Chapter 8: Chapter 8: PhotosynthesisPhotosynthesisSection 2: Overview of Section 2: Overview of PhotosynthesisPhotosynthesis

A. Site of PhotosynthesisA. Site of Photosynthesis

Photosynthesis takes place in the leavesPhotosynthesis takes place in the leaves

Cross Section of a Leaf:Cross Section of a Leaf:

Cuticle- Waxy, Non-living layerCuticle- Waxy, Non-living layer Prevents the evaporation of Prevents the evaporation of

water!water! Upper Epidermis- One cell layer thickUpper Epidermis- One cell layer thick

Protection!Protection! Palisade Mesophyll- Palisade Mesophyll- Primary location of Photosynthesis Primary location of Photosynthesis

for three reasonsfor three reasons Size of Cells- Larger cells contain more ChloroplastsSize of Cells- Larger cells contain more Chloroplasts Location in the Leaf- Closer to the epidermis on top of leaf Location in the Leaf- Closer to the epidermis on top of leaf

Receive more sunlightReceive more sunlight Perpendicular to Rays of Sun- Allows these cells to receive Perpendicular to Rays of Sun- Allows these cells to receive

greater solar radiation!greater solar radiation!

Spongy Mesophyll-Spongy Mesophyll- secondary site of photosynthesis- secondary site of photosynthesis- contains AIR SPACES so CO2 can be absorbed and contains AIR SPACES so CO2 can be absorbed and

O2 O2 excreted!excreted!

Vascular Bundle:Vascular Bundle: “Veins” Carries Water and “Veins” Carries Water and Dissolved Minerals to leaf from the rootsDissolved Minerals to leaf from the roots

Two types of tissue:Two types of tissue:

a. XYLEM- transportts mainly water a. XYLEM- transportts mainly water

b. PHLOEM- transports nutrients and organic b. PHLOEM- transports nutrients and organic materialsmaterials

Stomata: Stomata: Opening in the lower Epidermis that allows Opening in the lower Epidermis that allows air to enter and exit the leafair to enter and exit the leaf

Guard Cells: Guard Cells: Responsible for Opening and Closing Responsible for Opening and Closing StomataStomata

Have Chloroplast- Need Have Chloroplast- Need EnergyEnergy

B. The ChloroplastB. The Chloroplast Site of Photosynthesis in the LeafSite of Photosynthesis in the Leaf

1.1. 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 Pigments2. Photosynthetic Pigments

A. ChlorophyllsA. 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 Chlorophyll1. Two Types of Chlorophyll

a. Chlorophyll A- Blue green a. Chlorophyll A- Blue green photosynthetic pigmentphotosynthetic pigment

b. Chlorophyll B- Yellow Green b. Chlorophyll B- Yellow Green pigmentpigment

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 RedsAccessory pigments

All of these Aid in Photosynthesis: