Chapter 8--Photosynthesis 8-1 Energy and Life A. Autotrophs and Heterotrophs 1. Autotrophs (auto-self, trophe-food) a. Plants/algae use sunlight energy to produce food 2. Heterotroph (hetero-other) a. Obtains energy from consumed food B. Chemical energy and ATP 1. Adenosine triphosphate (ATP) a. Principal chemical compound to store and release energy b. basic energy for all cells

c. ATP composition -adenine (nitrogen compound) -ribose (5-carbon sugar) -3 (tri) phosphate groups *groups give the ability to store/release energy -ATP=a fully charged battery 2. Storing energy a. ADP (adenosine diphosphate) -2 phosphate groups -gains/stores energy by adding a phosphate group to make ATP -ADP+PATP -ADP=a half charged battery

b. Adenosine monophosphate -1 phosphate group -gains/stores energy by adding 1 phosphate to make ADP -AMP+PADP -very low charged battery 3. Releasing energy a. To release energy, bonds between phosphates are broken ATP-PADP ADP-PAMP b. ATP powers -active transport -protein synthesis -muscle contractions c. ATP is for quick energy only, does not store for long periods

8-2 Photosynthesis : An Overview A. Investigating Photosynthesis 1. Van Helmont’s experiment (1643) a. Found mass of soil, the planter, and seedling watered the plant for 5 years after 5 years the tree had gained 75 kg with the soil mass unchanged Conclusion: mass gained came from the water b. Experiment accounts for “hydrate” (water) part of carbohydrate of photosynthesis c. Van Helmont did not realize that CO2 contributed to tree growth

2. Priestley’s Experiment (1771) a. Lighted candle was covered w/jar and immediately went out Conclusion: “Something” in air kept the candle burning b. Candle and live plant spring (mint) was covered for several days Candle was quickly re-lighted, covered, and burned for a longer period of time c. Conclusion of exp.: Plant sprig gave off substance the candle needed to burn (O2) 3. Ingenhousz (1779) a. By re-doing Priestley’s exp. he showed the experiment worked better in light b. Conclusion: Light is necessary to produce O2

B. Photosynthesis Equation 4. Scientists discovered that plants transform CO2 and H2O into carbohydrates when in light and gives off O2 B. Photosynthesis Equation 1. 6CO2 + 6H2O (in light)  C6H12O6 + 6O2 2. carbon dioxide + water in light yields glucose and oxygen 3. Sunlight energy is used to convert carbon dioxide and water into sugars and oxygen

a. Different wavelength give colors C. Light and Pigments 1. Visible spectrum—light wavelengths a. Different wavelength give colors b. Wavelengths combined give “white” light 2. Pigments a. Gathers sunlight energy b. Principal pigment is chlorophyll -2 types of chlorophyll *chlorophyll a—absorbs light in blue- violet/red region of visible spectrum *chlorophyll b—absorbs light in blue/red region c. Chlorophyll does not absorb light well in green region of spectrum -green light is reflected—plants appear green -red/orange light is also reflected (carotene-carrots, red—tomatoes)

8-3 Reactions of Photosynthesis A. Inside a Chloroplast a. Handout B. Electron Carriers 1. Sunlight excites chlorophyll electrons to gain energy a. Chlorophyll electrons require special carriers b. NADP+ -carrier molecule -gains 2 electrons and a hydrogen ion (H+) and converts NADP+  NADPH -NADPH traps and holds sunlight energy (electrons) in chemical form -NADPH carries energy to other cell areas to be used in photosynthesis

C. Light-Dependent Reaction 1. handout D. Light-Independent Reaction (Calvin Cycle/Dark) 1. handout E. Factors Affecting Photosynthesis 1. Lack of water can slow/stop photosynthesis a. Dry condition plants have a waxy coating to reduce water loss 2. Temperature Range of OoC--35oC allows enzymes to work best a. Temp. above/below damage enzymes slowing down photosynthesis 3. Light intensity affects photosynthesis rate a. Increasing light intensity increases photosynthesis b. After a certain level of light intensity plant reaches its maximum rate of photosynthesis c. Light varies from plant type to plant type