Chapter 8: Photosynthesis Section 2: Overview of Photosynthesis

A. Site of Photosynthesis  Photosynthesis takes place in the leaves

 Cross Section of a Leaf:

 Cuticle- Waxy, Non-living layer Prevents the evaporation of water! Prevents the evaporation of water!  Upper Epidermis- One cell layer thick Protection! Protection!  Palisade Mesophyll- Primary location of Photosynthesis for three reasons  Size of Cells- Larger cells contain more Chloroplasts  Location in the Leaf- Closer to the epidermis on top of leaf Receive more sunlight  Perpendicular to Rays of Sun- Allows these cells to receive greater solar radiation!  Spongy Mesophyll- secondary site of photosynthesis- contains AIR SPACES so CO2 can be absorbed and O2 excreted!

Vascular Bundle: “Veins” Carries Water and Dissolved Minerals to leaf from the roots  Vascular Bundle: “Veins” Carries Water and Dissolved Minerals to leaf from the roots Two types of tissue: a. XYLEM- transportts mainly water b. PHLOEM- transports nutrients and organic materials

 Stomata: Opening in the lower Epidermis that allows air to enter and exit the leaf  Guard Cells: Responsible for Opening and Closing Stomata Have Chloroplast- Need Energy

B. The Chloroplast  Site of Photosynthesis in the Leaf Chloroplast Structure A.Thylakoid- Collection of chlorophyll molecules where photosynthesis takes place B.Granum- Stack of thylakoids C.Stroma- Fluid filled space between the chloroplasts membrane and the granum

2. Photosynthetic Pigments A. Chlorophylls Chlorophyll absorbs the blues and reds of visible light, but reflects the greens and yellows Remember, an object appears the color it is because it reflects that wavelength of light! Absorption spectrum Shows what light energy is absorbed by the chloroplast

1. Two Types of Chlorophyll a. Chlorophyll A- Blue green photosynthetic pigment b. Chlorophyll B- Yellow Green pigment

2.Carotenoids- main accessory photosynthetic pigment (beta-carotene..good for your eyes) CAROTenoids are orange/red. We see them when the leaves begin to turn color in the fall but they are always there

3. Xanthophylls/Lycopene- Yellows and Reds Accessory pigments

All of these Aid in Photosynthesis: