Photosynthesis

Last Topic= How do we burn glucose to make energy This Topic=How do organisms make glucose

Photosynthesis = Capture Sunlight energy and convert it into the chemical energy stored in glucose + 6H2O 12

What do we mean by “sunlight energy?”

Sunlight Light=radiation Radiation travels in waves Frequency=number of waves in a defined time

Wavelengths Visible Light Spectrum

Photons Although a wave, light travels in energy bundles called PHOTONS

What part of a plant absorbs these photons?

Photosynthetic Pigments Chlorophyll a Absorbs red and blue, Reflects green Chlorophyll b Carotenes Reflects Orange Xanthophylls Reflects Yellow

Chlorophyll Structure More Similar or Different?

Purpose of Accessory Pigments Ex. Carotenes and Xanthophylls Capture additional wavelengths of light and pass energy onto the chlorophylls

Who has which pigments? Plants, green algae, euglenoids: Chlorophyll a and b and carotenoids Brown algae, diatoms, dinoflagellates: Chlorophyll a and c and carotenoids Red Algae: Chlorophyll a, carotenoids and phycobilins

Brown Algae Red Algae Tide Green Algae

Absorption Spectrum

In the absence of sunlight which color of light bulb is best to grow plants?

Best: Red and Blue (Absorbed) Worst: Green (Reflected)

Chloroplast Anatomy Grana= Stacks of sacs filled with Chlorophyll = Each sac is called a thylakoid = Reactions occur along the membranes of the thylakoids Stroma=Gel-like material around grana

Reactions of Photosynthesis Light-Dependent Reactions Held in Grana Need Sunlight or Red or Blue light Light-independent reactions (a.k.a.Carbon Fixation Reactions or Calvin Cycle) Held in Stroma Can occur day or night

Light-Dependent Reactions

Light-Dependent Reactions

Light-Depdendent Reactions Photosystem II molecules of chlorophyll absorb light and get excited. H2O is split (Photolysis) Electrons passed to thylakoid cytochromes in membrane for electron transport/chemiosmosis Free H+s created O2 waste created

Light Reactions 3. ATP created along ETC chain 4. Electrons from Photosystem II passed to Photosystem I chlorophyll 5. Photosystem I gets excited with absorption of light and electrons passed to 2nd ETC 6. Last receiver of electrons is NADP+ (with Hs of photolysis you get NADPH)

Light Reactions

Light-Independent Reactions (In Stroma) 3 Cycles goes 6 times around to make 1 glucose

Overall Photosynthesis

Factors affecting photosynthesis Light intensity Temp Water minerals

C4 and CAM Plants C4 CAM Corn, Sugarcane, Tropical Grasses On hot days they close their stomata to conserve water Altered photosynthesis procedure CAM Cacti Close stomata during day