2. Respiration - Definition
The energy stored in photosynthetic
products during Photosynthesis is
released by oxidation of that
products into CO2 & H2O
C6H12O6 + 6O2 + 6H2O
6CO2 + 12H2O + Energy (686 K. Calories)
3. SIGNIFICANCE OF RESPIRATION:
Respiration is an important process because
1. It releases energy which is consumed in various metabolic
processes essential for plant life and activates cell division.
2. It brings about the formation of other necessary compounds
participating as important cell constituents.
3. It converts insoluble food into soluble form.
4. It liberates CO2 and plays a part actively in maintaining the
balance of carbon cycle in nature.
5. It converts stored energy (potential energy) into usable form
(kinetic energy)
4. Respiration is of two types
1. Aerobic respiration – in presence of O2
2. Anaerobic respiration – in absence of O2
Aerobic respiration – The process of producing the cellular
energy involving oxygen
5. Anaerobic respiration
1st step- Glucose 2 Pyruvic acid
In Yeasts: 2 PA 2 Ethyl alcohol + CO2
Glycolysis
Fermentation process
2 molecules of ATP released
6. Stages of Respiration
Glycolysis
Link Reaction
Krebs Cycle
Electron Transport System Chain
Oxidative phosphorylation
7. Glycolysis
Greek word- Glykos = ‘sugar’ , lysis = ‘splitting’
Anaerobic process
It is the first step of aerobic respiration
Common step for aerobic and anaerobic respiration
Occur in cytoplasm
Also call EMP pathway (Embden, Meyerhoff, Parnes)
9. Glucose
2 Pyruvic acid
4 ATP
2 ATP
2 NADH
NET GAIN = 2 ATP & 2 NADH
Gross ATP = 8 ATP [1 NADH=3ATP]
Glycolysis
10. Why we get only 2 ATP during anaerobic
breakdown of glucose molecules??
Glucose Ethanol
2 Pyruvate 2 Acetaldehyde
NAD+
NADH
--------------------------------
------------------------------
Alcohol
dehydrogenase
Pyruvate
decarboxylase
G-3P
dehydrogenase
12. The oxidative pentose phosphate pathway plays several roles in plant metabolism:
NADPH is thought to drive reductive steps associated with various biosynthetic reactions
that occur in the cytosol such as lipid biosynthesis and nitrogen assimilation.
Some of the reducing power generated by this pathway may contribute to cellular energy
metabolism
The pathway produces ribose 5 phosphate, a precursor of the ribose and deoxyribose
needed in the synthesis of RNA and DNA respectively.
Another intermediate in this pathway, the four carbon erythrose – 4 - phosphate, combines
with PEP in the initial reaction that produces plant phenolic compounds including the
aromatic amino acids and the precursors of lignin, flavonoids and phytoalexins.
During the early stages of greening, before leaf tissues become fully photoautotrophic, the
oxidative pentose phosphate pathway is thought to be involved in generating Calvin
Cycle intermediates
13. Formation of Acetyl Co A
2 NAD+ 2 NADH
2 Pyruvic acid 2 Acetyl CoA
Coenzyme A
2 CO2
TCA
Cycle
Oxidative Decarboxylation
Link Reaction -
Co-factors:
Magnesium ion
Thiamine pyrophosphate
NAD+
Co-enzyme-A
Lipoic acid
14.
15. Krebs Cycle
• Requires Oxygen (Aerobic)
• Takes place in matrix of mitochondria (Inner membrane)
OAA Citric Acid
Acetyl COA
TCA Cycle
17. Krebs Cycle Summary
For each Glucose molecule, the Krebs
Cycle produces
6 NADH, 2 FADH2 and 2 ATP
1NADH = 3 ATP
1 FADH2 = 2 ATP
3 NADH, 1 FADH2 and 1 ATP
2 kreb cycle
18. Electron Transport Chain
Oxidative Phosphorylation
Four complex proteins involved
NAD
FAD/FMN
Co-enzyme- Q
Cytochromes- b,c,a,a3
Complex I to Complex IV
Electron transport through electron carriers
Oxidation of Coenzymes & energy is released
Energy utilized for phosphorylation
(ADP + Pi ------- ATP) - Phosphorylation By Oxidation called as
Oxidative Phosphorylation
20. Respiration – Net Energy
Pathway NADH FADH ATP TOTAL
ATP
Glycolysis 2 (6) - 2 8
Oxidative
decarboxylation
2 (6) - - 6
Krebs cycle 6 (18) 2 (4) 2 24
Total ATP 30 4 4 38
TOTAL = 36 ATP
21. Oxidative Phosphorylation Photophosphorylation
It occurs during Respiration It occurs during Photosynthesis
Found inside of Mitochondria Found inside of Chloroplast
Process occurs IM of MC Occurs in Thylakoid membrane
Oxygen is needed Oxygen is not required
ETS made up of Cytochromes ETS made up of PS I & PS II
Electron donor is NADH Electron donor is water
Electron acceptor is O2 Electron acceptor is NADP
Produced ATP molecules are used for
different metabolic reactions
Produced ATP molecules are used for
CO2 fixation in dark reaction
22.
