Chapter 8 How Cells Acquire Energy College Prep Biology Mr. Martino

Introduction Autotrophs: (self-nourishing) organisms that make their own food - plants Photosynthesis: capture of sun’s E and conversion of it into food molecules Heterotrophs: (other nourishing) Feed on autotrophs, one another, organic wastes

8.1 Photosynthesis - Overview Chloroplasts: organelles of photosynthesis in plants and algae – produce & storage 2 outer membranes Stroma: thick fluid that surrounds the inner membrane Where sugars are made Thylakoids: disc-like membranous sacs and contain chlorophyll and convert light E Grana: stacks of thylakoids

More Overview Two stages of photosynthesis: 1. Light-dependent Reactions: convert light E into chemical E and release O2 Occurs in the chloroplast Spaces within thylakoids accumulate H+ E from sun drives formation of ATP Water is split and NADP+ picks up e- and H+ = NADPH 2. Light-independent Reactions: (Calvin cycle) assembles sugars using CO2 and products (ATP & NADPH) of light reactions Occurs in stroma ATP provides E NADPH provides e- and H+ CO2 provides C and O atoms

Overview Again 6 CO2 + 12 H2O E C6H12O6 + 6 O2 + 6 H2O Reactants: 12 H2O 6 CO2 Products: 6 O2 C6H12O6 6 H2O

8.2 Sunlight as E Source Photosynthesis is powered by sun Electromagnetic spectrum: radiation E that travels in waves Wavelength: distance between the crests of two adjacent waves - violet short in comparison to red Different pigments absorb different wavelengths Photoautotrophs trap about 1% - visible light Photons: units of light E

More Sunlight as E Chlorophyll a: (key pigment) absorbs mostly blue-violet and red and reflects green – participates directly in light rxns Chlorophyll b: (accessory pigments) absorbs mainly blue and red-orange and reflects yellow-green Carotenoids: (accessory) absorbs blue-violet & blue-green and reflects yellow-orange Flowers, fruits, veggies, leaves Chlorophyll b and carotenoids absorb light and pass it on to chlorophyll a

8.3 Light-Dependent Reactions Three things occur: 1. Pigments absorb light E and excited e- enter the electron transport chain 2. Water molecules are split – ATP & NADPH form while O2 is released 3. Pigments that gave up e- get replacements Photosystems: cluster of proteins and 200-300 pigment molecules in thylakoid Electron Transport System: enzymes, coenzymes and proteins in membrane that transfers e- , trapping E along the way to form ATP and NADPH

8.4 ATP Formation Photolysis: E input causes H2O to split into O2, H+, and e- O2 diffuses out of cell H+ accumulate in thylakoids ETC sends more e- to thylakoids Conc. of H+ becomes greater inside thylakoid than outside – creating both a conc. gradient & electric gradient Sends through ATP synthases into stroma – catalyzing ADP + P = ATP

Light Dependent Reactions Thylakoid membrane Thylakoid space H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ e- e- NAD+ ATP synthase e- e- O H+ H+ NADPH P H+ H+ ADP ATP O2 H+ H+ H+ Stroma H2O NADP O

8.5 Light-Independent Reactions Also called Calvin-Benson Cycle Require E from ATP & H+ & e- from NADPH In stroma, CO2 bonds with enzyme rubisco (RuBP) = unstable 6 C molecule 6 C splits into 2 PGA PGA + P = PGAL Most PGAL form new RuBP 2 PGAL form a glucose Glucose is used to form other carbohydrates ADP & NADP+ diffuse to thylakoids for light rxns

ribulose bisposphate carboxylase Light Dependent Reactions Light Independent Reactions 3 CO2 3 CO2 3 RUBP 6 PGA CO2 6 ATP CO2 Calvin Cycle 3 ATP 5 G3P 6 BPG Thylakoid membrane CO2 Pi 1 G3P 6 G3P 6 NADPH H+ Thylakoid space H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ ribulose bisposphate carboxylase (rubisco) H+ CH2O─ P  H─C─OH H─COOH COOH CH2O─ P  H─C=O H─C─OH NAD+ H+ H+ H+ CH2O─ P  H─C─OH H─COOH COOH CH2O─ P  H─C─OH H─COOH COOH CH2O─ P  H─C=O H─C─OH CH2O─ P  H─C=O H─C─OH ATP H+ NADPH H+ H+ ribulose bisphosphate phosphoglycerate Stroma H2O NADP

