PHOTOSYNETHESIS Biology B Rhodes Holt Ch. 9.2

Review of Carbon Cycle PHOTOSYNTHESIS RESPIRATION CO2CO2 Glucose or fuel or organic compound combustion decomposition sunlight Oxygen H2OH2O

9.2 Photosynthesis (pgs. 202 – 207)  Harvesting Light Energy  What is the role of pigments in photosynthesis?  Two Electron Transport Chains  What are the roles of the electron transport chains? (ETC ….. vs etc. which is ‘et cetera’ or “and all” and not ect.)  Producing Sugar  How do plants make sugars and store extra unused energy?  Factors That Affect Photosynthesis  What are three environmental factors that affect photosynthesis?

Harvesting Light Energy  Electromagnetic Radiation  Pigments  Electron Carriers Plants convert sunlight (solar energy) into chemical energy. This chemical energy can be used for biological processes in nearly all living things.

Harvesting Light Energy  Plants, algae and a few prokaryotes capture 1% of light energy that reaches Earth  Light energy converted to chemical bond energy  Process is called PHOTOSYNTHESIS  Chloroplast is organelle that provides surface area for photosynthesis  CHLOROPLAST double membrane inner membrane more selective space inside called stroma additional membranes called thylakoid membranes ( sacs) that are embedded with chlorophyll molecules

Review of Chemical Energy  Organisms use and store energy in chemical bonds  Specifically in the C-C, C-H bonds of organic compounds  All of this energy originally comes from the sun  Photosynthesis is the process used by living organisms to use solar energy to create C-C bonds in organic compounds  Autotrophs (like plants) are able to make their own organic compounds (like carbs/’sugar’ and amino acids for proteins and fatty acids for lipids, etc.)  Heterotrophs (everything else) must get their energy and their supplies in a pre-made form. (sugar, protein, fat and even DNA)

Light Energy  Light is electromagnetic radiation  Light has dual nature: waves and particles (photons)  Solar energy is both light energy & heat energy  Different wave lengths ( l ) or colors have different amounts of energy

The Splitting of Water  Light energy lands on, and is collected by pigments in the photosystems, where they “excite electrons”  The energy splits water molecules into H 2 and O 2. The O 2 is released by the plant  The H 2 is further split into H+ and electrons (e-)  Electrons are recycled to photosystems  H+ is added to NADPH – the first energy storing compound

Pigments  Pigments are chemical compounds that absorb specific wavelengths of light. Other colors of light are reflected.  Chlorophyll absorbs RED and BLUE and reflects green – so the leaves look green.  Chlorophyll (chemical) in embedded in the inner portions of the chloroplasts membranes (called thylakoid membranes)  Many other accessory pigments in most plants, in addition to chlorophyll a and chlorophyll b, like xanthophyll and carotene

Equation for Photosynthesis  “using light to make or synthesize something”  6CO 2 + 6H 2 O C 6 H 12 O 6 + 6O 2  You should know this equation for all future quizzes, tests and the final exam sunlight chlorophyll

Chloroplast details; you drew these pictures

Electron Transport Chains  Producing ATP  1. split water  2. hydrogen ion pumps (thylakoid membrane)  3. ATP synthase – move H back in other direction  Producing NADPH  Electrons are replaced  H+ added to NADP+ making NADPH  Producing Sugar  Carbons are glued together (C-C) this takes energy which comes from ATP and NADPH and requires CO2

Factors Affecting Photosynthesis 1. Light intensity (longer days, brighter sunlight, closer to equator = more photo.) 2. Carbon dioxide (CO 2 ) concentration (lots of available CO 2 diffuses into stomata and spongy mesophyll of leaves 3. Temperature (lots of enzymes directing these reactions, all enzymes are proteins that function best in specific temperature ranges) Think about bags with grass seed….. Did you alter the amount of light, did you alter the amount of CO2, did you alter the temperature? Independent Variables – Dependent Variables - Controls

KEY WORDS  Pigment  chlorophyll  Chloroplast  Thylakoid  Calvin cycle  “embedded”  Wave length  Light capturing reactions  Carbon fixing reactions  Photosynthesis  plants  Surface area  Light  Electron carrier  ATP  ATP synthase  - ase  - ose  Energy storing compound  NADPH  CO 2  H 2 O  O2  Concentration