The details behind anabolic cellular energetics Photosynthesis The details behind anabolic cellular energetics

Photosynthesis—chloroplasts Chloroplast structure Function allowed Large membrane surface area of the thylakoids Greater absorption of light Small space (lumen) within the thylakoids Faster accumulation of protons Stroma region similar to the cytosol of the cell Area for the enzymes necessary for the Calvin cycle to work Double membrane on the outside Isolates the working parts and enzymes from the cytosol All photosynthetic processes take place within the chloroplast (unlike respiration & mitochondria) Membrane-bound organelle with evidence of endosymbiosis own membrane, own DNA, large size Found mostly in leaves, but can be found in other plant organs

Photosynthesis—light dependent Excited electron acceptor e- Electron carrier (PQ) cytochrome complex (electron carrier) Energy of electrons Electron carrier H+ Photosystem II Photosystem I

Photosynthesis—light dependent cytochrome complex (electron carrier) Photosystem II Excited electron acceptor e- Electron carrier (PQ) H+ Electron carrier Energy of electrons Photosystem I

Photosynthesis—light dependent Excited electron acceptor e- Ferredoxin (electron carrier) NADP Reductase Energy of electrons NADP+ + H+ NADPH Photosystem I

Photosynthesis—light dependent Final electron acceptor is NADPH

Photosynthesis—light dependent Electrons replaced via photolysis of water Only known system in nature where oxygen is oxidized As energy level of electrons falls, H+ pumped into thylakoid space, creates gradient Chemiosmosis results in H+ coming through ATP synthase, generating ATP in stroma Photophosphorylation The energy that is used to add a phosphate to ADP to create ATP comes from the sun

Photosynthesis—light dependent Respiration chemiosmosis Photosynthesis chemiosmosis ETC chain embedded in the membrane of the cristae ETC embedded in the membranes of the thylakoids Energy released when e- are exchanged from one carrier to another Same! Released energy used to pump H+ ions into the intermembrane space Released energy used to actively pump H+ ions into the thylakoid space H+ ions come from the matrix H+ ions come from the stroma H+ ions diffuse back into the matrix through ATP synthase H+ ions diffuse back into the stroma through ATP synthase ATP synthase catalyses the oxidative phosphorylation of ADP to form ATP

Photosynthesis—light independent NADPH and the ATP generated in the light dependent reactions needed to drive this process CO2 fixed (integrated into a non-gaseous molecule) into glucose Occurs in the stroma

Photosynthesis— light independent GP - Glycerate 3-Phosphate TP – triose phosphate (Glyceraldehyde 3-phosphate) A total of 12 ATP and 12 NADPH molecules needed for ONE glucose molecule TP, first molecule made in glycolysis (these are reverse rxns) RUBSICO—a lot of it b/c not very efficient & it’s a part of a VERY important process— carbon fixation RUBISCO

Photosynthesis—rates Three main factors you need to know that affect photosynthetic rates: Light intensity CO2 concentration Temperature Be able to explain the different aspect of each graph in terms of why it looks the way it does Also be able to draw the graphs on your own

Photosynthesis—rates Distance from light source and power can affect the light intensity

Photosynthesis—rates Optimum temperature As temperature increases, enzyme rates increase until the point of denaturation

Photosynthesis—rates CO2 saturation for most plants 50 350 500 1000 2000 carbon dioxide/ppm in atmosphere Only so much RuBP to react with (and other limitations)

Photosynthesis—cyclic vs non-cyclic photophosphorylation

Photosynthesis—cyclic vs non-cyclic photophosphorylation OFF TO THE CALVIN CYCLE e– e– NON-cyclic photophosphorylation Where do the replacement electrons come from? Photolysis of H2O There is a cyclic photophosphorylation too ATP produced, NO NADPH sent to Calvin cycle H+ H2O e— ½ O2 H+ e—

Photosynthesis—cyclic vs non-cyclic photophosphorylation

Photosynthesis—cyclic vs non-cyclic photophosphorylation e_ gets recycled: continually providing energy to establish H+ gradient Occurs when light is not a limiting factor + NADPH levels are high in the chloroplasts Extra ATPs produced head to Calvin cycle allowing it to occur more rapidly