The Working Cell: Energy from Sunlight Chapter 8 The Working Cell: Energy from Sunlight

8.1 Photosynthesis uses light chloroplast: organelle where photosynthesis takes place chlorophyll: chemical compound that gives green color Green parts of plants Chloroplasts concentrated in mesophyll cells mesophyll: inner layer of tissue of a leaf stomata: pores found on surface of leaf that allows gas and liquid exchange CO2 enters; O2 exits Veins carry water to leaves

Chloroplast Similar to mitochondria Inner and outer membranes stroma: thick fluid in inner membrane thylakoids: many disk-shaped sacs Each has a membrane surrounding an interior space grana:stacks of thylakoids

2 Stages of Photosynthesis Light Reaction Convert energy in sunlight to chemical energy Calvin Cycle “Light-independent” Makes sugar from CO2

8.2 Light Reactions electromagnetic energy: travels in waves that can be compared to ocean waves onto a beach Sunlight wavelength: distance between 2 adjacent waves Different in each form Longest=radio (weakest) Shortest= gamma rays

Electromagnetic Spectrum electromagnetic spectrum: range of types of EM energy Visible light between 400nm(violet) and 700nm(red) UV has enough energy to damage cells Specifically proteins and nucleic acids

Pigments pigments: a substances color due to chemical compounds Light can be absorbed, transmitted or reflected A chloroplast’s pigments absorb blue-violet and red-orange very well Does not absorb green Reflected or transmitted

Paper Chromatography Used to observe pigments in a green leaf chlorophyll a: absorbs mainly blue-violet and red-orange and reflects mostly green Major role in photosynthesis chlorophyll b: “helper” absorbs mainly blue and orange and reflects yellow-green. carotenoids: “helper”- absorbs mainly blue-green and reflects yellow-orange Ex. carotein

Stages of Photosynthesis

The Light Reactions Convert energy in sunlight to chemical energy 1. Chlorophyll molecules(membrane of thylakoid) capture light energy 2. Captured energy used to remove electrons from water which splits into oxygen and hydrogen 3. Water’s electrons and H+ ions are used to make NADPH 4. Captured energy used to make ATP

Photosystems photosystems: clusters of chlorophyll and other molecules in the thylakoid Each contain a few hundred pigment molecules Acts like a solar panel

The Calvin Cycle “Light- independent reactions” Makes sugar from CO2 and H+ and electrons carried by NADPH Enzymes located in stroma ATP from light reactions provides energy Requires ATP and NADPH