CLASS 11TH BIOLOGY CHAPTER- 14 RESPIRATION IN PLANTS NCERT QUICK REVISION NOTES FOR NEET AND CBSE EXAM
RESPIRATION IN PLANTS
¶ Anaerobic respiration : Incomplete breakdown of organic food to liberate energy in the absence of oxygen.
¶ ATP Synthetase: An enzyme complex that catalysis 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 receive electrrons produced during oxidation-reduction reactions.
Electron trnasport: Movement of electron from substrate to oxygen through respiratory chain during respiration.
¶ Fermentation : Breakdown of organic substance that takes place in certain microbe like yeast under anaerobic condition with the production of CO, and ethanol.
¶ Glycolysis: 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.
¶ Respriation : Biochemical oxidation food to release energy.
¶ Respiratory Quotient: The ratio of the volume of CO2 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 which pyruvic acid undergoes aerobic oxidation through Kreb's cycle.
¶ Electron Transport Chains: (ETC) A series of co- enzymes and electron/ carries where electrons can pass along increasing redox potential losing a bit of energy at every step of transfer.
ATP - Abbreviations
ADP - Adenosine tri phosphate
NAD - Adenosne di phosphate
NADP - Nicotinamide Adenine dinucleotide Phosphate
NADH - Phosphoglyceric acid
PGAL - Phospho glyceraldehyde
FAD - Flavin adenine dinucleotide
ETS - Electron transport system
ETC - Electron transport chain
TAC - Tricarboxylic acid (Cycle)
OAA - Oxalo acetic acid
FMN - Flavin mono nucleotide
PPP - Pentose phosphate pathway
Cellular Rispiration: The process of oxidation/breakdown of food materials within the cell to release energy. Respiratory substarate to be oxidized during respiration is usually glucose, but these can also be proteins, fats or organic acids. In plants respiration gas exchange occurs through stomata and lenticels: Overall cellular respiration is:
C6H₁₂O6 +60₂→6CO₂ + 6H₂O + Energy (36ATPs)
AEROBIC RESPIRATION:
Overall mechanism of aerobic respiration can be studied under the following steps:
(A) Glycolysis (EMP pathway) in cytoplasm
(B) Oxidative Decarboxylation (Gateway Reaction) in Mitochondrial matrix
(C) Kreb's cycle (TCA-cycle)-Matrix of mitochondria
(D) Oxidative phosphorylation
A. Glycolysis: The term has origianted from the Greek word, glycos glucose, lysis - splitting, or breakdown means breakdown of glucose molecule to pyruvic acid. It was given by Embden Meyerhof and Parmas. It is a chainof 10 reactions to convert glucose into pyruvate. It is common for acerobic and anaerdomic respiration.
STEPS FOR GLYCOLYSIS (EMP PATHWAY):
1. Phosphorylation of glucose
2. Formation of fructose 6-phosphate
3, Second phosphorylation
4. Lysis (splitting)
5. Isomerisation of DiHAP
6. Oxidation
7. Substrate Level ATP synthesis
8. Isomerisation or Rearrangement
9. Dehydration
10. Substrate Level ATP Synthesis and formation of Pyruvate.
¶ It is also called Embden-Meyerhof-Paranas pathway. (EMP pathway)
¶ It is common in both aerobic and anaerobic respiration. ¶ It takes palce outside the mitochondria, in the cytoplasm.
¶ One molecule of glucose (Hexose sugar) ultimately produces two molecules of pyruvic acid through glycolysis," .
¶ During this process 4 molecules of ATP are produced while 2 molecules ATP are utilised. Thus net gain of ATP is of 2 molecules.
Net out put..............2 Pyruvate + 2ATP+ 2NADH (+H^+) OR 2 Pyruvate +8 ATP
The pyruvate, so produced, may under go (i) Lactic acid fermentation, Alcoholic fermentation of Aerobic Respiration (Krebs Cycle)
B. Oxidative decarboxylation: Pyruvic acid is converted into Acetyle CoA in presence of pyruvate dehydrogenase complex.
Pyruvic acid+CoA+NAD in the presence of mg^2+ and pyruvate dehydrogenase changes into Acetyle CoA+CO₂+ NADH+H+
C. Tri Carboxylic Acid Cycle (Kereb's cycle) or Citric acid Cycle: This cycle starts with condensation of acetyle group with oxaloacitic acid and water to yield citric acid which under goes a series of reactions.
