Class 11 Biology - PUNJAB
Respiration in Plants
The chapter 'Respiration in Plants' in Class 11 Biology explores how plants break down complex organic compounds, mainly glucose, to release energy in the form of ATP for various cellular activities. You will learn about both aerobic and anaerobic respiration, starting with glycolysis in the cytoplasm, followed by the Krebs cycle and oxidative phosphorylation in the mitochondria. Understanding the amphibolic pathway and respiratory quotient (RQ) is crucial. For PSEB board exams, this chapter is high-scoring and frequently features questions on metabolic pathways, ATP calculations, and cyclic processes, making a clear grasp of the NCERT/PSEB textbook diagrams essential for success.
Start Learning FreeKey Concepts
Glycolysis
Also known as the EMP pathway, it takes place in the cytoplasm where one molecule of glucose is broken down into two molecules of pyruvate, yielding a net gain of 2 ATP and 2 NADH.
Krebs Cycle
Also called the Citric Acid Cycle, it occurs in the mitochondrial matrix where acetyl-CoA is completely oxidized to carbon dioxide, producing NADH, FADH2, and substrate-level ATP.
Electron Transport System (ETS)
Located on the inner mitochondrial membrane, electrons from NADH and FADH2 pass through a series of carriers, driving proton pumping to generate a gradient that synthesizes ATP via ATP synthase.
Respiratory Quotient (RQ)
It is the ratio of the volume of CO2 evolved to the volume of O2 consumed during respiration, which helps determine the type of respiratory substrate being used.
Amphibolic Pathway
Respiration is not just catabolic (breakdown); it is amphibolic because it also involves anabolic (biosynthetic) pathways where respiratory intermediates are used to synthesize fats and proteins.
Important Formulas
Board Exam Info
In the Punjab School Education Board (PSEB) Class 11 Biology exams, this chapter typically carries around 4 to 6 marks. Expect 1-mark objective questions, 2-mark short notes on glycolysis or Krebs cycle, and 3 to 5-mark long questions requiring a flowchart explanation of aerobic respiration or the difference between aerobic and anaerobic respiration.
Frequently Asked Questions
Why is the respiratory pathway considered an amphibolic pathway?
It acts as a catabolic pathway when breaking down substrates like glucose for energy, but it also acts as an anabolic pathway when its intermediates (like Acetyl-CoA or alpha-ketoglutarate) are withdrawn to synthesize fatty acids, amino acids, and chlorophyll.
What is the net gain of ATP in glycolysis?
Although 4 ATP molecules are produced during glycolysis, 2 ATP molecules are consumed in the initial steps, resulting in a net gain of 2 ATP and 2 NADH molecules.
What is the difference between aerobic respiration and fermentation?
Aerobic respiration requires oxygen and completely oxidizes glucose into CO2 and water yielding high energy (36-38 ATP), whereas fermentation occurs in the absence of oxygen, incompletely breaks down glucose into ethanol or lactic acid, and yields only 2 ATP.
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