Photosynthesis The Flow of Energy

ATP adenosine triphosphate chemical compound used by living things to store energy When the bond between two phosphate groups is broken – energy is released ATP  ADP + Pi

Photosynthesis Jan van Helmont – plants gain their mass from water Joseph Priestly – plants release oxygen Jan Ingenhousz – light is necessary for plants to produce oxygen 6CO2 + 6H2O  C6H12O6 + 6O2

Light Visible spectrum – ROYGBIV Red = longest wavelength Violet = shortest wavelength Color of an object is determined by the color the object reflects Plants gather light using pigments

Chloroplasts and Pigments chloroplast – organelle where photosynthesis occurs chlorophyll – a green pigment, most important in photosynthesis carotenoids – yellow, orange and red pigments absorbed light is transformed from light energy to chemical energy

Inside a Chloroplast thylakoids – saclike photosynthetic membranes grana – stacks of thylakoids stroma – space outside the thylakoids

Overview of Photosynthesis photosynthesis occurs only in producers endergonic reaction – a chemical reaction that uses or stores energy Two steps of photosynthesis Light Reactions Calvin Cycle

Light Reactions require light use energy from light to produce ATP and NADPH occurs in the grana energy from “excited electrons” is used to bond ADP and Pi to form ATP

Light Reactions 3 main events Light energy is absorbed by the chlorophyll and ATP is made Water is split into hydrogen ions, oxygen and electrons The hydrogen ions are used to make NADPH

Light Reactions Inputs: Light Water Outputs: ATP NADPH Oxygen (O2)

Calvin Cycle Also called the dark reactions or light-independent reactions process of synthesizing sugars occurs in the stroma does not require light converts CO2 to sugar

Calvin Cycle 3-carbon sugars are produced Some used as energy sources Some converted to lipids, amino acids, parts of nucleic acids Two can combine to form 6-carbon sugars

Calvin Cycle Inputs: ATP NADPH CO2 Outputs: Sugars

In the end… a single 6-carbon sugar is formed from 6 molecules of carbon dioxide plants use the sugar for energy and to build more complex carbohydrates such as starches and cellulose other organisms eat the plants and use the energy stored in carbohydrates

Factors Affecting Photosynthesis Shortage of water Can slow or stop photosynthesis Temperature Photosynthesis requires enzymes that function best between 0°C and 35°C Intensity of light Increasing light intensity increases the rate of photosynthesis