Photosynthesis

Lauren Dever, Madison DevineLauren Kissel, and Anna Moloney

PHOTOSYNTHESIS

• The conversion of light energy to chemical energy

• Stored in glucose or other organic compounds

• Occurs in plants, algae, and other prokaryotes

PHOTOSYNTHESIS

• Photosynthesis involves the conversion of light energy into chemical energy.

• The process uses light energy and simple inorganic substances such as CO2 and H2O to produce organic compounds

PHOTOSYNTHESIS

• Light from the sun is composed of a range of wavelengths (colors)

• Plants are photoautotrophs, organisms that use light as a source of energy to synthesize organic substances

PHOTOSYNTHESIS

• Pigments that absorb all colors except blue appear blue because his part of the sunlight is not absorbed

• The blue light is reflected and can pass into our eye, to be perceived by cells in the retina

• A white or transparent substance does not absorb visible light

• Pigments that absorb all of the light appear black

PHOTOSYNTHESIS

• Photosynthesis is only able to occur in wavelengths that chlorophyll can absorb

• Shorter wavelengths have more energy, this leads to higher rates of photosynthesis

• Medium wavelengths (green) have the lowest rate of photosynthesis

PHOTOSYNTHESIS

• Chlorophyll is the main photosynthetic pigment• Chlorophyll is the green pigment located within chloroplasts

PHOTOSYNTHESIS

• ATP and hydrogen are used to fix carbon dioxide to make organic molecules

• The conversion of carbon dioxide into solid or liquid carbon compounds is called carbon fixation

PHOTOSYNTHESIS

• The three limiting factors of photosynthesis are light intensity, temperature, and carbon dioxide concentration

• They can all affect the rate at which a plant goes through photosynthesis if they are below the optimal level

• There is only one limiting factor at a time and they change throughout the process of photosynthesis

The Effect of Temperature

The Intensity of Light

The Effect of Carbon Dioxide Concentration

PHOTOSYNTHESIS

• The various structures in the chloroplast are highly visible in this electron micrograph image• This is where photosynthesis occurs

PHOTOSYNTHESIS

• Chloroplasts have such characteristics as– A double membrane called the chloroplast

envelope– A complex system of internal membranes

known as thylakoids– Small spaces of fluid inside the thylakoids– Fluid surrounding the thylakoids known as

stroma

PHOTOSYNTHESIS

• Photosynthesis consists of two different parts of reactions, light- dependent and light- independent

• Light- dependent reactions involve the production of ATP

• Light- independent reactions involve the production of glucose, known as the Calvin cycle

• However, they are a result of the light- dependent reactions so they are indirectly dependent on light

PHOTOSYNTHESIS

• Light energy is used to produce ATP and to split water molecules (photolysis) to form oxygen and hydrogen- The light energy is absorbed by chlorophyll

• Light- dependent reactions produce ATP by means of photophosphorylation

• The light absorbed takes the form of electrons in the thylakoids

PHOTOSYNTHESIS

• The process begins in Photosystem II, it then proceeds to the electron transport carrier, and then to the ATP synthase

• A proton concentration gradient forms in the thylakoid membrane helping to create ATP

• In cell respiration, this is known as chemiosmosis

PHOTOSYNTHESIS

• Photosystem I produces NADPH which is used in the light- independent reactions

• The chlorophyll absorb light and raise one electron to a high energy level, called photoactivation

• The electron is connected to the electron chain from Photosystem II and used to reduce NADP+

• Cyclic photophosphorylation

PHOTOSYNTHESIS

PHOTOSYNTHESIS

• Carbon fixation and carbohydrate synthesis are light- independent reactions, these are known as the Calvin cycle

• Carbon fixation produces glycerate- 3- phosphate, a three- carbon compound

• The carbon dioxide mixes with ribulose biphosphate, a 5- carbon compound to create glycerate- 3- phosphate

PHOTOSYNTHESIS

• For a carbohydrate to be produced, hydrogen has to be added to the glycerate- 3- compound, ATP and NADPH are needed for this to occur

• The result of this reaction is a three- carbon sugar called triose phosphate

• The triose phosphate is used to regenerate RuBP

• This cycle is called the Calvin cycle

BIBLIOGRAPHY

• http://science.hq.nasa.gov/kids/imagers/ems/roygbiv_waves.gif

• http://www.agri.huji.ac.il/~zacha/images/chloroplast.jpg

• http://www.microscopy.fsu.edu/cells/chloroplasts/images/chloroplastsfigure1.jpg