sharing one of the most beautiful creations of allah

8/14/2019 Sharing One of the Most Beautiful Creations of Allah

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SHARING ONE OF THE MOST BEAUTIFUL CREATIONS OF ALLAH

PHOTOSYNTHESIS


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BRIEF HISTORY OF

PHOTOSYNTHESIS

1640: Jean Baptiste van Helmont studythe growth of plants. (plants grew mainlyfrom water not soil)

1772: Joseph Priestley green plantsrestore oxygen which can supportcombustion (candle in an upturned glass

jar) Jan Ingenhousz: Plants only releaseoxygen in the presence of sunlight


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BRIEF HISTORY OF

PHOTOSYNTHESIS

1780s: Jean Senebier carbon dioxide was

taken by plants during photosynthesis.

1796: Ingenhousz verified that carbon dioxide is

the source of carbon for photosynthesis 1804: de Saussure water required for

photosynthesis

1845: Robert Mayer plants convert photoenergy into chemical energy during

photosynthesis.


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BRIEF HISTORY OF

PHOTOSYNTHESIS

1905: Blackman photosynthesis involves2 principal reactions (photochemical andbiochemical). Photochemical is light-

dependent, biochemical is light-independent

1937: Robert Hill chloroplasts are able toproduce oxygen by splitting watermolecules in the absence of carbondioxide.


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LEAF STRUCTURE & FUNCTION


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CROSS SECTION OF LEAF


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LEAF STRUCTURE & FUNCTION

Xylem: transports water

Phloem: transports organic products ofphotosynthesis

Epidermis: protective layer on the upper andlower surfaces of the leaf

Cuticle: waterproof layer which reduce excessivewater lost

Stomata: allowing exchange of gases betweenthe internal part of the leaf and the environment

Guard cells: regulate the size of the pore.


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STRUCTURE OF CHLOROPLAST


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PHOTOSYNTHESIS LIGHT

REACTION

Takes place in the grana

The raw material needed is water

During light reaction, chlorophyll captureslight energy which excites the electrons of

chlorophyll molecules

Light energy is also used to split watermolecules into hydrogen ions (H+) and

hydroxyl ions (OH-): PHOTOLYSIS


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REACTION

The hydrogen ions then combine with the

electrons released by chlorophyll to form

hydrogen atoms.

Energy released from the excited electrons isused to form energy rich molecules of ATP

At the same time, each hydroxyl ion loses an

electron to form hydroxyl group. Hydroxyl groups

combine to form water and gaseous oxygen.

Oxygen is released into atmosphere


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REACTION

24H2O 24H+ + 24OH-

24H+

+ 24e-

24 H (hydrogen atoms)

24 OH- 24OH + 24 e-

24 OH 12H2O + 6O2

LIGHT

CHLOROPYLL


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PHOTOSYNTHESIS DARK

REACTION

The ATP molecules and hydrogen atoms

move to the stroma to provide energy

Hydrogen atoms are used to fix carbon

dioxide in a series of reactions catalysed

by photosynthetic enzymes.

Overall reaction results in the reduction of

carbon dioxide into glucose.


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PHOTOSYNTHESIS DARK

REACTION

6CO2 + 24H 6(CH2O) + 6 H2O 6 (CH2O) C6H12O6


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PHOTOSYNTHESIS

Glucose monomers then undergo

condensation to form starch which is

temporarily stored as starch granules in

the chloroplasts.

The entire process of photosynthesis can

be represented by the following chemical

equation: 12H2O + 6CO2 C6H12O6 + 6O2 +6H2O

LIGHT

CHLOROPYLL


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EVALUATION

Work in groups. Review the mechanism ofphotosynthesis which has been discussed and list out

the comparison between light and dark reaction.

Dark ReactionDifferencesLight Reaction

Light energy

required

Site of reaction

Substancesrequired for

reaction

Products of

reaction

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