CBSE Questions for Class 11 Medical Biology Respiration In Plants Quiz 3 - MCQExams.com

• Organic acids have more volume of $$CO_2$$ liberated during respiration than the volume of $$O_2$$ used. Therefore, the RQ value will be greater than one. E.g., the RQ of oxalic acid is 4.
• RQ of fats and proteins is less than one while that of carbohydrates is one.

• Respiration is an oxidative process in which respiratory substrates are oxidized to liberate energy inside the living cells.
  
• The respiratory quotient is the value, which depends upon the oxidation of the respiratory substrate. 
• It is calculated by the amount of $$CO_2$$ eliminated to that of $$O_2$$ consumed.
• Different respiratory substrates have different numbers of carbon and oxygen atoms in their molecules. 
• So, during respiration, the amount of carbon dioxide evolved from per gram weight of the substrate also differs.
  

• When incomplete oxidation of carbohydrates takes place RQ is zero. In such cases, oxygen absorbed does not oxidize the carbohydrates completely to CO$$_2$$ and water but produces intermediate products of partial oxidation.
  
• This occurs especially in the respiration of succulent plants, such as cacti (Opuntia). In such plants respiration of carbohydrates occurs at night when stomata are open which results in the production of organic acids that utilize O$$_2$$ but do not evolve CO$$_2$$.

• Anaerobic respiration involves the incomplete breakdown of glucose. 
• It releases around 5% of the energy released by aerobic respiration, per molecule of glucose. 
• In yeast, it can be observed, as alcoholic fermentation. 
• A biological process in which molecules such as glucose, fructose, and sucrose are converted into cellular energy and thereby produce ethanol and carbon dioxide as metabolic waste products.

• Fermentation is an energy-releasing process in which substrates like sugar is oxidized into organic acids or alcohol without an external electron acceptor.
• The final electron acceptor is either acetaldehyde or pyruvate. 
• Aerobic respiration is a process in which energy is produced in the presence of oxygen.
• Glycolysis is a process of converting glucose into two molecules of pyruvate.
• Photorespiration is a process in which the RuBisCO enzyme oxygenates RuBP by wasting some amount of energy.

1. Anaerobic respiration is the respiration which occurs in the absence of oxygen. It is carried out by yeast and some bacteria. In this, glucose breaks down into pyruvates in absence of oxygen.

   Glucose breaks down into ethanol, carbon dioxide and gives two molecules of ATP.

   $$C_6H_{12}O_6$$→ $$C_2H_5OH$$+ $$CO_2$$

• Fermentation is a metabolic process, that converts sugar to acids, gases and alcohol. 
• It occurs in yeast and bacteria, but also in oxygen-starved muscle cells, as in the case of lactic acid fermentation. 
• It could be represented by the equation for alcoholic fermentation:

Correct Option: D

Explanation:

• Fed-batch fermentation is a microbiological operation in which one or more substrates (such as sugar/nutrients) are fed or supplied to the bioreactor during the growth phase, and the product remains in the bioreactor until the end of the reaction.
• The fed-batch method is used to purify enzymes by adding nutrients/sugar to the mechanism on a regular basis.

Hence Continuous addition of sugars in fed-batch fermentation is done to purify enzymes.

• Under anaerobic conditions, pyruvic acid is either converted to lactate in lactate fermentation or ethanol in alcohol fermentation. 
• During alcohol fermentation, pyruvic acid is first converted to acetaldehyde in presence of the enzyme pyruvate decarboxylase. 
• The acetaldehyde is then converted into ethyl alcohol by the enzyme alcohol dehydrogenase. 

Correct option B

Explanation for the correct option:

• Dehydrogenation is a chemical reaction in which hydrogen from a molecule is removed.
•  It is the reversal of the hydrogenation process.
• Two protons and two electrons are lost in the process.

Correct Option: A

Explanation:

During glycolysis, electrons are extracted by NAD+ during the oxidation of glyceraldehyde 3-phosphate to 1, 3-bisphosphoglycerate, which generates NADH + H+.

Hence, NAD+ removes electrons in glycolysis.

• The process of ATP formation is phosphorylation. 
• Substrate-level phosphorylation is a metabolism reaction that results in the production of ATP or GTP by the transfer of a phosphate group from a substrate directly to ADP or GDP.
  
• In the process of glycolysis, there is a net gain of 2 ATP molecules through substrate-level phosphorylation.