What are the process occurs in photosynthesis?

How starch is synthesize?

THYLAKOID

ChloroplastDark reaction occurs

Light reaction occurs

STROMA

Light Reactiono Light energy Chemical energyo Chlorophyll & accessory pigments absorb

slightly different color of light and pass its energy to central chlorophyll molecule (Chlorophyll a) to do photosynthesis.

o Two forms of chlorophyll a molecules(a)P700 in PSI (700 nm)(b)P680 in PSII(680 nm)o Role of Photosystem:Provide sufficient energy to boost the

photoactivated electron to an energy level high enough accepted by NADP

: pump proton across thylakoid membranes.

Non-cyclic photophosphorylation

Cyclic Photophosphorylation

Photosynthesis: Pathway of Carbon Fixation

STARCH

CO2 combines with the phosphorylated 5-carbon sugar ribulose bisphosphate (RUBP)

reaction is catalyzed by the enzyme ribulose bisphosphate carboxylase oxygenase (RUBISCO)

resulting 6-carbon compound breaks down into two molecules of 3-phosphoglyceric acid (PGA).

PGA molecules are further phosphorylated (by ATP) and are reduced (by NADPH) to form phosphoglyceraldehyde (PGAL).

Enzyme responsible for fixing 200 bilion

tons of CO2 anually

Phosphoglyceraldehyde (PGAL) serves as the starting material for the synthesis of glucose and fructose.

Glucose and fructose

PolysaccharideSynthesis starch & cellulose

Travel to other part of the plant

As Monomer

Sucrose

CARBOXYLATION

REDUCTION

REGENERATION

CO2 + H20

3-phosphoglycerate

ATP + NADPH

ADP + Pi NADP+

Triose PhosphateSucrose, Starch

ATP

ADP

Equation of sugar glucose

6CO2 + 12H2O C6H12O6 + 6H2O + 6O2

CH2O~PChlorophyll

H20

O2

CH2O~P

H20

CO2 + H2O

(CH2O)n

ATP

[ADP + Pi], NADP+

+ NADPH

Light

Reduction Processin Calvin cycle

• Adds a phosphate from ATP to the 3-PGA • removes hydrogen from NADPH and adds it

to the 1,3-bisphosphoglycerate • In this reduction, a phosphate is removed • resulting NADP+, ADP, and Pi can be recycled

to the light reactions • These steps demonstrate why the light

reactions and Calvin cycle are interdependent

Why convert Glucose to Starch?

• products of photosynthesis are assembled in plant to make glucose

• Glucose (C6H12O6) is a monosaccharide or single sugar

• plant uses glucose as short-term energy storage • converted into a polysaccharide called starch,

allowing the plant to store most of the energy collected in photosynthesis in the chemical bonds between the sugars

• When the plant needs energy, the bonds holding the glucose molecules together are broken, and energy is released

• Starch is a better way to store energy because it has more bonds to hold potential energy and it can be stored in large amounts without disturbing the rest of the plant.