Respiration in plants

 Respiration is a catabolic process.

 Respiration is a process by which all plant breaks food
stored food (starch) in presence of O2 and enzyme to
form energy in the form of ATP and CO2 is evolved.

 In cyanobactetia and micrbes small amount of energy is

release in absence of O2.
 Types of respiration

Aerobic respiration Anaerobic respiration

 Takes place in presence of  Takes place in absence of
oxygen oxygen
 Occurs cytoplasm and  Occurs only in cytoplast.
mitochondria.
 In this process incomplete
 In this process complete oxidation of food takes place
oxidation of food takes place.  2 ATP are formed.
 38 ATP energy are formed.  Found in yeast , bacteria and
 Found in Plants and animals human muscles
Aerobic respiration
1. Breakdown of starch
starch ------ maltose -------- Glucose
2. Glycolysis ( breakdown of glucose)
 Also known as emp pathway
 In this step one glucose partially oxidised into two molecule of pyruvic acid.
 It is a 10 step process and each step catalyzed by enzymes.
 Occurs inside the cytoplasm.
 Common pathway found in both aerobic and anaerobic .
 In this process 2 ATP and 2 NADH2 are formed.
Oxidative decarboxylation of pyruvate
to acetyl co – A
 Pyruvic acid is generated in glycolysis enter into the mitochondrial
matrix.
 In mitochondrial matrix oxidative deccur bogulation takes place
 In this step the reaction catalysed by enzyme pyruvate
dehydrogenase.
 Pyruvate dehydrogenase is a enzyme complex
1. Coenzyme ( NAD+)
2. Coenzyme A
3. TPP ( thiamine pyrophosphate )
4. Lipoic acid
5. Mg +2
 Oxytocarboxylation connect glycolysis to krebs cycle.
 Acetyl co A enter into krebs cycle .

 Krebs cycle Or TCA cycle

 It occurs inside the mitochondria in presence of oxygen

 Discovered by Sir Hans krebs

 This is also known as citric acid cycle ( because 1 st stable product is citric acid )
 Also known as tricarboxylic acid cycle (because three carboxylic acid are present in first
stable product)
 First enzyme used – citrate synthes for making citric acid from OAA.
 Step –
 4- 2 NADH2
 6 – 2 NADH2
 10 – 2 NADH2
 7 – 2 GTP
 8 – FADH2

 Mechanism –
 1. Condensation
 OAA + Acetyl Co A + H2O ------------ citric acid + Co A

 2. Isomerisation
 Citric acid --------------------- Cis aconitic acid + H2O
 3. Cis aconitic acid + H2O ---------------- Isocitroc acid

 4. Isocitroc acid + NAD + ------------------- Oxaloacetic acid + NADH2

 5. Decarboxylation
 Oxalosuccinic acid --------------------- alfa ketoglutaric acid + CO2

 6. Decarboxylation
 Alfa ketoglutaric acid + NAD + ------------------- Succinyl Co A + NADH2 + CO2

 7. Succinyl Co A + GDP ------------------ Succinate + GTP

 8. Succinate + FAD+ ---------------- Fumeric acid + FADH2

 9. Fumaric acid. -------------------- Malic acid

 10. Malic acid. ……………………. OAA

 Electron transport system & oxidative phosphorylation
 Election transport chain is a series of co-enzyme and Cytochrome
located in the inner mitochondriad membrane
 In this process ATP production takes place through the e-
transport.
 In this process H+ ion and e- are produced in the matrix.
 There e- and H+ion are acccepted by two H acceptor Co-enzymes.
i.e NAD and FAD
 Both acceptor of H+ ion and e- gets reduce in original form and
release H+ and e – into the membrane of mitochondria.
 The H+ and e - passed down through the complexes of e- transport
chain
 Following 4 complexes consist to the e - transport System.
 Complex 1.enzyme- NADH dehydrogenase
 Complex 2.Succinic dehydrogenase
 Complex 3.enzyme - Cytochrom b+ Cytochrome C1
 Complex 4.enzyme- lytochrome a and a3

