Definition • Photosynthesis is a process by which cells capture the energy of the sun and store it as chemical energy in complex organic molecules. • During photosynthesis plants make use of carbon dioxide from air, water from the soil, and convert it into glucose in the presence of sunlight.
Overall equation of Photosynthesis • Overall equation
Interconnection between photosynthesis and Cellular respiration
Important Facts • The upper and lower surface of the leaf contains a layer of epidermis. • The outer layers of both epidermal layers is covered by the cuticle, a waxy waterproof covering that reduces the evaporation of water from the leaf. • A leaf obtains carbon dioxide from the air through pores in the epidermis called stomata.
Section of the leaf • Layers of cells between the two layers of epidermis is known as mesophyll. These cells contain chloroplasts, and as a result photosynthesis occurs principally in these cells. • Vascular bundles, or veins, supply water and minerals to the mesophyll cells and carry the sugars they produce to other parts of the plant.
Structure of Chloroplast • Chlorplasts are organelles that consist of a double outer membrane enclosing semi fluid medium, the stroma. • Embedded in the stroma are disk-shaped, interconnected membranous sac called thylakoids. • In most chloroplasts, the thylakoids are piled in stacks called grana. • Grana are connected by stroma lamellae.
Photosynthesis • The chemical reactions of photosynthesis that depend on light (light-dependent reactions) occur within the membranes of the thylakoids. • The photosynthetic reactions that can continue for a time in darkness (light-independent reactions) occur in the stroma.
Photosynthesis Song http://youtu.be/C1_uez5WX1o
Test for Starch • http://www.footprints-science.co.uk/Starch.htm
Which wavelength of light is most effective in driving photosynthesis?Read more:
Action Spectrum • Light at the blue end of the spectrum contains more energy than light at the red end (though red light is more efficiently absorbed than blue). • UV radiation is higher-energy still, but cannot be used. In fact, it causes cell damage and mutations. • Chlorophyll is the most important of all photosynthetic pigment
Action Spectrum Range of wavelength of light that can be used in the light-dependent reaction
Light Dependent Reactions • Chlorophyll and other molecules embedded in the membranes of the thylakoids capture sunlight energy and convert some of them into chemical energy stored in energy-carrier molecules (ATP and NADPH). Oxygen gas is released as a by-product
Light-independent Reactions • Enzymes in the stroma use the chemical energy of the carrier molecules to synthesize glucose or other organic molecules.