These notes cover Chapter 14, Respiration in Plants, for CBSE Class 11 Biology. They explain the core concepts of aerobic and anaerobic respiration, distinguishing them by the presence or absence of oxygen in the breakdown of food. Important terms such as ATPSynthetase, cytochromes, and dehydrogenases are defined. The notes meticulously outline the stages of aerobic respiration: Glycolysis (EMP pathway), Oxidative Decarboxylation, the Tri-Carboxylic Acid (Kreb's) Cycle, and Oxidative Phosphorylation. Glycolysis, taking place in the cytoplasm, converts glucose to pyruvic acid, producing a net of 2 ATP. Oxidative decarboxylation transforms pyruvic acid into Acetyl CoA. The Kreb's cycle, occurring in the mitochondrial matrix, further processes molecules, generating NADH, FADH2, and ATP. Finally, Oxidative Phosphorylation, driven by the Electron Transport System on the inner mitochondrial membrane, synthesizes ATP using a proton gradient, with oxygen acting as the terminal electron acceptor. This chapter is vital for grasping plant respiration and for exam preparation.
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Aerobic respiration : Complete oxidation of organic food in presence of
oxygen thereby producing CO
, water and energy.
Anaerobic respiration : Incomplete breakdown of organic food to liberate 2 energy in the absence of oxygen.
ATPSynthetase : An enzyme complex that catalyses synthesis of ATP during
oxidative phospho-relation.
Biological oxidation : Oxidation in a series of reaction inside a cell.
Cytochromes : A group of iron containing compounds of electron transport
system present in inner wall of mitochondria.
Dehydrogenase : Enzyme that catalyses removal of H atom from the
substrate.
Electron acceptor : Organic compound which recieve electrons produced
during oxidation-reduction reactions.
Electron transport : Movement of electron from substrate to oxygen through
respiratory chain during respiration.
Fermentation : Breakdown of organic substance that takes place in certain and ethanol.
microbe like yeast under anaerobic condition with the production of CO.
Glycosis : Enzymatic breakdown of glucose into pyruvic acid that occurs in
the cytoplasm.
Oxidative phosphorylation : Process of formation of ATP from ADP and
Pi using the energy from proton gradient.
Respiration : Biochemical oxidation food to release energy.
Respiratory Quotient : The ratio of the volume of CO
produced to the
volume of oxygen consumed.
Proton gradient : Difference in proton concentration across the tissue
membrane.
Mitochondrial matrix : The ground material of mitochondria in whichpyruvic acid undergoes aerobic oxidation through Kreb’s cycle.
Abbreviations
ATP ? Adenosine tri phosphate
ADP ? Adenosine di phosphate
NAD ? Nicotinamide Adenine dinucleotide
NADP ? Nicotinamide Adenine dinucleotide Phosphate
NADH ? Reduced Nicotinamide Adenine dinucleotide
PGA ? Phosphoglyceric acid
PGAL ? Phospho glyceraldehyde
FAD ? Flavin adenine dinucleotide
ETS ? Electron transport system
ETC ? Electron transport chain
TCA ? Tricarboxylic acid
OAA ? Oxalo acetic acid
FMN ? Flavin mono nucleotide
PPP ? Pentose phosphate pathway
The overall mechanism of aerobic respiration can be studied under the
following steps :
(A) Glycolysis (EMP pathway)
(B) Oxidative Decarboxylation
(C) Kreb’s cycle (TCA-cycle)
(D) Oxidative phosphorylation
Glycolysis : The term has originated from the Greek word
glycos =
glucose
lysis = splitting or breakdown means breakdown of glucose molecule.
• It is also called Embeden-Meyerhof-Paranus pathway. (EMP pathway)
• It is common in both aerobic and anaerobic respiration.
• It takes place outside the mitochondria, in the cytoplasm.
• One molecule of glucose (Hexose sugar) ultimately produces two mol-
ecules of pyruvic acid through glycolysis.
• During this process 4 molecules of ATP are produced while 2 molecules
of ATP
are utilised.
Thus net gain of ATP
is of 2 molecules.
Oxidative decarboxylation : Pyruvic acid is converted into Acetyle CoA
in presence of pyruvate dehydrogenase complex.
Tri Carboxylic Acid Cycle (Kreb’s cycle) or Citric acid Cycle : This
cycle starts with condensation of acetyle group with oxaloacitic acid and water
to yield citric acid which undergoes a series of reactions.
• It is aerobic and takes place in mitochondrial matrix.
• Each pyruvic acid molecule produces 4 NADH + H + , one FADH
, one
ATP.
• One glucose molecule has been broken down to release CO
and eight
molecules of NADH + H + , two molecules of FADH
and 2 molecules
of ATP. 2 Electron transport system and oxidative phosphorylation : The metabolic
pathway through which the electron passes from one carrier to another, is called
Electron transport system and it is present in the inner mitochondrial membrane.
ETS comprises of the following :
(i) NAD and NADH + H
(ii) FAD and FADH
(iii) UQ
(iv) Cyt b, Cyt c 1 2 + , Cyt c, Cyt a and Cyt a . Oxygen acts as final hydrogen acceptor. Oxidative phosphorylation takes 3 place in elementary particles present on the inner membrane of cristae of mitochondria.
Synthesis of ATP
from ADP and Pi using energy from proton gradient is called oxidative phosphorylation. In this process O
acceptor and it get reduced to water. 2 2 2 is the ultimate electron
Total ATP Production |
|
Process |
Total ATP produced |
| 1. Glycolysis | 2ATP + 2NADH (6ATP) = 8ATP |
| 2. Oxidative decarboxylation | 2NADH (6ATP) = 6ATP |
| 3. Kreb’s Cycle | 2GTP (2ATP) + 6NADH22 (18ATP) + 2FADH (4ATP) = 24ATP22 |
Aerobic respiration is the complete oxidation of organic food in the presence of oxygen, producing CO2, water, and energy.
Anaerobic respiration is the incomplete breakdown of organic food to release energy in the absence of oxygen.
Glycolysis occurs in the cytoplasm and is common to both aerobic and anaerobic respiration.
The net gain of ATP from one molecule of glucose during glycolysis is 2 molecules.
The Kreb's cycle takes place in the mitochondrial matrix.
Oxygen acts as the final electron acceptor in the Electron Transport System (ETS) during aerobic respiration.
The Respiratory Quotient is the ratio of the volume of CO2 produced to the volume of oxygen consumed during respiration.
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