4.7 Photosynthesis Overview Unit 4: Cell Energy 4.7 Photosynthesis Overview

Photosynthesis Uses energy from sunlight to convert water and carbon dioxide (reactants) into high energy sugars and oxygen (products)

Photosynthesis Sunlight is the ultimate energy for all life on Earth Plants then use sugars to produce complex carbohydrates and provide energy Plants store energy from the sun in the chemical bonds of sugars Chemical energy is released as ATP during cellular respiration BOTH IN PLANT AND ANIMAL CELLS

Overall Equation

Sunlight Sunlight is a mixture of different wavelengths our eyes perceive as white Colors include red, orange, yellow, green, blue, indigo, and violet The sun’s energy travels to Earth as light

Chloroplast Organelle where photosynthesis occurs

Structure Contain an inner and outer membrane Thylakoid: saclike photosynthetic membranes Grana: Interconnected stacks of thylakoid Stroma: Fluid outside the thylakoid

Thylakoid Membrane Thylakoid Space Granum Stroma Outer Membrane Inner Membrane

Pigments Pigments are light-absorbing molecules that gather the sun’s energy Pigments are located in the thylakoid membranes

Chlorophyll A plant’s principle pigment Chlorophyll absorbs visible light especially well Chlorophyll absorbs blue-violet and red wavelengths of light best Chlorophyll reflects green wavelengths, causing them to appear green

Fall Colors Plants also contain red and orange pigments, such as carotene, that absorb light in other regions of the spectrum. As temperatures drop later in the year, chlorophyll pigments break sown first, leaving red and orange pigments to be seen

Reactions in Photosynthesis Light Dependent Reactions Light Independent Reactions Require direct involvement of light Use sun’s energy to produce ATP Takes place in the thylakoids Water is required as a sources of electrons and hydrogen ions Oxygen is released No Light is required ATP and NADPH are used to make sugars Takes place in the stroma Carbon dioxide is required

Questions In which organisms does photosynthesis occur? In which organisms does cellular respiration occur? Why do leaves change colors in the fall? What does photosynthesis produce?