Chapter 9 Energy in the Cell

ATP Adenosine triphosphate Quick source of energy Does not last long The energy is stored in the bonds between the phosphates

Structure of the Chloroplast

Chloroplast Contains pigments Molecules that absorb light of a specific wavelength Chlorophyll – most common – absorbs most wavelengths EXCEPT green Carotenoid – red, orange, yellow Carotenes Xanthophylls

Photosynthesis Process that captures the sun’s energy and transforms it into simple sugars 6CO2 + 6H2O  C6H12O6 + 6O2 Occurs in the chloroplast Two phases: Light dependent – occurs in the membrane of the thylakoid – makes ATP Light independent – occurs in the stoma of the chloroplast - makes simple sugars

Light Dependent Reactions Requires sunlight E from the light is transferred to e- These excited e- enter the e- transport chain of photosystem II Photosystem – a series of proteins embedded in the membrane of the thylakoid

Photosystem II and I P II – e- is passed down the e- transport chain – makes ATP or pumps H+ into the center of the thylakoid disc at each step P I – re-energized e- is passed down a second e- transport chain @ the end, the e- is transferred to NADP Forms NADPH which is used in the light- independent reactions NADP is a carrier – it just transports the e- (like a taxi)

The e- Taken From the Chlorophyll Must be Replaced! In PII water is split: photolysis Creates oxygen, H+, and e- Oxygen – released H+ - pumped into the thylakoid to create a concentration gradient e- returned to the chlorophyll

What happens to the H+? An enzyme ATP synthetase allows the H to move down the concentration gradient and makes ATP

Light-Independent Reactions Calvin Cycle (C3) Make sugar from CO2 Carbon fixation Occurs in the stroma of the chloroplast

C4 and CAM Used by plants in dry climates. In dry climates, the stomata (pores) in the leaves need to stay closed to prevent water loss. This causes the CO2 levels to drop. If not enough CO2 is available C3 plants will begin grabbing O2 and burning sugars instead of making them (photorespiration) The protein in the light-independent rxn is more efficient at grabbing CO2