Photosynthesis Song!

6.11 The Mechanism of Photosynthesis

Text Book page 133

Watch chloroplast in 3D!

Watch chloroplast in 2D!

Structure of a chloroplastStarch granuleStorage of insoluble products of photosynthesis

Chloroplast envelopePermeable to glucose, ions, O2 and CO2

Thylakoid

Granum•Stacks of thylakoid membrane•Important in ATP synthesis•Site of light reaction

Stroma•Is a gel-like matrix•Site of dark reaction

Lipid droplet

Light Reaction In Granum

Photolysis of water

water

24OH-

24e- 24OH

6O212H2O

chlorophyll24e-24H

24H+

24H2O

Sunlight

Dark reaction in stroma

1. Chlorophyll absorbs sunlight and produces energy. Energy activates the water molecules to dissociate into H+, OH- and e-

Neutral hydroxyl groups combine together to form water and O2

2. Chlorophyll becomes excited and releases e-

3. Each H+ receives an e- from the chlorophyll and is neutralised to form a neutral hydrogen atom (H)

Quick check!

Dark Reaction in Stroma

6CO2

6(CH2O) +

C6H12O6

Starch

6H2O

Released to atmosphere

(Glucose)

4. Hydrogen atoms (H) are used in dark reaction to fix CO2 which is catalysed by photosynthetic enzymes.

6 units of CH2O will combine to form a molecule of glucose.

condensation

Protein Lipids

Quick check!

SPM Clone Question!

Light reaction

Light reaction

R

Q

Light energy

glucose water+

What do P, Q and R represent?

Answer:P = Hydrogen atomQ = oxygenR = carbon dioxide

P

Water + Carbon dioxide Glucose + Oxygen

6H2O 6CO2

Light

Chlorophyll C6H12O6 6O2

SPM Clone Question!

Carbon dioxide + X Glucose Y+

What are X and Y?

Answer: X = water , Y = oxygen

SCHEMATIC DIAGRAM OF PHOTOSYNTHESIS

Photosynthesis

Light Reaction Dark Reaction

Chlorophyll sunlight

Water (H2O)

Hydrogen ions (H+)

CO2Hydrogen (H)

Hydroxide ions (OH-)

Hydroxyl groups (OH)

O2 H2O

Basic glucose units (CH2O)Water (H2O)

Glucose (C6H12O6)

Air / Atmosphere Proteins Lipids Carbohydrates

requires

absorb

Breaks up

combines

forms

Absorb e-

split

Release e-

goes

Comparison between light and dark reactions

Similarities

Differences

As to conclude, watch this!

As to conclude, do this!

1. Define photosynthesis. (2 m)

2. Photosynthesis occurs as a string of chemical reactions. Explain how photosynthesis happens in green plants. (8 m)

Thank you for your attention!

Hehehehe….