Energy Harvesting and Usage Photosynthesis and Cellular Respiration

What you must know Photosynthesis Respiration Products and reactants for each stage Light Dependent Photosystem II Photosystem I Light Independent (Calvin Cycle) Where each stage occurs CAM versus C4 strategies for plants Chlorophyll a, b, and carotenoids Products, reactants, location, and order of processes Glycolysis Kreb (Citric Acid) Cycle Electron Transport Chain Fermentation Number of ATP produced

Must Knows – cont. Overall Photosynthesis Overall Respiration Rubisco Proteins and Molecules Equations Rubisco RuBP ATP Synthase Co-enzyme A ATP, ADP, AMP NADH FADH2 NADPH Overall Photosynthesis Overall Respiration

A typical mesophyll cell has 30–40 chloroplasts Chloroplasts are found mainly in cells of the mesophyll, the interior tissue of the leaf A typical mesophyll cell has 30–40 chloroplasts The chlorophyll is in the membranes of thylakoids (connected sacs in the chloroplast); thylakoids may be stacked in columns called grana Chloroplasts also contain stroma, a dense fluid Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Chloroplast Outer membrane Thylakoid Intermembrane space Stroma Granum Fig. 10-3b Chloroplast Outer membrane Thylakoid Intermembrane space Stroma Granum Thylakoid space Inner membrane Figure 10.3 Zooming in on the location of photosynthesis in a plant 1 µm

Tracking Atoms Through Photosynthesis: Scientific Inquiry Photosynthesis can be summarized as the following equation: 6 CO2 + 12 H2O + Light energy  C6H12O6 + 6 O2 + 6 H2O Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

The Two Stages of Photosynthesis: A Preview Photosynthesis consists of the light reactions (the photo part) and Calvin cycle (the synthesis part) The light reactions (in the thylakoids): Split H2O Release O2 Reduce NADP+ to NADPH Generate ATP from ADP by photophosphorylation Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

The Calvin cycle (in the stroma) forms sugar from CO2, using ATP and NADPH The Calvin cycle begins with carbon fixation, incorporating CO2 into organic molecules Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

i Light NADP+ ADP Light Reactions Chloroplast H2O + P Fig. 10-5-1 Figure 10.5 An overview of photosynthesis: cooperation of the light reactions and the Calvin cycle Chloroplast

i Light NADP+ ADP Light Reactions ATP NADPH Chloroplast O2 H2O + P Fig. 10-5-2 H2O Light NADP+ ADP + P i Light Reactions ATP Figure 10.5 An overview of photosynthesis: cooperation of the light reactions and the Calvin cycle NADPH Chloroplast O2

i CO2 Light NADP+ ADP Calvin Cycle Light Reactions ATP NADPH Fig. 10-5-3 H2O CO2 Light NADP+ ADP + P i Calvin Cycle Light Reactions ATP Figure 10.5 An overview of photosynthesis: cooperation of the light reactions and the Calvin cycle NADPH Chloroplast O2

i CO2 Light NADP+ ADP Calvin Cycle Light Reactions ATP NADPH Fig. 10-5-4 H2O CO2 Light NADP+ ADP + P i Calvin Cycle Light Reactions ATP Figure 10.5 An overview of photosynthesis: cooperation of the light reactions and the Calvin cycle NADPH Chloroplast [CH2O] (sugar) O2

Electron transport chain Fig. 10-21 H2O CO2 Light NADP+ ADP + P i Light Reactions: Photosystem II Electron transport chain Photosystem I RuBP 3-Phosphoglycerate Calvin Cycle ATP G3P Figure 10.21 A review of photosynthesis Starch (storage) NADPH Chloroplast O2 Sucrose (export)

Chlorophyll a is the main photosynthetic pigment Accessory pigments, such as chlorophyll b, broaden the spectrum used for photosynthesis Accessory pigments called carotenoids absorb excessive light that would damage chlorophyll Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

RESULTS Fig. 10-9 Chloro- Chlorophyll b Absorption of light by phyll a Chlorophyll b Absorption of light by chloroplast pigments Carotenoids (a) Absorption spectra 400 500 600 700 Wavelength of light (nm) (measured by O2 release) Rate of photosynthesis Figure 10.9 Which wavelengths of light are most effective in driving photosynthesis? (b) Action spectrum Aerobic bacteria Filament of alga (c) Engelmann’s experiment 400 500 600 700

There are two types of photosystems in the thylakoid membrane Photosystem II (PS II) functions first (the numbers reflect order of discovery) and is best at absorbing a wavelength of 680 nm The reaction-center chlorophyll a of PS II is called P680 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Photosystem I (PS I) is best at absorbing a wavelength of 700 nm The reaction-center chlorophyll a of PS I is called P700 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

O2 is released as a by-product of this reaction P680+ (P680 that is missing an electron) is a very strong oxidizing agent H2O is split by enzymes, and the electrons are transferred from the hydrogen atoms to P680+, thus reducing it to P680 O2 is released as a by-product of this reaction Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Calvin Cycle Regenerates starting material Builds sugar from smaller molecules using ATP and NADPH 3 Phases Carbon fixation (uses rubisco) Reduction Regneration of the CO2 acceptor (RuBP)

CAM plants Photosynthetic adaptation to arid conditions Plants open stomata during the night and close during the day (reverse of other plants)

C4 Plants Plants that have an additional step before the Calvin cycle Incorporate CO2 in four-carbon compounds in mesophyll cells

Glycolysis Occurs in the cytoplasm Anaerobic reaction Requires 2 ATP Produces 4 ATP, 2 NADH, and 2 Pyruvate

Kreb Cycle (aka citric acid cycle) Aerobic process Occurs in mitochondria (matrix) Each turn of the cycle generates 1 ATP 3 NADH 1 FADH2 For each glucose molecule, there are 2 turns (total of 2 ATP, 6 NADH, and 2 FADH2)

Electron Transport Chain NADH and FADH2 are electron carriers which donate electrons to the chain which causes the formation of ATP Aerobic Process Cristae of mitochondria and intermembrane space Creates H2O Creates about 32 ATP Uses H+ gradient to drive ATP synthesis

Fig. 10-UN5

i INTERMEMBRANE SPACE H+ Stator Rotor Internal rod Cata- lytic knob Fig. 9-14 INTERMEMBRANE SPACE H+ Stator Rotor Internal rod Figure 9.14 ATP synthase, a molecular mill Cata- lytic knob ADP + P ATP i MITOCHONDRIAL MATRIX

Fermentation Glycolysis plus regeneration of NAD+ (for reuse in glycolysis) Occurs in Cytoplasm Anaerobic respiration Two types Alcohol Lactic acid Does not generate any ATP just electron carrier proteins