1. Photosynthesis

2. Leaf Structure Leaves – site of photosynthesis vein: xylem – carries water phloem* – carries food * always larger in diameter because it transports thick substance (sucrose, like syrup) cuticle – waxy coating on leaf to hold in moisture stomata (stomates) – on undersides of leaf for gas exchange (O 2 & CO 2 ); excess water is also released here guard cells – regulate opening/closing of stomata

3. Photosynthesis Main idea – making glucose equation: 6CO 2 + 6H 2 O + light energy C 6 H 12 O 6 + 6O 2 -building of a complex substance from simpler substances by autotrophs (green plants, algae, some bacteria) in the presence of light -occurs in chloroplasts -2 phases

4. Photosynthesis A.Light reactions or Photo phase or Light dependent reactions (in grana) -occurs only in the presence of light -requires chlorophyll -water molecules are split and energy is stored for later use Step 1: Chlorophyll is “energized” by sunlight -kinetic light energy is transformed to potential chemical energy

5. Photosynthesis (chlorophyll is an energy carrier) -chlorophyll is no longer energized but may be illuminated again and trap more energy Step 2: Water molecules are split. -requires much energy (supplied by energized chlorophyll) Step 3: More energy is trapped in ATP. -ADP in chloroplasts, phosphate groups also present, which can be added to ADP to make ATP.

6. Photosynthesis -potential energy (ATP) remains in the molecule as long as the extra phosphate is attached (stored) -chemical removal of extra phosphate releases energy and forms ADP (kinetic energy) -energy is then received and the process is repeated Step 4: Hydrogen is trapped by NADP -H must be trapped immediately after it is split (from water) or it can escape or combine with O to form water

7. Photosynthesis -NADP traps it (H acceptor) and forms NADPH 2 -This is done on a loan-basis; it is soon passed to another compound Step 5: O 2 released to atmosphere when water is split *This whole series of steps takes place in a split second.

8. Photosynthesis B. Dark reactions or Synthesis phase or Light independent reactions (in stroma) -occur in the presence of light or without light (light independent) Step 1: CO 2 from atmosphere combines with a 5-carbon sugar, RDP (Ribulose Diphosphate) to produce a 6-carbon sugar that is unstable

9. Photosynthesis Step 2: This 6-C compound splits quickly into 2 molecules of PGA (Phosphoglyceric Acid), a 3-C compound Step 3: PGA combines with H brought over by NADPH 2 to form PGAL (Phosphoglyceraldehyde) and H 2 O *This requires energy supplied by ATP formed in the light reactions.

10. Photosynthesis PGAL is the principal product of photo- synthesis because: 1) it can be used directly by the cell as a nutrient 2) it can be broken down to RDP to refuel the reaction 3) it can be built up into glucose **6 turns of this cycle produces one glucose (Calvin cycle)