. The Pentose Phosphate Pathway supplies Erythrose-$4$-Phosphate which is the starting material the synthesis on lignin.
b. The Pentose Phosphate pathway also occurs in plastids.
c. NADPH is generated by the Pentose phosphate pathway

Which of the statements given are correct?

  1. $a$ and $b$ only

  2. $a$ and $c$ only

  3. $b$ and $c$ only

  4. $a, b$ and $c$


Correct Option: A

The substrate for pentose phosphate pathway is

  1. Glucose 6-phosphate.

  2. Glucose 1-phosphate.

  3. Fructose 6-phosphate.

  4. Fructose 1-phosphate.


Correct Option: A
Explanation:

Pentose Phosphate Pathway runs parallel to glycolysis and takes place in the cytoplasm. The oxidation steps, utilizing glucose-6-phosphate (G6P) as the substrate, occur at the beginning of the pathway and are the reactions that generate NADPH and also give five carbon compound for glycolysis.

So the correct option is 'Glucose 6-phosphate'.

Which one of the following produces more energy per glucose molecule?

  1. Alcoholic fermentation

  2. Glycolysis

  3. Pentose phosphate pathway

  4. Lactic acid fermentation


Correct Option: C
Explanation:

Glycolysis is a common pathway between the aerobic and anaerobic respiration. The net amount of ATP formed during glycolysis is two.

Alcoholic fermentation and lactic acid fermentation are both of pathways involved in the anaerobic respiration in which the pyruvic acid formed after glycolysis is converted into lactic acid or ethanol and carbon dioxide. The energy released during anaerobic respiration is much less as compared to the aerobic respiration.
So the correct option is, 'pentose phosphate pathway'

Which of the following pairs of structure and functions are correctly matched?
a. Tendril- Climbing
b. Penumatophore - Respiration
c. Stratospheric - checking UV or beta
d. Ozone shield - UV rays
Select the correct answer using the codes given.

  1. $2$ and $3$ only

  2. $1$ and $2$ only

  3. $1$ and $3$ only

  4. $1, 2$ and $3$


Correct Option: A

In hexose monophosphate shunt, the net formation of ATP molecules is

  1. 36

  2. 35

  3. 38

  4. 34


Correct Option: A
Explanation:

Hexose monophosphate shunt is an alternative pathway to glycolysis or the tricarboxylic acid cycle for glucose oxidation. It occurs in the cytoplasm and has two phases; the oxidative phase and the non-oxidative phase. 

This is the only process that generates reduced NADPH₂ which act as the reducing agent in the biosynthetic processes.
6 glucose molecules that enter hexose monophosphate shunt, produces 12 NADPH₂ and 6 carbon dioxide.
12 NADPH₂ molecules when undergo ETS forms  36 molecules of ATP.
So, the correct option is '36'


Which of the following is not a pathway that relates to generation of ATP?

  1. Pentose phosphate shunt

  2. Embden-Meyerhof pathway

  3. Oxidative-phosphorylation

  4. Photosynthesis


Correct Option: A
Explanation:

  • Pentose phosphate shunt is the pathway that is used for the synthesis of a 5 carbon molecules such as ribose and deoxyriose which can be used for the synthesis of nucleotides, no ATP is produced during this reaction.
  • EMP pathway is the glycolysis process where 2 ATP are produced at the end of the reaction.
  • Oxidative phosporylation is the pathway that is used to reduce the NADH and FADH for the formation of ATP
  • And photosynthesis is the pathway in the plant that is used for the production of the carbohydrates that are used in the catabolic pathway for the synthesis of the ATP in cellular respiration.
  • Therefore the correct answer is option is 'Pentose phosphate shunt'.











Production of $NADPH _2$ is not linked with ATP generation in

  1. Photorespiration

  2. Light recation

  3. Hexose monophosphate pathway

  4. Dark reaction


Correct Option: C
Explanation:

Hexose monophosphate pathway (HMP) or pentose phosphate shunt is an alternate glucose metabolism that occurs in adipose tissues, liver, erythrocytes, testes, adrenal glands, mammary glads etc. This pathway is performed to generate the $NADPH _2$ to facilitate the cholesterol synthesis, steroid and lipid production and fatty acid synthesis. Thus signifying that HMP pathway readily takes place in tissues associated with lipogenesis like liver and adipose tissue. It is not linked with ATP generation. Also, the ribose sugars generated are used in DNA and RNA and many nucleotides like $ATP$, $FADH _2$ $CoA$ etc.

Photorespiration, light reaction and dark reaction are associated with phosphorylation.
Hence, the correct answer is 'Hexose monophosphate pathway'

Match the column I and II-

Column-I Column-II Site of pathway
(A) Fatty acid oxidation (p) Cytoplasm
(B) Pyruvate oxidation (q) Mitochondrial matrix
(C) Fatty acid synthesis (r) Mitochondrial inner membrane
(D) Pentose phosphate pathway (s) Glyoxysome
  1. A $\rightarrow$ p, B$\rightarrow$ q, C$\rightarrow$ r, D$\rightarrow$ s

  2. A $\rightarrow$ q, B$\rightarrow$ p, C$\rightarrow$ p, D$\rightarrow$ p

  3. A$\rightarrow$ p, B$\rightarrow$ r, C$\rightarrow$ q, D$\rightarrow$ s

  4. A $\rightarrow$ p, B$\rightarrow$ q, C$\rightarrow$ q, D$\rightarrow$ p


Correct Option: B
Explanation:

Answer is B.


