Photosynthesis A naturally occurring biological process Very complex It is an endogenic, anabolic reaction resulting in the production of glucose and oxygen. Carried out by green plants, blue-algae and certain bacteria.

Organisms (autotrophs) are able to harness the energy contained in sunlight through a series of reactions. Resulting in the production of oxygen and sugar and other compounds.

Overall equation for photosynthesis 6 CO2 + 6 H2O C6H12O6 + 6O2 sunlight (radiant energy) Reactants Products

Leaf Structure Chloroplasts are concentrated in the mesophyll of the leaf Tiny pores in the lower epidermis (stomata) allows for CO2 to enter and O2 to exit. Veins carry water and nutrient from the plants roots to the leaves

Organelle where photosynthesis takes place Chloroplast Organelle where photosynthesis takes place Contain chemical compounds called: Chlorophyll

Chloroplast Structure Has inner and outer membranes Inner membrane encloses a thick fluid called STROMA Floating in the stroma are disk-shaped sacs called Thylakoids.(arranged in stacks called GRANA)

Thylakoids The thylakoid is the structural unit of photosynthesis. Both photosynthetic prokaryotes and eukaryotes have these flattened sacs/vesicles containing chlorophyll

The Light Reaction Take place in the thylakoid membranes, convert light energy to the chemical energy of ATP and NADPH. The light reactions use the reactant water from the equation and release the product oxygen.

Calvin Cycle Like a sugar factory within a chloroplast. It is called a cycle because the starting material is regenerated each time the process occurs. The starting material that gets regenerated is a compound called RuBP, a sugar with five carbons

The Calvin cycle Takes place in the stroma Uses ATP and NADPH to convert carbon dioxide to sugar

Reactants and Products With each turn of the Calvin cycle, there are chemical reactants and products. The reactants are carbon dioxide from the air and the ATP and NADPH produced by the light reactions.

Calvin Cycle Reactants The Calvin cycle uses carbon from the carbon dioxide, energy from the ATP, and high-energy electrons and hydrogen ions from the NADPH.

Calvin Cycle Products Is an energy-rich sugar molecule. That sugar is not yet glucose, but a smaller sugar named G3P. The plant cell uses G3P as the raw material to make glucose and other organic molecules it needs.

Summary of Photosynthesis Recall that the overall equation for photosynthesis is: 6 CO2 + 6 H2O C6H12O6 + 6 O2

Flow of Energy By converting light energy to chemical energy, photosynthesis is the first step in the flow of energy through an ecosystem.

Some of that chemical energy then passes from producers to consumers. Even when people eat meat, you can trace its stored energy back to photosynthesis. Photosynthesis is the ultimate source of all the food you eat and all the oxygen you breathe.

The nature of light The energy produced by the sun reaches the earth as electromagnetic radiation. Light and other forms of electromagnetic radiation are considered to have both a wave nature and a particle nature.

Particles or packets of light (its particle nature) are known as photons - the smallest divisible units of light. The distance moved by a photon during one of it vibrations is referred to as its wavelength and is measured in nanometers (nm).

Visible light A very small part of this spectrum can be seen by the human eye i.e. between the wavelengths 400 and 700 nm. This part of the electromagnetic spectrum is called visible light. Almost all life depends ultimately on this part of the spectrum for its energy.

Why plants only use visible light as a source of energy for photosynthesis Each photon of visible light contains just enough energy to excite the electrons of molecules without causing damage to the cell.

Light and photosynthesis Chlorophyll absorbs blue-violet and red-orange Reflects green back Chlorophyll a, the most important light-absorbing pigment in plants, does not absorb light in the green part of the spectrum.  Light in this range of wavelengths is reflected.

Light and photosynthesis Plants do not depend only on chlorophyll a but also have other pigments (accessory pigments) which absorb light of  different wavelengths.