• 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.

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.

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.

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.

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.

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

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.

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+ADPNow isomerisation occurs:Glucose-6-phosphate Fructose-6-

phosphate

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 phosphofrucktokinase

mg2+ Fructose-1, 6-biphosphate + ADP

3.Splitting: Fructose-1, 6-biphosphate aldolase

3-phosphoglyceraldehyde(PGAL) + dihydroxyacetone phosphate (Di HAP)

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 +ATP6.Isomerisation:3-phosphoglycerate 2-

phosphoglycerate

7.Dehydration:2-phosphoglycerate phosphoenol pyruate+ATP2-phosphoenol pyruate pyruvic acid + 2 ATP

Main step of EMP pathway

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

2.Lactic acid fermentation: here,pyruvic acid is converted into lactic acid by enzyme lactic dehydrogenase.

C6 H12 O6 2 CH 3CHOH.COOH

Pathway of fermentation in yeast

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.

AEROBIC RESPIRATION

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.

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.

TRICARBOXYLIC ACID CYCLE

Acetyl CoA + oxaloacetic citric acid + CoA

Citric acid Cis-aconitic acid +H2 O

Cis-aconitic acid+H2 O Isocitric acidIso-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

REACTIONS IN KREBS CYCLE

GTP+ ADP GDP+ ATPSuccinic 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

KREB CYCLE

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.

ELECTRON TRANSPORT SYSTEM

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 .

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.

RESPIRATORY QUOTIENTIt 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

PRESENTED BYDINCY