Lesson Overview Lesson Overview Photosynthesis: An Overview THINK ABOUT IT How would you design a system to capture the energy of sunlight and convert it into a useful form? This issue has been solved through the natural design of plants – maybe we can learn a trick or two from them.

Lesson Overview Lesson Overview Photosynthesis: An Overview Important Root Words Root Word Meaning Photo Chloro -phyll Stome Xantho Light Green Leaf Mouth Yellow

Lesson Overview Lesson Overview Photosynthesis: An Overview All Organisms Need Energy All organisms require energy to live. There are two main ways to obtain this necessary energy: Cells use energy trapped in chemical bonds. When these bonds are broken, energy is released for cellular activities. When cells use several linked chemical pathways to create the energy needed, this is called a biochemical pathway. AUTOTROPHS HETEROTROPHS

Lesson Overview Lesson Overview Photosynthesis: An Overview Light Energy from the sun travels to Earth in the form of light. Sunlight is a mixture of different wavelengths, many of which are visible to our eyes. The wavelengths of the visible spectrum appear to us as “white light.” Our eyes see the individual wavelengths of the visible spectrum as different colors: red, orange, yellow, green, blue, indigo, and violet.

Lesson Overview Lesson Overview Photosynthesis: An Overview Pigments Plants gather the sun’s energy with light- absorbing molecules called pigments. The plants’ principal pigment is chlorophyll. There are two main types of chlorophyll: chlorophyll a chlorophyll b

Lesson Overview Lesson Overview Photosynthesis: An Overview Copyright Pearson Prentice Hall Light and Pigments Chlorophyll absorbs light well in the blue-violet and red regions of the visible spectrum. Wavelength (nm) Estimated Absorption (%) Chlorophyll b Chlorophyll a Wavelength (nm)

Lesson Overview Lesson Overview Photosynthesis: An Overview Copyright Pearson Prentice Hall Light and Pigments Chlorophyll does not absorb much light in the green region of the spectrum. Green light is reflected by leaves, which is why plants look green. Estimated Absorption (%) Chlorophyll b Chlorophyll a Wavelength (nm)

Lesson Overview Lesson Overview Photosynthesis: An Overview Pigments Plants also contain red and orange pigments such as carotene that absorb light in other regions of the spectrum.

Lesson Overview Lesson Overview Photosynthesis: An Overview What’s going on here? Why do leaves turn color in the fall?

Lesson Overview Lesson Overview Photosynthesis: An Overview Pigments Most of the time, the green color of the chlorophyll overwhelms the other pigments, but as temperatures drop and chlorophyll molecules break down, the red and orange pigments may be seen.

Lesson Overview Lesson Overview Photosynthesis: An Overview Copyright Pearson Prentice Hall Inside a Chloroplast In plants, photosynthesis takes place inside chloroplasts. Plant Plant cells Chloroplast

Lesson Overview Lesson Overview Photosynthesis: An Overview Copyright Pearson Prentice Hall Inside a Chloroplast Chloroplasts contain thylakoids—saclike photosynthetic membranes. Chloroplast Single thylakoid

Lesson Overview Lesson Overview Photosynthesis: An Overview Copyright Pearson Prentice Hall Inside a Chloroplast Thylakoids are interconnected and arranged in stacks known as grana. A single stack is called a granum. Pigments are located in the thylakoid membranes. The stroma is the fluid region outside the thylakoid membranes. Granum Chloroplast Stroma