So…how do we get the energy we need to survive? Unit 4 Cell Energetics! So…how do we get the energy we need to survive?

Part 4: Photosynthesis overview, chloroplast structure & pigments Unit 4 Cell Energetics! Part 4: Photosynthesis overview, chloroplast structure & pigments

Where does energy originally come from?? Make sure to state energy comes from the sun (except in deep sea conditions where chemicals power life from sulfur vents…cool!)

Photosynthesis is the process by which certain organisms use light energy to make sugar and oxygen gas from carbon dioxide and water What does it need? (Input) What does it make? (Output) Light energy PHOTOSYNTHESIS 6 CO2 + H2O Carbon dioxide Water C6H12O6 O2 Glucose Oxygen gas

PS vs CR Photosynthesis Cellular Respiration Inputs: Outputs: Make a table!! Photosynthesis Plants & some bacteria Inputs: Light energy H2O CO2 Outputs: O2 C6H12O6 Cellular Respiration Plants & animals Inputs: C6H12O6 O2 Outputs: CO2 H2O ATP

Chloroplast structure Be able to ID the following: Inner membrane* Outer membrane* Granum Thylakoid Stroma *supports the endosymbiotic theory

Endosymbiotic Theory? A larger cell (pre-eukaryote) engulfed a smaller prokaryote  the smaller one provided energy  instead of “eating” the small bacteria they became bffs Evidence that supports this: Chloroplasts & mitochondria have their OWN DNA!!!  Chloroplasts & mitochondria have ribosomes & cytoplasm! Chloroplasts & mitochondria have two layers of membrane!

Leaf Anatomy Mesophyll  chloroplast-rich cells found under the epidermis Stomata  openings under the leaf that allow gas to pass in & out

Chloroplasts… Found in mesophyll 1 mesophyll cell may have 30 chloroplasts! (remember the pond scum?)

Photosynthesis Overview Light reactions (LDR) Depend on light Occur in Thylakoid Membrane Light Independent reactions (LIR) Does NOT need light Occurs in the Stroma

Electromagnetic spectrum

Photosynthesis background Pigments this is what absorbs the light energy from the sun it excites electrons making it unstable Photosystems (PS 1 & PS 2) Made of pigments & proteins

Pigments Chlorophyll Chlorophyll a  main pigment  blue-green Chlorophyll b  accessory pigment  yellow-green Other accessory pigments  absorb different wavelengths of light Carotenoids  yellow-orange Xanthophyll yellow Rhodophyll  red Fucoxanthin  brown Why are plants green? Why are plants changing color?

Unit 4 Cell Energetics! Part 5 LDR, ETC & Gradients

Photosynthesis Overview Light reactions (LDR) light energy  chemical energy (ATP and NADPH) and produce O2

LDR Inputs? Outputs? Location?

Light Dependent Reaction (LDR)/Photophosphorylation

Photosystems Consist of There are 2 Pigments (chlorophyll b, carotenoids & xanthophyll) Proteins! There are 2 Photosystem 1 The last photosystem in the Light Dependent Reaction (LDR) Photosystem 2 The FIRST photosystem in the LDR Photosystem 2 comes first, but has the #2 after it because we discovered it second…

Photosystems Process: Photon (light energy) absorbed by pigments  excites e- in pigment e- jump to higher levels  eventually reaches the reaction center (chlorophyll a)  transfers energy to the reaction center  passed back down through an ETC in LDR

Summarize the flow of energy: Electron Carriers Act like a car to transport electrons NADP+ is an “empty” car NADPH is a “full” car Summarize the flow of energy: Light energy to photosystem 2  electrons excited  electron passed to ETC  electrons hit photosystem 1  electrons then go to ANOTHER ETC  electrons end up in the electron carrier (NADPH)

But WHY??????

Cytochrome complex synthase reductase LIGHT REACTOR NADP+ ADP ATP NADPH CALVIN CYCLE [CH2O] (sugar) STROMA (Low H+ concentration) Photosystem II H2O CO2 Cytochrome complex O2 1 1⁄2 2 Photosystem I Light THYLAKOID SPACE (High H+ concentration) Thylakoid membrane synthase Pq Pc Fd reductase + H+ NADP+ + 2H+ To Calvin cycle P 3 H+ 2 H+ +2 H+

ETC, Chemiosmosis & ATP Synthase ATP synthesis in light reactions electrons (e-) are passed along a chain of proteins (called the ETC) in the membrane  H+ pumped into Thylakoid space (chemiosmosis)  this is active transport! H+ diffuse back across the membrane through ATP synthase  powers the phosphorylation of ADP to produce ATP (photophosphorylation)

Photophosphorylation http://vcell. ndsu. nodak

Light Dependent RXN animation http://www.science.smith.edu/departments/Biology/Bio231/ltrxn.html http://vcell.ndsu.nodak.edu/animations/photosynthesis/movie-flash.htm

Part 4 Light Independent Reaction Cell energetics Part 4 Light Independent Reaction

Photosynthesis Overview Light Independent Reactions (LIR…aka: Dark reactions and Calvin Cycle) Using ATP and NADPH from the light reactions form sugar from CO2

Calvin Cycle/Light Independent Reactions Occur in the dark or the light Occurs in the stroma 3 steps Carbon fixation Reduction Regeneration of RuBP

Step 1: Carbon Fixation RuBP 5 C sugar w/2 Phosphates Rubisco (nickname for an enzyme) adds CO2 Creates an unstable 6 C molecule that splits Creates 2 3-C molecule

Step 2: Reduction 3-C molecule gets phosphorylated by ATP (gets it’s energy) Electron carrier adds an electron (MORE energy!) Produces G3P (PGAL) some G3P  glucose most G3P  regenerate RuBP Adds a phosphate & energy, then electron carrier adds MORE energy new name PGAL or G3P (some of which makes glucose…but most goes to regenerate RuBP

Step 3: Regeneration of RuBP 1 G3P moves out to eventually become glucose G3P  rearranged into RuBP Requires input of 3 ATP Takes 6 turns of cycle  1 glucose