PHOTOSYNTHESIS…

Presented ByMajid Mushtaq Kichloo.Lecturer DIET kishtwar.

Jammu & kashmir (india)

INTRODUCTION.

.

( LIGHT ) ( PUTTING TOGETHER )

It’s the most important ANABOLIC process on earth by which AUTOTROPHS synthesizes the complex

carbohydrates from simpler substances' like Carbon dioxide,water,sunlight with the

help of Chlorophyll & purify the atmospheric air by consuming carbon

dioxide & water & in turn evolve oxygen.

(OR)

It can also be defined as the transfer of photonic energy i.e. light or radiant energy into chemical energy which is locked in high energy bonds of carbohydrates molecules by green parts of the plants.

(OR)

Each day the radiant energy that reaches to thesurface of earth is equal to 1 millionHIROSHIMA SIZED ATOMIC BOMBS.

Photosynthesis capturer about 01 percent ofthe huge supply of energy which is equal to10,000 (ten thousand) HIROSHIMA BOMBSis used to provide the energy that drives theliving world.

1.7×1017 J total energy from the Sun that

strikes the face of the Earth each second.

EQUATION OF PHOTOSYNTHESIS

The simple over all equation usually represent

Photosynthesis is:-

6CO + 6H O C H O + 6H O

This equation represents the early modal of photosynthesis when it was presumed that molecular oxygen came from carbon dioxide not from water.

light

Chlorophyll2 2 6 12 6 2

Later on C.B Van Niel (1931) observed that during

bacterial photosynthesis Hydrogen Sulphide H S is

broken down to Hydrogen & Sulphur.The

Hydrogen reduces Carbon dioxide to synthesize

carbohydrates & Sulphur is accumulated as a waste

product.

CO +2 H S (CHO)+HO+2 S (Ist)

6CO +12H S (C H O )+6H O+12 S

2

22

22 2light

Bacterial Chlorophyll

Bact. Chl.

light26126

2

This led to the postulation that in higher plants

water is utilized in place of H S & O is evolved in

place of Sulphur.

10 years latter this hypothesis was confirmed

by isotopic studies made by RUMEN & KAMEN

(1941).They use radioactive isotopes of oxygen

( O ) in water & found that O liberated in this

process comes from H O not from CO .On the

contrary when ( O ) in CO was used the evolved

O did not show radioactivity.

2 2

2

2

218

18 2 2

Thus the over all equation of photosynthesis is currently

accepted as :-

6CO +12H O C H O + 6O + 6HO612622 Chlorophyll

light

2 2

Significances of photosynthesis

1.It is a vital process for life on planet earth. This process consume atmospheric Carbon dioxide & water & yields carbohydrates & Oxygen.

2.Sugars produced during this process are further used by plants to synthesize organic

acids,proteins,fats,phytohormones,

Vitamins, Nucleic acid etc.

3. Solar energy trapped by the green plants meet

the food requirement of all other living

organisms, in addition we used plants for many

purposes like fiber, fire wood, timber etc.

4.Fossil fuels & natural gases are also the

products of photosynthesis.

5.It provides food indirectly as meat, milk etc.

6.It is the process which maintain the delicate

balance of carbon dioxide & oxygen in the

atmosphere.

• The plants absorb water and minerals from the soil by means of roots.

• The Transpiration Pull Theory -

1. Cohesion

2. Tension

Water :-it is one of the important reactant of photosynthesis, it is absorbed from soil with the help of roots by the process of osmosis it is also essential for opening & closing of stomata for gaseous exchange. it supplies the electron for reduction of NADP,the oxygen evolved during photosynthesis comes from water by the process of photolysis. Plants supplied with less water have low rate of photosynthesis. The translocation of minerals, food etc. takes place with the help of water. Thus it is one of the important raw material for photosynthesis.

The exchange of gases takes place in stomata, in leaves & in lenticels, in the bark of trees through the process of diffusion.

Carbon dioxide:-

it is also one of the important reactant of

photosynthesis, which is absorbed from the

surroundings through stomata by the

process of diffusion. it is used during dark

reaction of photosynthesis to prepare

carbohydrates.

Leaf Structure• Most photosynthesis occurs in the palisade layer.• Gas exchange of CO2 and O2 occurs at openings called

stomata surrounded by guard cells on the lower leaf surface.

Palisade

Spongy

Chloroplast Structure• Inner membrane

called the thylakoidmembrane.

• Thickened regions called thylakoids. A stack of thylakoids is called a granum. (Plural – grana)

• Stroma is a liquid surrounding the thylakoids.

Types & Distribution of pigmentsPIGMENTS. DISTRIBUTION.

Chlorophyll “a” All photosynthetic organisms except photosynthetic bacteria.

Chlorophyll “b” Chlorophyta,Euglenophyta & all higher plants.

Chlorophyll “c” Brown algae (Pheophyta),Diatoms& Pyrrophyta.

Chlorophyll “d” Red Algae (Rhodophyta)

Chlorophyll “e” Xanthophyta.

BacterioChlorophyll . Purple photosynthetic bacteria.

ChlorobiumChlorophyll.(Bacterioviridin)

Green sulphur bacteria.

Pigments

• Chlorophyll A is the most important photosynthetic pigment.

• Other pigments called antenna or accessory pigments are also present in the leaf.

– Chlorophyll B

– Carotenoids (orange / red)

– Xanthophylls (yellow / brown)

• These pigments are embedded in the membranes of the chloroplast in groups called photosystems.

Light:-

Light supplies the energy in fact it is the basic source

of energy in the living world the sun light consist of

seven different colours chlorophyll can absorb Red,

blue & violet coloured light & reflects green. The

maximum photosynthesis occurs in Red light

followed blue & minimum photosynthesis occurs in

green light .

The quantity, quality and duration of light affects the

rate of photosynthesis.

Light Reactions

• Light-dependent reactions occur on the

thylakoid membranes.

– Light and water are required for this

process.

– Energy storage molecules are formed. (ATP

and NADPH)

– Oxygen gas is made as a waste product.

Dark Reactions

• Dark reactions (light-independent) occur in the

stroma.

– Carbon dioxide is “fixed” into the sugar

glucose.

– ATP and NADPH molecules created during the

light reactions power the production of this

glucose.