23. Total dry matter = Function of canopy photosynthesis and canopy
respiration
Canopy Photosynthesis - Canopy Respiration = Net Photosynthates (G & D)
Canopy respiration = Dark respiration + Photorespiration
Survival of any plant – decided by metabolic activities
Metabolic activity – ATP required
ATP – obtained from oxidation of food materials (carbohydrates, proteins,
lipids).
Food materials – from photosynthesis
So, photosynthetic/respiratory ratio = >1
24. GROWTH AND MAINTENANCE RESPIRATION
GROWTH
Synthesis and accumulation of
material.
Depends only on actual new growth
made by plant.
Denoted as ‘kP’
k= constant
P= rate of photosynthesis
MAINTENANCE
Repair and restoration, operation of all
metabolic systems.
Turnover, transport, maintenance of
gradients of all sorts – for operating
controls and signal system.
Function of plant size
Denoted as ‘cW’
c= constant
W= dry weight of plant
26. RESPIRATORY SUBSTRATES
Respiratory substrate – Any organic plant constituent oxidised partially or
completely in respiratory metabolism
Principal respiratory substrates in cells of higher plants – Carbohydrates
Imp. Respiratory substrates among carbohydrates- Sucrose, Starch
Some other substances as respiratory reserves are:
Castor – Lipid reserve in endosperm
CAM plants – Organic acids
Detached leaves - Proteins
27. RESPIRATORY QUOTIENT (R.Q.)
Substrates RQ
Carbohydrates 1.00
Proteins when ammonia produced in oxidation 0.99
Proteins with amide formation 0.80
Fats 0.70
Organic acids 1.33
(R.Q.) = ---------------------------------
Volume of CO2 evolved
Volume of O2 absorbed
28. ALTERNATE RESPIRATION/ CYANIDE RESISTANT RESPIRATION
CYANIDE – added to actively respiring animal tissues – cyt- c oxidase
inhibited.
Respiration rate – quickly drops to <1% of initial level.
Most plants – cyanide resistant respiration
10-25% in some and in some tissues – 100% uninhibited
Enzyme responsible for O2 uptake – cyanide resistant oxidase (component of
plant mitochondrial ETS called alternate oxidase).
29. SALT RESPIRATION
Roots absorb salt- respiration rate rises.
Rise- energy spent in absorbing salts or ions – the required energy supplied by
increased respiration.
The phenomena – Salt respiration.
Inference – respiration represents increased metabolism – need to generate
energy for active transport of ions.
Relationship- not always linear.
Salt respiration – persists after salts removed.
Hence, no clue to the coupling of respiration and ion transport.
30. WOUND RESPIRATION
Wounding of plant organ – stimulate respiration.
Initiate meristematic activity in region of wound – result in ‘wound callus’.
Wounding increased – sugar content
Increase in respiration – increased availability of respiratory substrate in
wounded tissues.
31. MEASUREMENT OF RESPIRATION
By quantitative determination of CO2 evolved or O2 consumed.
Different methods of measurement of respiration
Weight method
Titration method
Quantitative method
Manometric method
Infrared CO2 analyser or paramagnetic O2 analyser
32. Weight method
* CO2 produced by plant – trapped in barium hydroxide solution.
* Weight of Barium carbonate formed - CO2 produced
Titration method
* CO2 produced – dissolved in NaOH
* Amount of CO2 absorbed – estimated by titration
Quantitative method
* Released CO2 – measured by passing an air stream through sealed chamber
containing plant tissue into alkaline solution
* Changes in ph and E.C recorded.
* Recorded changes - CO2 released by tissue calculated
33. Manometric method
* CO2 release or O2 uptake – measure by manometer.
* Sliced plant samples- suspended in water in a flask.
* Changes in amount of respiratory gases – reflected in change in pressure.
* Changes in pressure- measured by manometer.
Infrared CO2 analyser or paramagnetic O2 analyser
* Instrument measuring changes in CO2 or O2 of atm. and plants in sealed
chambers.
* A membrane bound polarographic electrode sensitive to O2 can measure
changes in the concentration of O2 in a solution