Photosynthesis vs. Respiration : A Comparison Mark Adame St. Mark’s School of Texas Dallas, Texas

Objectives For students to understand the general pathways of photosynthesis and cellular respiration For students to be able to compare & contrast the biochemical pathways of photosynthesis For students to be able to compare & contrast the structures involved in both pathways

The Transfer of Energy in Living Systems

Organelle Structure Mitochondrion –Outer phospholipid bilayer membrane surrounding an intermembrane space which surrounds a highly folded (cristae) inner membrane –Matrix –DNA, RNA, ribosomes Chloroplast –A double outer phospholipid bilayer membrane that houses a fluid-filled compartment called the stroma –Inner membrane system comprised of discs called thylakoids –DNA, RNA, ribosomes

Thylkoids Grana Stroma Double membrane The Chloroplast

Intermembrane space Inner membrane (cristae) Matrix The Mitochondrion

Organelle Function Mitochondrion –To generate ATP from chemical energy stored in organic molecules Chloroplast –To generate carbohydrates from light energy

An Overview of Cellular Respiration

An Overview of Photosynthesis

Overview of Cellular Respiration & Photosynthesis Glycolysis “Prep-step” Krebs (Citric Acid) Cycle Electron transport chain (ETC or ETS) Light-Dependent Reactions (Cyclic & non-cyclic) drive the electron transport chain Light-Independent Reactions (Calvin Cycle)

Some Biochemical Differences Photosynthesis requires light & only occurs in photoautotrophs Cellular respiration occurs in ALL eukaryotic organisms; both heterotrophs AND photoautotrophs (how else would photoautotrophs break down their sugars?)

Reactants & Products Reactants: –Photosynthesis Water & Oxygen Requires light energy & ATP –Cellular Respiration Organic molecules Products –Photosynthesis Sugars which lead to the production of organic molecules –Cellular Respiration Water & Oxygen Creates ATP for use by the cell

Remember This, Backwards & Forwards!!!

REDOX Reactions –“Have electrons, hydrogen ions will travel” H +  e - 4 e H + “Who” gets the 4 e H + ?

Reactants & Products Photosynthesis Cellular Respiration “Who” gets “who's” e - + H + ?

Electron Flow Cellular Respiration –Glucose (cytoplasm) –Pyruvate & NADH –Acetyl-CoA (Matrix) –NADH & FADH 2 (Matrix) –Electron Transport Chain (inner membrane) –O 2  H 2 O (Matrix) Photosynthesis –H 2 O & photolysis –Photosystem II –Electron Transport Chain (Thylakoid membrane) –Photosystem I –NADPH (Stroma) –CO 2 (Stroma) –Glucose (starch & vacuole)

Building up & Breaking Down

Energy Pathways The products of first set of reactions in photosynthesis (light reactions) are used to generate carbohydrates (energy gained by reactants) The products of first set of reactions in cellular respiration are used to generate energy to create ATP (energy lost from reactants) Photosynthesis is an anabolic pathway Cellular respiration is a catabolic pathway

ATP & Energy For each molecule of glucose broken down in cellular respiration, up to molecules of ATP may be generated For each molecule of glucose generated by photosynthesis 18 ATP are used. –These ATP, however, are generated from light energy

Some Similarities

Chemiosmosis & ETC Electron source Electron Carriers (NADPH, NADH) Electron Transport Chain (Cytochrome) Electron sink Proton gradient across an inner membrane Proton motive force ATP Synthase & ATP Production

ATP Generation

NADPH vs. NADH Both cofactors that transport electrons –NADPH aka nicotinamide adenine dinucleotide phosphate –NADH aka Nicotinamide adenine dinucleotide

Additional Differnces/Similarities? List any additional differnces and/or similarities below

Laboratory 4 Plant Pigments & Photosynthesis Pigment properties Chromatography Light reactions & DPIP reduction –6CO 2 + 6H 2 O --sun--> C 6 H 12 O 6 + 6O 2 Spectrophotometers

Chromatography –Pigment properties –Solvent –Hydrogen-bonding –R f Values

Light Reactions DPIP (2, 6-dicholorophenol -indophenol) replaces NADPH Spectrophotmeter &  in % transmittance

What is expected from the results

Laboratory 5 Cellular Respiration Aerobic Respiration Respirometers & Gas Law C 6 H 12 O 6 + 6O > 6CO 2 + 6H 2 O kcal/mole (or ~34-36 ATP) Germination of seeds

PV = nRT The Concept: Using the gas laws, cellular respiration can be measured in a closed container.

2KOH + CO 2  K 2 CO 3 + H 2 O n is decreasing for CO 2 & increasing for O 2 C 6 H 12 O 6 + 6O 2  6CO 2 + 6H 2 O

Free Response ENERGY QUESTION 1995: –Energy transfer occurs in all cellular activities. For 3 of the following 5 processes involving energy transfer, explain how each functions in the cell and give an example. –Explain how ATP is involved in each example you choose. –1. Cellular movement –2. Active transport –3. Synthesis of molecules –4. Chemiosmosis –5. Fermentation

Free Response CELLULAR RESPIRATION QUESTION 1982: –Describe the similarities and differences between the biochemical pathways of aerobic respiration and photosynthesis in eukaryotic cells. Include in your discussion the major reactions, the end products, and energy transfers.

Various Links Resources/Metabolic_Pathways.html otosynthesis_1.html