¶ It is aerobic and takes a place in mitochondrial matrix.
¶ Each pyruvic acid molecule produces 4 NADH + H+, one FADH2,, one ATP.
¶ One glucose molecule has been broken down to release CO2 and eight molecules of NADH+H+, two molecules of FADH2, and 2 molecules of ATP.
Compensation Point: It is the value of a factor at which the rate of photosynthesis controlled by it is just equal to the rate of respiration and photorespiration so that there is not net exchcange of gases between the phtosynthetic organ and the environment. At compensation point the photosynthetic tissue manufacture only such amount of food which of sufficient for it to remain alive. No food is supplied to rest of the plant. Therefore,net photosynthesis is zero.
(D) Oxidative Phosphorylation The synthesis of ATP from ADP and inorganic phosphate using energy from proton gradient is called oxidative phosphorylation. This takes place in elementry particles present on the inner membrane of cristae of mitochondria. This process in mitochondria is catalysed by ATP synthestase (complex V). This compmlex has two major components F0, and and F1, F0 acts a channel for proton and F1 acts as an ATP synthetase.
ELECTRON TRANSPORT SYSTEM AND OXIDATIVE PHOSPHORYLATION:
RESPIRATORY BALANCE SHEET:
glucose +60₂, +36ADP+ 36Pi→ 6CO₂ + 6H₂O +36 ATP
Total ATP Production.
1. Glycolysis → 2ATP +2NADH₂ (6ATP) = 8ATP
2. Oxidative decarboxylation → 2NADH₂ (6ATP) = 6ATP
3. Kreb's Cycle → 2GTP (2ATP) + 6NADH₂ (18ATP) + 2FADH₂ (4ATP) = 24 ATP
Energy production in prokaryotes during aerobic respiration=38 ATP Energy poroduction in eukaryotes during aerobic respiration=38-2=36 ATP.
In eukaryotes 2 ATP are used in transporting 2 molucules of NADH+H formed in glycolysis from cytoplasm to mitochandria for oxidation through ETS shuttle.
(2) Anaerobic Rispiration: In anaerobic respiration, Glycolysis is followed by formation of Ethylacl ohol, lactic acid in the cytoplasm.
Fermentation : It is the process of anaerobic respiration which occurs in yeast and some bacteria. Fermentation involves incomplete oxidation of food into enthanol and carbon-dio-oxide. It results in the production of 2 ATP molcules.
(ii) Synthesis of chlorophyll and cytochromes from Succinyl CoA
(iii) Synthesis of Amino acids from OAA and aketoglutase acid
(iv) Synthesis of Alkaloid from OAA. Enzymes involved-Pyruvic acid decarboxylase, Alcohol dehydrogenase.
Anaerobic respiration in musices: During vigrous exercise a person feels pain and fatigue in his muscles. This is due to accumulation of lactic acid in muscles. When oxygen inadequate pyruvic acid is reduced to lactic acid in presence of enzyne-lactic dehydrogenase.
AMPHIBOLIC PATHWAY:
During the process of cellular respiration Carbohydrates, fats and protiens are broken down to release energy and hence respiration is a catabolic process/ catabolic pathway. From this pathway many compund are wit hdarw for synthesis of substrates. Some anabolic prcesses are repiratory pathway is involved in both catabolism and anabolism, it is better to consider the respiratory pathway as an amphibalic pathway.
RQ (RESPIRATORY QUOTIENT):
(a) RQ = 1 (When carbohydrate is used as substrate) C6H₁₂O6 +60₂6CO₂ + 6 H₂O + Energy
(b) RQ is less than 1 (i.e., < 1) for fats. 2C51H98O6 + 1450₂ →102CO₂ +98 H₂O + Energy
R.Q= 102CO2/145O2 =0.7
(c) RQ is 0.9 for proteins.
(d) RQ is more than 1 (i.e., > 1) for organic acids.
(e) RQ is inifinite in case of anerobic respiration, because CO₂ is evolved but O₂ is not consumed.
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