CBSE Questions for Class 11 Medical Biology Respiration In Plants Quiz 4 - MCQExams.com

1. Many of the vitamins needed by our bodies are used as coenzymes to help our enzymes to do their jobs. Vitamin $$B_1$$ is also called thiamine. 
2. Thiamine pyrophosphate (TPP) is a cofactor that is present in all living systems and catalyzes several biochemical reactions. 
3. In the pyruvate dehydrogenase complex that carries out the link reaction, TPP acts as a coenzyme.

• A metabolic pathway that participates in both anabolic and catabolic pathways is called amphibolic. 
• The citric acid cycle (Krebs cycle) is a good example of the amphibolic pathway. 
• The first reaction of the cycle, in which oxaloacetate (a four-carbon compound) condenses with acetate (a two-carbon compound) to form citrate (a six-carbon compound) is typically anabolic. 
• The next few reactions are typically catabolic.

• Pyruvic acid is a product of Glycolysis, Malic acid is a product of aerobic respiration in the Kreb's cycle, and Ethyl alcohol/Lactic acid are the products of anaerobic respiration.
  
• Phosphoglyceric acid is the first stable product of photosynthesis in C$$_3$$ plants.

• A respiratory substrate is an organic substance that is used up during respiration to liberate energy. 
• Respiratory substrates include carbohydrates, proteins, fats, and organic acids. 
• Hexose monosaccharide like glucose is the most common respiratory substrate. 
• Out of the given options, hexose will be utilized first in respiration. 
• Sucrose disaccharides are first converted into monosaccharides. 
• Fats are first converted into sugars and proteins are converted into respiratory intermediates like acetyl CoA.

• During acetyl Co-A formation.
• During formation of alpha-ketoglutaric acid in Krebs cycle.
• During succinic acid formation in Krebs cycle.
  

• The end product of glycolysis, pyruvic acid is converted to acetyl-CoA by the process of oxidative decarboxylation in presence of pyruvate dehydrogenase enzyme. 
• This acetyl-CoA then enters the Krebs cycle where it is oxidized to produce energy in the form of ATP, NADH and FADH$$_2$$. 
• Beta-oxidation of fatty acid produces acetyl-CoA which then enters Krebs cycle to produce energy. 
• Hence, acetyl CoA plays an important link between glycolysis, Krebs cycle, and beta-oxidation process. 

Correct Option: D
Explanation:

• All enzymes of the TCA cycle are present in the mitochondrial matrix except succinate dehydrogenase. 
  
• Succinate dehydrogenase is tightly bound to the inner mitochondrial membrane in eukaryotes and to the plasma membrane in prokaryotes.
  
• It has three different iron-sulfur clusters and one covalently bound FAD. Before entering ETS in mitochondria, electrons pass from succinate through the FAD and iron-sulfur centres.

• Two molecules of $$CO_2$$  are given off during two decarboxylation reactions.
• One molecule of $$ATP$$ is formed.
• Three molecules of $$NADH$$ are produced.
• One molecule of $$FADH_2$$ is produced.
  

• Most of the energy in the cell is liberated by the oxidation of carbohydrates when pyruvic acid is converted to $$CO_2$$ and $$H_2O$$. 
• Pyruvate when enters the Krebs cycle it generates a lot of energy in the form of NADH,  $$FADH_2$$ and GTP, also produces carbon dioxide and water as the by-product through several steps.

Correct Option: A
Explanation:

Glycolysis involves the breakdown of glucose into two molecules of pyruvate with the net release of 8 ATP.

Correct Option: C
Explanation:

• In the process of respiration, pyruvic acid is broken down into carbon fragments and $$CO_2$$.
• Pyruvic acid in aerobic respiration is broken down slowly in a complex chain of events, called the Krebs cycle.
• During this cycle, 34 more ATP molecules are produced.
• Before entering into the Krebs cycle, one pyruvate is broken down into two acetyl-CoA and one carbon dioxide is released.
  Hence, in respiration pyruvic acid is broken down into two molecules of Carbon Dioxide.

$$\textbf{Correct Option C}$$

$$\textbf{Solution}$$

$$\bullet$$ During the process of respiration there are various cycles that are involved. 

$$\bullet$$ $$\textbf{Option A}$$ During anaerobic respiration which occurs in the absence of oxygen, two molecules of ATP is produced which is a very small amount.

$$\bullet$$ $$\textbf{Option B}$$ During the process of glycolysis, that happens in the anaerobic respiration around 8 ATP molecules are produced.

$$\bullet$$ $$\textbf{Option C}$$ During the Krebs cycle 30 ATP molecules are produced which is the largest amount of phosphate pound energy produced.

$$\bullet$$ $$\textbf{Option D}$$ The link reaction does not produce any energy in the form of ATP. In this reaction pyruvate is converted into acetyl coenzyme A

So, the correct option is C.