Respiration in Plants

2. • The energy required for life process is
obtained by oxidation.
• Only green plants and cyanobacteria can
prepare their own food.
• They trap light energy convert chemical energy
• Chemical energy is stored in the bonds of
carbohydrates like glucose, sucrose, starch.
• Only cells containing chloroplast carry out
photosynthesis.

3.  Animals are heterotrophic.
 They obtain food from animals directly or indirectly.
 Saprophytes like fungi are dependent on dead and
decaying matter.
 Respiration taking place in all types of living cell are
called cellular respiration.
 Or, it is the mechanism of breakdown of food
materials within the cell to release energy, and the
trapping of this energy for synthesis of ATP.

4.  The breaking of the C-C bonds of complex compounds
through oxidation within the cells, leading to release
of considerable amount of energy is called Respiration.
 The compounds that are oxidised during this process
are known as Respiratory Substrates.
 They may be carbohydrates, fats and proteins.

5.  During respiration all the energy contained in
respiratory substrate is released in a slow step wise
reactions controlled by enzymes and it is trapped as
chemical energy in the form of ATP.
 This energy trapped in ATP is utilised in various
energy requiring process of organisms.
 The carbon skeleton produced during the respiration
is used as precursors for biosynthesis of other
molecules in the cell.

6.  Plants have stomata and lenticels for
gaseous exchange.
 There are several reasons why plants
can get along without respiratory organs.
 First, each plant part take care of its own gas exchange
needs.
 Second, plants do not present great demands for
exchange. Only during photosynthesis are large
volumes of gases exchanged and each leaf is well
adapted to take care of its own needs.

7.  Third, the distance that gas must diffuse even in large
bulky plant is not great.
 During the process of respiration complete
combustion of glucose with the help of oxygen
produces CO2 and H2O as end products, yields energy
most of which is given out as heat.
 C6H12 O6 + 6O2 6CO2 + 6H2O + Energy

8.  It is originated from the Greek words, glycos for sugar,
and lysis for splitting.
 The scheme of glycolysis was discovered by 3 German
Scientists, Gustav Embden, Otto Meyerhof and J.
Parnas, and therefore, reffered as EMP Pathway .
 Glycolysis is common to both aerobic and anaerobic
modes of respiration
 This is the only process in respiration in anaerobic
organisms.
 Glycolysis occurs in cytoplasm of cells.

9.  1.Phosphorylation of sugar: Glucose and fructose are
phosphorylated to give rise to glucose-6-phosphate and
fructose-6-phosphate respectively, by the activity of
enzyme hexokinase, in the presence of ATP.
 Glucose (6 C) + ATP Mg2+hexokinase Glucose-6-phosphate+ADP
 Now isomerisation occurs:
 Glucose-6-phosphate Fructose-6-phosphate

10.  2.Phosphorylation of fructose-6-phosphate:It is
phosphorylated and fructose-1, 6-bisphosphate by the
action of enzyme phosphofructokinase in pressence of
ATP.
 Fructose-6-phosphate + ATP phosphofrucktokinasemg2+
Fructose-1, 6-biphosphate + ADP
 3.Splitting:
Fructose-1, 6-biphosphate aldolase
3-phosphoglyceraldehyde(PGAL) + dihydroxyacetone
phosphate (Di HAP)

11.  4.Oxidative dehydrogenation:
PGAL + NAD dehydrogenase
glyceraldehyde phosphate
1,3-
bisphosphoglycerate +NADH + H+
 5.Formation of ATP:
1,3-bisphosphoglycerate + ADP phosphoglycerate kinase 3-
phosphoglycerate +ATP
6.Isomerisation:
3-phosphoglycerate 2-phosphoglycerate

12.  7.Dehydration:
2-phosphoglycerate
phosphoenol pyruate+ATP
2-phosphoenol pyruate
pyruvic acid + 2 ATP

13. Main step of EMP pathway

14.  It is defined as the anaerobic breakdown of
carbohydrates and other organic compounds into
alcohol, organic acids etc.
 2 types of fermentation are common:
 1. Alcoholic fermentation: in this type, pyruvic acid is
first decarboxylated to acetaldehyde then to ethanol
 C6 H12 O6 + 2 CH 3CH2 OH +2 CO2

15.  2.Lactic acid fermentation: here,pyruvic acid is
converted into lactic acid by enzyme lactic
dehydrogenase.
 C6 H12 O6 2 CH 3CHOH.COOH

16. Pathway of fermentation in yeast

17.  Pyruate is transported from the cytoplasm into the
mitochondria.
 The crucial events in aerobic respiration are:
 The complete oxidation of pyruate by the stepwise
removal of all the hydrogen atoms, leaving 3 molecules
of CO2.
The passing on of the electrons removed as part of the
hydrogen atoms to molecular O2 with simultaneous
synthesis of ATP.

18.  The first process takes place in the matrix of the
mitochondria while the second process is located on
the inner membrane of the mitochondria.
 Pyruvate undergoes oxidative decarboxylation by a
complex set of reactions catalysed by pyruvic dehydr
ogenase.
 Pyruvic acid + CoA + NAD+ Acetyl CoA +CO2 +
NADH + H+
during this process, 2 molecules of NADH are
produced from the metabolism of 2 molecules of
pyruvic acid.

19.  Sir Hans Adolf Krebs in 1937 discovered tricarboxylic
acid or citric acid cycle or Krebs cycle.
 It occurs in the matrix of mitochondria.
 The starting point of Krebs cycle is entrance of acetyl
CoA into a reaction to form citric acid.

20.  Acetyl CoA + oxaloacetic citric acid + CoA
 Citric acid Cis-aconitic acid +H2 O
 Cis-aconitic acid+H2 O Isocitric acid
 Iso-citric acid + NAD+ Oxalosuccinic acid
+NADH +H+
 Oxalosuccinic acid -Ketoglutaric acid + CO2
 -Ketaglutaric acid + CoA +NAD+ Succinyl CoA +
NADH +H+ +CO2
 Succinyl CoA +H2 O +GDP+ Ip Succinic acid + CoA
+ GTP

21.  GTP+ ADP GDP+ ATP
 Succinic acid + FAD Fumaric acid+ FADH2
 Fumeric acid + H2 O Malic acid
 Malic acid +NAD+ Oxaloacetic acid
 +NADH+H+
 Pyruvic acid +4NAD+ +FAD + 2H2 O+ADP+Ip
 mitochondrial matrix
 3CO2 + 4NADH +H+ +FADH2 +ATP

23.  The metabolic pathway through which electron
passes from one carrier to another is called electron
transport system.
 It is present in the inner mitochondrial membrane.

24.  COMPLEX 1:Electrons to produced are oxidised by an
NADH dehydrogenase and electrons are transferred to
ubiquinone located within the inner membrane.
 COMPLEX 2: Ubiquinone also recieves reducing
equivalents via FADH2 that is generated during
oxidation of succinate in the citric acid cycle.
 COMPLEX 3: The reduced ubiquinone is hen oxidised
with the transfer of electrons to cytochrome c via
cytochrome bc1 .

25.  COMPLEX 4:Cytochrome c oxidase complex
containing cytochromes a and a3 and 2 copper centres.
 Complex 5: When the electrons pass from complex 1 to
4, they are coupled to ATP synthase for the production
of ATP fro ADP.

27. RESPIRATORY QUOTIENT
 It is the ratio of the volume of CO2
evolved to the
volume of O2 consumed in respiration
 RQ =volume of CO2 evolved
 volume of O2 consumed