 In ETS the following two types of mobile electron

transport carrier are -
 Ubiquinone
 Cytochrome C
 Mechanism
 Electron from NADH produced in the mitochondrial matrix during citric acid
cycle are oxidised by an NADH dehydrogenase (complex I).
 Electrons are then transferred from oxidised NADH to ubiquinone located
within the inner membrane.
 Ubiquinone also receives reducing equivalents via FADH, (complex II) that is
generated during oxidation of succinate in the citric acid cycle.
 The reduced ubiquinone (ubiquinol) is then oxidised with the transfer of
electrons to cytochrome c via cytochrome bc₁ complex (complex III).
 Cytochrome c is a small protein attached to the outer surface of the inner
membrane and acts as a mobile carrier for transfer of electrons between
complex III and IV.
 Complex IV refers to cytochrome c oxidase complex containing cytochromes
a a and a1 and two copper centres.
 When the electrons pass from one carrier to another via complex I to IV in
the electron transport chain, they are coupled to ATP synthase (complex V)
for the production of ATP from ADP and inorganic phosphate.
 The number of ATP molecules synthesised depends on the nature of the
electron donor.
1.Oxidation of one molecule of NADH gives rise to 3 molecules of ATP,
2. while that of one molecule of FADH, produces 2 molecules of ATP.
 Although the aerobic process of respiration takes place only in the presence
of oxygen.
 The role of oxygen is limited to the terminal stage of the process.
 Oxygen (Viral ) acts as the final hydrogen acceptor.
Oxidative phosphorylation

 In respiration the energy of oxidation-reduction utilised for the

ATP production.
 It is for this reason that the process is called oxidative
phosphorylation.
 Energy released in transport system is utilised in synthesising ATP
with the help of ATP synthase (complex V).
 This complex consists of two major components (F0 and F1)
 The F1 headpiece is a peripheral membrane protein complex and
contains the site for synthesis of ATP from ADP and inorganic
phosphate.
 Fo is an integral membrane protein complex that forms the channel
through which protons cross the inner membrane.
 The passage of protons through the channel is coupled to the catalytic
site of the F1 component for the production of ATP.
 For each ATP produced, 4H passes through F1 from the intermembrane
space to the matrix down the electrochemical proton gradient.
Anaerobic respiration ( fermenation )
 Fermentation is a biochemical process that breaks down complex
sugars into smaller molecules, releasing energy and gases in absence
of oxygen.
 Types of fermentation
1. Alcoholic fermentation
2. Lactate fermentation
. 1. Alcoholic fermentation -
 It takes place inside the yeast ,bacteria and fungi.
 Occurs in absence of oxygen
 Enzyme involved
pyruvate decarboxylase & Alcohol dihydrogenase
 It is used for the prepareing beverage like rum whisky brandy etc
Q

2. Decarboxylation
Pyruvic acid --------------------- Acetaldehyde + CO2

3. Reduction of ethanol

Acetaldehyde + NADH +H ----------------- Ethanol

On above reaction one glucose molecule produces two molecular ethyl

alcohol.
Lactic acid fermentation

 It takes place inside the lactic acid bacteria skeleton muscles and fungi
 Occurs in absence of oxygen
 Enzyme involved Lactate dihydrogenase
1. Glycolysis NAD – NADH2
Glucose ---------- G3P -------------3 PGA ---------PEP ----------Pyruvic acid

Pyruvic acid NADH+ H ----------------- Lactic acid + NAD +

Amphibolic Pathway

 An amphibolic pathway is a biochemical pathway that combines

both anabolic and catabolic processes.
 The term was coined by B. Davis in 1961.
 When energy is required, proteins or fatty acids are broken
down to form acetyl-CoA and further processes of respiration
occur. This is catabolism.
 When the body requires fatty acids or proteins, respiratory
pathway stops and the same acetyl-CoA is utilized and fatty
acids are manufactured. This process of synthesis is termed
as anabolism.
 Thus we can say respiration is the sum process of catabolism
and anabolism.
Respiratory quotient RQ
 Respiratory Quotient (RQ )=Volume of CO2 / Volume of O2
 Respiratory Quotient – the ratio of volume of co2 produced to the
volume of O2 consume over a specific period by tissue it is called RQ
value.
 RQ of Cb = 1

 RQ of fat = 0.7

 RQ of protein = 0.9
 RQ of organic acid (Oxalic acid ) = 4
 RQ of Opuntia = 0
 RQ of anaerobic respiration = infinite