Fig. 9-2 Light energy ECOSYSTEM Photosynthesis in chloroplasts CO 2 + H 2 O Cellular respiration in mitochondria Organic molecules + O 2 ATP powers most cellular work Heat energy ATP

becomes oxidized becomes reduced CELLULAR RESPIRATION PHOTOSYNTHESIS ENERGY + 6 CO H 2 O → C 6 H 12 O O 2 Chapter 9 – Cellular Respiration – occurs in both plants and animals; how is energy obtained from the metabolism of carbohydrates (and in less detail also proteins and fats)? Chapter 10- Photosynthesis – how do plants build energy rich sugar molecules using CO 2, H 2 O and sunlight?

Goals of Cellular Respiration and Photosynthesis:  1) Make Energy storage molecule ATP that can used for cellular work  2)Provide building blocks for important molecules the cell needs

Figure 9.5 An introduction to electron transport chains

Many Important Reactions in Bioenergetics Involve Oxidation –Reduction (Redox or Electron Transfer) Reactions becomes oxidized (loses electron) becomes reduced (gains electron) “OIL RIG” = Oxidation Is Loss of electrons, Reduction Is Gain of electrons

Reactants becomes oxidized becomes reduced Products Methane (reducing agent) Oxygen (oxidizing agent) Carbon dioxideWater Redox reactions release energy when electrons in covalent bonds move closer to more electronegative atoms

Fig. 9-UN4 Dehydrogenase

Enzyme ADP P Substrate Enzyme ATP + Product SYNTHESIS OF ATP USING SUBSTRATE LEVEL PHOSPHORYLATION FORMATION OF ATP VIA ENZYME CATALYZED TRANSFER OF PHOSPHATE TO ADP OCCURS IN GLYCOLYSIS AND KREBS CYCLE LESS EFFICIENT METHOD OF SYNTHESIZING ATP THAN OXIDATIVE PHOSPHORYLATION

Synthesis of ATP by Oxidative Phosphorylation Most efficient method of synthesizing ATP; used in both cellular respiration and photosynthesis

Figure 9.6 An overview of cellular respiration (Layer 3)

Figure 9.8 The energy input and output of glycolysis

Figure 9.18 Pyruvate as a key juncture in catabolism

Figure 9.17a Fermentation

Figure 9.17b Fermentation

Link Reaction and the Kreb’s Cycle

Figure 9.10 Conversion of pyruvate to acetyl CoA, the junction between glycolysis and the Krebs cycle

Figure 9.11 A closer look at the Krebs cycle (Layer 4)

Figure 9.12 A summary of the Krebs cycle

Fig NADH NAD + 2 FADH 2 2 FAD Multiprotein complexes FAD FeS FMN FeS Q  Cyt b   Cyt c 1 Cyt c Cyt a Cyt a 3 IVIV Free energy (G) relative to O 2 (kcal/mol) (from NADH or FADH 2 ) 0 2 H / 2 O2O2 H2OH2O e–e– e–e– e–e–

Fig Protein complex of electron carriers H+H+ H+H+ H+H+ Cyt c Q    VV FADH 2 FAD NAD + NADH (carrying electrons from food) Electron transport chain 2 H / 2 O 2 H2OH2O ADP + P i Chemiosmosis Oxidative phosphorylation H+H+ H+H+ ATP synthase ATP 21

Figure 9.19 The catabolism of various food molecules

Beta Oxidation of Fatty Acids Triacyglyercols are broken down into 2 Carbon Acetyl-CoA molecules and fed into Krebs cycle. Link to Beta Oxidation (Campbells) Link to Beta Oxidation (Campbells) Link to 2 C beta oxidation Link to 2 C beta oxidation Note: A 16 carbon fatty acid would be broken down into 16÷2 = 8 CoA segments.

Figure 10.4 An overview of photosynthesis: cooperation of the light reactions and the Calvin cycle (Layer 3)

Figure 10.6 Why leaves are green: interaction of light with chloroplasts

Figure 10.8 Evidence that chloroplast pigments participate in photosynthesis: absorption and action spectra for photosynthesis in an alga Compare absorption spectrum of chlorophyll a to action spectrum Note photosynthesis is effective at more wavelengths than just those where chlorophyll a has high absorbance Key conclusion: Chlorophyll a and Chlorophyll b are responsible for a significant fraction of light absorption in photosynthesis but not all. Presence of additional pigments insures greater range of visible light wavelengths can be used by plant.

How can you explain the shape of these two graphs that describe the rate of photosynthesis as a function of temperature and light intensity? Answers: 1)Light intensity – this is a saturation curve graph. Initially increases light increases the production of key reaction intermediates in photosynthesis, however eventually the enzymes become saturated and the rate plateaus. 2)Temperature- This is a bell curve. There is an optimum temperature at which the activity of the enzymes that catalyze the reactions of photosynthesis operate most efficiently.

Fig Light Fd Cytochrome complex ADP + i H+H+ ATP P synthase To Calvin Cycle STROMA (low H + concentration) Thylakoid membrane THYLAKOID SPACE (high H + concentration) STROMA (low H + concentration) Photosystem II Photosystem I 4 H + Pq Pc Light NADP + reductase NADP + + H + NADPH +2 H + H2OH2O O2O2 e–e– e–e– 1/21/ OVERVIEW OF LIGHT RXNS WITHIN THE CHLOROPLAST

Pigment molecules Light P680 e–e– Primary acceptor 2 1 e–e– e–e– 2 H + O2O2 + 3 H2OH2O 1/21/2 4 Pq Pc Cytochrome complex Electron transport chain 5 ATP Photosystem I (PS I) Light Primary acceptor e–e– P700 6 Fd Electron transport chain NADP + reductase NADP + + H + NADPH 8 7 e–e– e–e– 6 Fig Photosystem II (PS II)

Fig ATP Photosystem II Photosystem I Primary acceptor Pq Cytochrome complex Fd Pc Primary acceptor Fd NADP + reductase NADPH NADP + + H + CYCLIC PATHWAY – PRODUCES ATP ONLY; NO NADPH ALSO NOTE THAT NO O 2 IS PRODUCED

Fig Light Reactions: Photosystem II Electron transport chain Photosystem I Electron transport chain CO 2 NADP + ADP P i + RuBP 3-Phosphoglycerate Calvin Cycle G3P ATP NADPH Starch (storage) Sucrose (export) Chloroplast Light H2OH2O O2O2 Chloroplast in Mesophyll cells

Figure The Calvin cycle (Layer 3)

Link to McGraw Calvin cycle

H 2 O escapes from stomata on hot, dry days Hot, dry conditions → Stomata close to reduce H 2 O loss. Stomata closed →[CO 2 ] ↓, [O 2 ]↑ O 2 outcompetes CO 2 to bind to Rubisco O 2 is added to RuBP, siphons C out of Calvin cycle H2OH2O

Rubisco can also catalyze the addition of O 2 to PGA with disasterous consequences for plants -Rubisco evolved at time in earth’s history in which atmospheric oxygen concentration was very low -No evolutionary pressure to exclude O 2 - Rubisco binds CO 2 more tightly than O 2, but if [O 2 ] is much higher than [CO 2 ], O 2 will out compete CO 2 for active site; also higher temperatures increase relative affinity for O 2. -Transfer of O 2 ultimately causes loss of carbon, instead of gain of carbon in Calvin cycle

Impact of Photorespiration on Calvin cycle

Figure C 4 and CAM photosynthesis compared Table Link

Mechanisms of Carbon Fixation KEY DIFFERENCE- HOW CO 2 IS CAPTURED