Q: One molecule of NADH\$_{2}\$ on oxidation yields ............... ATP molecules.

The NADH\$_2\$ and the FADH\$_2\$ are produced during the cycles of respiration. These molecules are produced during the glycolysis and the Krebs cycle. These molecules are oxidized in the process of electron transport system. This is the system in which the electrons is donated from one donor to acceptor. These products are oxidized and the protons are used for creating a gradient which is used in the synthesis of ATP. NADH\$_2\$ transfers the electrons to the complex I and then transfers the electrons to the complex II. This results in more number of protons which are pumped by ATP synthase. So, the more protons will result in the production of 3 ATPs.Thus, the correct answer is option C.

Question 1

Give the schematic representation of Glycolysis

Accepted Answer

Glycolysis - (i) In this process, glucose undergoes partial oxidation to form two molecules of pyruvic acid. (ii) In plants, this glucose is derived from sucrose which converted into glucose and fructose by the enzyme, invertase and these two monosaccharides readily enter the glycolytic pathway. (iii) Glucose and fructose are phosphorylated to give rise to glucose-6-phosphate by the activity of the enzyme hexokinase. (iv) This phosphorylated form of glucose then isomerises to produce fructose-6-phosphate. (v) A chain of ten reactions, under the control of different enzymes, takes place to produce pyruvate from glucose. (vi) Utilization of ATP during glycolysis           (a)During the conversion of glucose into glucose-6-phosphate.           (b) During the conversion of fructose-6-phosphate to fructose-1, 6-diphosphate.

Question 2

Discuss "The respiratory pathway is an amphibolic pathway".

Accepted Answer

The respiratory pathway is an amphibolic pathway as it involves both anabolism and catabolism. It is catabolic pathway as, during this process, various complex molecules are broken down into the simpler molecule to obtain energy. Carbohydrates are broken down into glucose. Fats are broken down into fatty acids and glycerol. Fatty acids further get converted into acetyl CoA. Proteins are broken down into amino acids. During synthesis of fatty acids, acetyl CoA is withdrawn from the respiratory pathway. Similarly, during synthesis of proteins, respiratory substrate amino acid is withdrawn. Hence, it is also an anabolic pathway.

Question 3

How many ATP molecules are produced in Krebs cycle through substrate level phosphorylation?

Accepted Answer

Kreb's cycle only produces 1 molecule of ATP from every pyruvate molecule during the conversion of succinyl-CoA to succinate in the presence of enzyme Succinyl CoA synthetase. One molecule of glucose undergoes glycolysis to produce 2 pyruvate molecules which enter Kreb's cycle simultaneously.Thus, overall 2 ATP are produced from Kreb's cycle through substrate-level phosphorylation when one glucose undergoes aerobic respiration.So, the correct answer is option E.

Question 4

Number of ATP molecules produced from 1 glucose molecule in aerobic respiration

Accepted Answer

Product Molecule ATP Glycolysis 2 ATP2NADH 8ATP Krebs cycle NADH 3 (in two cycle) 18 ATP FADH$_2$ 4 (in two cycle) 4 ATP GTP 2 (in two cycle) 2ATP Oxidative decarboxylation 2 NADH (in two cycle) 6ATP Total  38

Question 5

Give the schematic representation of an overall view of Krebs cycle.

Accepted Answer

Question 6

Why is ATP called energy currency of cells?

Accepted Answer

ATP is known as adenosine triphosphate, and it is a molecule containing carbon, hydrogen, nitrogen, oxygen and phosphorus. ATP is the energy currency of the cell because, it is the most preferred energy molecule in the cell. Its preference is due to the following factors:1.&#9;It donates its phosphoryl groups to release energy.2.&#9;On hydrolysis, it releases a high negative Gibbs free energy which can be used to drive many important biosynthetic reactions in metabolic pathways.3. The presence of adenine and ribosyl groups provide additional features for attachment to enzymes so it is able to regulate enzymatic activities.

Question 7

The process Glycolysis occurs in

Accepted Answer

Sequence of chemical reactions catalyzed by cellular enzymes occurring in the cytoplasm of cells that breaks down glucose, that releases energy stored as ATP is called glycolysis.One molecule of glucose makes two molecules of pyruvate and two molecules of ATP. The pyruvate either enters into the tricarboxylic acid cycle (mitochondrial matrix) in presence of adequate oxygen or is fermented into lactic acid or ethanol. Thus, glycolysis produces both ATP for cellular energy requirements and building blocks for synthesis of other cellular products.This process occurs in all organisms, and is responsible for converting glucose to pyruvate and generating ATP in the process. Glycolysis does not require oxygen to function.

Question 8

How many ATP molecules are produced from the complete oxidation of a molecule of active acetate or acetyl CoA ?

Accepted Answer

Glucose undergoes glycolysis to form 2 molecules of pyruvate. The pyruvate molecule is converted to 2 molecules of acetyl-CoA. Each molecule of acetyl-CoA enters the Krebs cycle.1 NADH (3 ATP) molecule is formed when the isocitrate is converted to oxalosuccinate.1 NADH (3 ATP) is formed during the conversion of ketoglutarate to succinyl-CoA.1 GTP/ATP is produced when sunnicyl-CoA is converted to succinic acid.1 FADH$_2$2 (2 ATP) is produced when succinc acid is converted to fumaric acid.1 NADH (3 ATP) is formed when malate is converted to oxaloacetate. So, the correct answer is 12 ATP. Thus, the correct answer is option C.

Question 9

One molecule of NADH$_{2}$ on oxidation yields ............... ATP molecules.

Accepted Answer

The NADH$_2$ and the FADH$_2$ are produced during the cycles of respiration. These molecules are produced during the glycolysis and the Krebs cycle. These molecules are oxidized in the process of electron transport system. This is the system in which the electrons is donated from one donor to acceptor. These products are oxidized and the protons are used for creating a gradient which is used in the synthesis of ATP. NADH$_2$ transfers the electrons to the complex I and then transfers the electrons to the complex II. This results in more number of protons which are pumped by ATP synthase. So, the more protons will result in the production of 3 ATPs.Thus, the correct answer is option C.

Question 10

A Krebs cycle intermediate, which act as a raw material for chlorophyll production is synthesized after

Accepted Answer

Succinyl coenzyme A is utilized in the synthesis of porphyrin rings, used in heme manufacture and chlorophyll biosynthesis. It is synthesized from &#945;-ketoglutarate by &#945;-ketoglutarate dehydrogenase through oxidative decarboxylation. During this process, coenzyme A is added, and H$^{+}$ and CO$_{2}$ are released along.&#945;-Ketoglutarate + NAD$^{+}$ + CoA-SH &#8594; Succinyl-CoA + NADH + H$^{+}$ + CO$_{2}$So, the correct option is 'Dehydrogenation'.