Pentose Phosphate Pathway - Class XII

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).

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. 

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. 

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 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. 

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

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.

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.

The Pentose Phosphate Pathway (PPP) produces Erythrose-4-phosphate, which is a precursor for aromatic amino acids and lignin biosynthesis. It occurs in the cytosol and in plastids (such as chloroplasts), and it generates NADPH as a primary reducing equivalent.

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.

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

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. 

• 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'.

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.

Answer is B.

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). 

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.

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

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.

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.

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

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'.

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.