The process of making food Photosynthesis The process of making food

Overview: The Process That Feeds the Biosphere Photosynthesis Is the process that converts solar energy into chemical energy

Plants are photoautotrophs They use the energy of sunlight to make organic molecules from water and carbon dioxide

(b) Multicellular algae (c) Unicellular protist Photosynthesis Occurs in plants, algae, certain other protists, and some prokaryotes These organisms use light energy to drive the synthesis of organic molecules from carbon dioxide and (in most cases) water. They feed not only themselves, but the entire living world. (a) On land, plants are the predominant producers of food. In aquatic environments, photosynthetic organisms include (b) multicellular algae, such as this kelp; (c) some unicellular protists, such as Euglena; (d) the prokaryotes called cyanobacteria; and (e) other photosynthetic prokaryotes, such as these purple sulfur bacteria, which produce sulfur (spherical globules) (c, d, e: LMs). (a) Plants (b) Multicellular algae (c) Unicellular protist 10 μm 40 μm (d) Cyanobacteria 1.5 μm (e) Pruple sulfur bacteria Figure 10.2

Heterotrophs Obtain their organic material from other organisms Are the consumers of the biosphere

Chloroplasts: The Sites of Photosynthesis in Plants The leaves of plants Are the major sites of photosynthesis Vein Leaf cross section Figure 10.3 Mesophyll CO2 O2 Stomata

Chloroplasts Are the organelles in which photosynthesis occurs Contain thylakoids and grana Chloroplast Mesophyll 5 µm Outer membrane Intermembrane space Inner Thylakoid Granum Stroma 1 µm

Tracking Atoms Through Photosynthesis: Scientific Inquiry Photosynthesis is summarized as

The Two Stages of Photosynthesis: A Preview Photosynthesis consists of two processes The light reactions (light-dependent) -Needs Light! The Calvin cycle (light-independent) -Does NOT need light!

Light-Dependent Reaction The light reactions Occur in the grana Split water, release oxygen, produce ATP

The Calvin Cycle (Light-Independent Reaction) Occurs in the stroma Forms sugar from carbon dioxide, using ATP for energy The Calvin Cycle (Light-Independent Reaction)

Overview of Photosynthesis CO2 Light LIGHT REACTIONS CALVIN CYCLE Chloroplast [CH2O] (sugar) NADPH NADP + ADP + P O2 Figure 10.5 ATP

3 Factors that Affect Photosynthesis Carbon Dioxide (CO2) Without CO2, the plant would not have one of the raw materials needed in the photosynthesis equation CO2 is used in the first step of the Calvin Cycle Temperature The temperature must be in the appropriate range for the plant in order for photosynthesis to properly occur

3 Factors that Affect Photosynthesis Intensity of Light If the intensity of light is lower, the available energy for photosynthesis is lower. If light is not available at all, the light-dependent reactions cannot occur (nor can they provide the materials used in the light-independent reactions)

Exit Slip What are the reactants for photosynthesis and the products?