Chapter 6 Photosynthesis

Chapter 6 Photosynthesis I. Definition: process where autotrophs (plants) make their own food using sunlight. II.Capturing light energy A. Chloroplasts – organelles in plants where photosynthesis takes place. 1. System of membranes inside cell thykaloids arranged in flattened sacs and contain pigments a. Stacks called grana b. Solution around grana is called stroma. 2. Green pigment is called chlorophyll. 3. Other pigments carotenoids – yellow, orange, and brown. B. Light from the sun appears white but is made of a variety of colors: visible light spectrum. C. The shorter the wavelength, the more energy. 1. Blue is the shortest – absorbs the most. 2. Then violet and red. 3. Chlorophyll reflects green – does not absorb it. D. ATP: adenosine triphosphate 1. Main source of energy for all living things. III.Overall reaction of photosynthesis A. 6CO2 + 6H2O →light energy→ C6H12O6 + 6O2 IV.Stages of Photosynthesis A. Light reactions – light dependant, occur in grana 1. Chlorophyll absorbs light

2. Electrons absorb light energy and electrons become excited. 3. Water H2O is split and O2 gives off. B. Dark reactions (Calvin Cycle) – light independent 1.

CO2

is used and glucose C6H12O6 is formed.

2. Can take place in the light or dark – light is NOT needed. 3. O2 is given off. C. Factors affecting Photosynthesis 1. More light, more photosynthesis *up to a point*.