Light Dependent Reactions Light Independent Reactions 3 CO2 3 RUBP 6 PGA 6 ATP 6 ATP Calvin Cycle 3 ATP 5 G3P 6 BPG Thylakoid membrane Pi 1 G3P 6 G3P 6 NADPH H+ Thylakoid space H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ CH2O─ P  H─C─OH H─C = O P C = O H+ CH2O─ P  H─C─OH H─COOH COOH NAD+ H+ CH2O─ P  H─C─OH H─C = O P C = O CH2O─ P  H─C─OH H─C = O P C = O H+ H+ CH2O─ P  H─C─OH H─COOH COOH CH2O─ P  H─C─OH H─COOH COOH ATP H+ ATP ATP ATP ATP ATP ATP NADPH ADP ADP ADP ADP ADP ADP H+ H+ Stroma phosphoglycerate bisphosphoglycerate

glyceraldehyde-3-phosphate Light Dependent Reactions Light Independent Reactions 3 CO2 3 RUBP 6 PGA 6 ATP Calvin Cycle 3 ATP 5 G3P 6 BPG Thylakoid membrane Pi 6 NADPH Pi 1 G3P 6 G3P 6 NADH H+ Thylakoid space H+ H+ H+ H+ H+ H+ H  C = O H─C─OH CH2O─ P H+ H+ H+ H+ CH2O─ P  H─C─OH H─C = O P C = O H+ P NAD+ H  C = O H─C─OH CH2O─ P P H  C = O H─C─OH CH2O─ P H  C = O H─C─OH CH2O─ P H+ CH2O─ P  H─C─OH H─C = O P C = O CH2O─ P  H─C─OH H─C = O P C = O H+ H+ ATP H+ P P NADPH NADPH NADPH NADPH NADPH NADPH NADPH H  C = O H─C─OH CH2O─ P P H  C = O H─C─OH CH2O─ P P NADP NADP NADP NADP NADP NADP H+ H+ Stroma glyceraldehyde-3-phosphate (G3P) bisphosphoglycerate

glyceraldehyde-3-phosphate Light Dependent Reactions Light Independent Reactions 3 CO2 3 RUBP 6 PGA 6 ATP Calvin Cycle 3 ATP 5 G3P 6 BPG Thylakoid membrane Pi 1 G3P 6 G3P 6 NADPH H+ Thylakoid space H+ glucose H+ H+ H+ H+ H+ H  C = O H─C─OH CH2O─ P G3P H  C = O H─C─OH CH2O─ P G3P H+ H+ H+ H+ H  C = O H─C─OH CH2O─ P H+ NAD+ H  C = O H─C─OH CH2O─ P H  C = O H─C─OH CH2O─ P H  C = O H─C─OH CH2O─ P H+ H+ H+ ATP H+ NADPH H  C = O H─C─OH CH2O─ P H  C = O H─C─OH CH2O─ P H+ H+ Stroma glyceraldehyde-3-phosphate (G3P)

glyceraldehyde-3-phosphate Light Dependent Reactions Light Independent Reactions 3 CO2 3 RUBP 5 G3P 3 ATP 3 RUBP 6 PGA 6 ATP Calvin Cycle 3 ATP 5 G3P 6 BPG Thylakoid membrane Pi 1 G3P 6 G3P 6 NADPH H+ Thylakoid space H+ glucose H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ CH2O─ P  H─C=O H─C─OH NAD+ H  C = O H─C─OH CH2O─ P H  C = O H─C─OH CH2O─ P H+ H  C = O H─C─OH CH2O─ P H+ H+ CH2O─ P  H─C=O H─C─OH CH2O─ P  H─C=O H─C─OH ATP H+ ATP ATP ATP NADPH H  C = O H─C─OH CH2O─ P H  C = O H─C─OH CH2O─ P H+ ADP ADP ADP H+ Stroma glyceraldehyde-3-phosphate (G3P) Ribulose bisphosphate

8.6 Carbon Fixation Carbon Fixation: incorporating C from CO2 into organic compound Various types of plants adapted for various climates do this at different times to avoid excess water loss