Chapter 8: Energy and Photosynthesis

Energy and Photosynthesis Energy is necessary for all life Plants and green organisms: Trap light energy in the form of sunlight and store it for later use All other organisms: Eat green plants to obtain energy

Adenosine Triphosphate (ATP) Energy molecule Composed of: Adenosine molecule Ribose sugar 3 phosphate groups

ATP becomes available for a cell to use when the bonds between the phosphate groups are broken Releases energy when a phosphate group is removed Bond breaks between the 2nd and 3rd phosphate groups Results in adenosine diphosphate (ADP) ATP is a small molecule Stored energy (ex: a battery) Cells use energy to maintain homeostasis

Where can I get some atp?!!!

Photosynthesis Photo-: means light Synthesis: to put together Process that uses the sun’s energy to make simple sugars 2 phases Light-dependent reactions Light-independent reactions

History Van Helmont (1600’s) Priestley (1700’s) Ingenhouz Planted seedling in pot of soil, watering it regularly Concluded plant mass comes from the water Priestley (1700’s) Candle with glass jar cover  flame died Mint sprig and candle with glass jar cover  flame burned Conclusion: plants release oxygen Ingenhouz Supported Priestley  will occur only when mint plant is exposed to light

Photosynthesis Requirements (raw materials) Light (sun) Carbon Dioxide (from the air) Taken in to plants through little openings in the leaves called stomata Water (from the ground) Taken in through the roots of plants Chlorophyll and enzymes in the plant Rate of photosynthesis depends on: The availability of sunlight, CO2, and H2O The intensity (brightness) of light Temperature (20-35º C is optimal)

White light  mixture of different wavelengths of light Visible spectrum  ROYGBIV Pigments: molecules that absorb specific wavelengths of sunlight Ex: Chlorophyll (in chloroplasts): a and b Absorbs well in blue and red light Absorbs most wavelengths except green (reflects green light) Makes plants appear green Other plant pigments: Xanthophyll: yellow pigment Carotene: orange pigment

Equation: 6CO2 + 6H2O + light  C6H12O6 + 6O2 Carbon Dioxide + Water  Sugar + Oxygen gas Chloroplast: cell organelle where photosynthesis occurs Light-dependent reactions take place in the thylakoid membrane (contains pigments) Photosynthesis Song

Picture of a chloroplast: Grana: stack of thylakoids Stroma: outside of the thylakoids Photosystem: clusters of pigment and protein that absorb light energy (found in thylakoids)

Light-Dependent Reactions 1st phase Requires light, NADP Converts light energy into chemical energy ATP produced fuels light-independent reactions NADP: electron carrier Holds 2 high-energy electrons and H+ Converts NADP+ to NADPH

Occurs in the grana of chloroplasts Splits water (photolysis) Light reactions use trapped light energy to convert ADP to ATP and NADPH Occurs in the grana of chloroplasts Splits water (photolysis) H: needed to make glucose O: released as a waste product into the atmosphere

Light- dependent reactions H2O CO2 Light NADP+ ADP + P Light- dependent reactions Calvin cycle Chloroplast O2 Sugars

Light ATP H+ (in grana) (in stroma) H2O in CO2 in C6H12O6 (glucose) Light reactions C6H12O6 (glucose) Dark reactions H+ (in grana) (in stroma) H2O as waste O2 as waste

Chapter 8 Walkaround: The light-dependent reactions take place within the __________ membranes. In the light-dependent reactions, the gas ____ is produced. High-energy sugars are produced during the _______ reactions.

Light-Independent Reactions Does not require light Called dark reactions or the Calvin cycle Process of actually making glucose (uses CO2 to make simple sugars/starches) Uses energy from ATP and NADPH Can occur in the light or the dark Requires enzymes (ATP synthase) Occurs in the stroma of chloroplasts

Summary of Photosynthesis Any glucose not used immediately can be stored as starch or sugars Chemosynthesis Process of making food from inorganic compounds Does not use sunlight Uses Sulfur in deep sea vents Summary of Photosynthesis

Autotrophs Use photosynthesis or chemosynthesis Make their own food

Autotrophs Plants, Cyanobacteria, Algae - contain chlorophyll and carry out photosynthesis Bacteria deep in the ocean – (no light available) carry out chemosynthesis using hydrogen sulfide coming from hydrothermal vents in the ocean floor

Importance of plants Plants - NatGeo