A. Fatty acid oxidation - (q) Mitochondrial matrix

B. Pyruvate oxidation  -(p) Cytoplasm
C. Fatty acid synthesis - (p) Cytoplasm
D. Pentose phosphate pathway-(p) Cytoplasm. 

Warburg-Dickens pathway is also known as

  1. P.P.P.

  2. TCA cycle.

  3. EMP pathway.

  4. None of the above.


Correct Option: A
Explanation:

Pentose phosphate pathway (PPP) is variously called as Warburg-Dickens pathway and hexose monophosphate shunt. This metabolic pathway had been discovered through a number of experiments of Lippman, Warburg (1935) and Dickens (1938). 

Oxidation of glucose to CO$ _2$ and water occurs during

  1. Glycolysis

  2. Pentose phosphate pathway

  3. Krebs cycle

  4. All of the above


Correct Option: B
Explanation:

Pentose phosphate pathway is the only pathway in which glucose is completely oxidised to CO$ _2$ and H$ _2$O. It is also called HMP (hexose monophosphate shunt) as it is an alternate pathway to glycolysis. The primary substrate glucose is first phosphorylated to glucose-6-phosphate in presence of G6PD by consuming 1 ATP. A net gain of 35 ATP is achieved by oxidation of 1 molecule of glucose.

So the answer is 'Pentose phosphate pathway'.

Which of the following enzyme helps in conversion of 6-phosphogluconate to ribulose-5-phosphate?

  1. 6-phosphogluconate dehydrogenase

  2. Hexokinase

  3. Alpha-ketoglutarate

  4. None of the above


Correct Option: A
Explanation:

This conversion takes place during the oxidative phase of the pentose phosphate pathway.

Here, When 6-phosphogluconate converts to ribose 5-phosphate, the enzyme used is 6-phosphogluconate dehydrogenase. 
In this step an NADP⁺ converts to NADPH and CO₂ is released.
So, the correct option is '6-phosphogluconate dehydrogenase.'

 Erythrose 4-phosphate is used in synthesis of 

  1. Carbohydrates.

  2. Aromatic amino acid.

  3. NADH.

  4. Erythrose-4-phosphate.


Correct Option: B
Explanation:

Erythrose-4-phosphate is an intermediate produced in the pentose phosphate pathway.  It is involved in the biosynthesis of aromatic amino acids. All the carbons in phenylalanine and tyrosine are produced from erythrose-4-phosphate and phosphoenolpyruvate. Phenylalanine and tyrosine are aromatic amino acids. Thus the correct answer is option B.

Which of the following cellular metabolic processes can occur both in the presence or absence of ${O} _{2}$?
  1. Glycolysis

  2. Fermentation

  3. TCA cycle

  4. Electron transport coupled with chemiosmosis


Correct Option: A
Explanation:

Glycolysis is an oxidative process in which one molecule of glucose is partially oxidised into two molecules of pyruvate in a series of enzyme catalysed reactions. Glycolysis, the major pathway for glucose metabolism, occurs in the cytosol of cells. It is a unique pathway that occurs aerobically as well as anaerobically and does not involve molecular oxygen.

Which one requires oxygen?

  1. Fermentation.

  2. EMP pathway.

  3. Pentose phosphate pathway.

  4. None of the above.


Correct Option: D
Explanation:

All the processes occur in the absence of oxygen i.e., anaerobic condition. 

So the correct option is 'None of the Fermentation or EMP pathway or Pentose phosphate pathway.'

Which is not pentose?

  1. Erythrose

  2. Ribose

  3. Xylose

  4. Arabinose


Correct Option: A
Explanation:

The pentose sugars ribose and deoxyribose are part of the nucleotides that make up the crucial nucleic acids like DNA and RNA. So the correct option is 'Erythrose'.

Which one of the following hormone never reaches to cytoplasm?

  1. Estrogen

  2. FSH

  3. Progesterone

  4. Testosterone


Correct Option: B
Explanation:

FSH is a proteinaceous hormone. It does not enter its target cells, thus, it never reaches to cytoplasm. Instead, it binds to the receptor present on the cell membrane and activates a membrane bound enzyme that causes conversion of ATP to cAMP. This then alters the activities of enzyme in the cytoplasm.

Last ${e}^{-}$ acceptor during ETS is 
  1. ${O} _{2}$

  2. cyt $a$

  3. cyt ${a} _{2}$

  4. cyt ${a} _{3}$


Correct Option: A
Explanation:

In electron transport chain, there are 7 electron acceptors, which are as follows $Co-Q\rightarrow Cyt\,\, b\rightarrow Cyt \,\,{c} _{1} \rightarrow Cyt \,\,c\rightarrow Cyt \,\,a\rightarrow Cyt \,\,{a} _{3}\rightarrow{O} _{2}$. Oxygen is the ultimate electron acceptor. These electron acceptors are present in a specific sequence along inner mitochondrial membrane.

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