Introduction to PHOTOSYNTHESIS

Cell Energy & Photosynthesis (Chapter 8) All living things require energy to function. Heterotrophs (animals/consumers) get their energy by consuming other living things. Autotrophs (plants) are capable of producing their own food, with the help of chloroplasts and chlorophyll. In all cells, energy from food is stored in the chemical bonds of a molecule called ATP (adenosine triphosphate) Energy is stored in phosphate bonds. Adenosine P

Cell Energy & Photosynthesis When ATP releases a phosphate group, energy is released and ATP becomes ADP (adenosine diphosphate) ADP can reform ATP by bonding with another phosphate group. Adenosine P + P P

Photosynthesis Photosynthesis: the process plants use to trap the sun’s energy and make glucose to store energy. Photosynthesis occurs in 2 phases: 1) Light Dependent Reactions 2) Light Independent Reactions (Calvin Cycle)

PHOTOSYNTHESIS 6CO2 + 6H2O ----Sun Light---> C6H12O6 + 6O2 Occurs in the chloroplast Chlorophyll is the main pigment absorbing the light energy Thylakoid– disklike structure in the chloroplast (think frisbee) Grana- stack of thylakoids (think stack of frisbees) Stroma- open area inside the chloroplast

LIGHT-Dependent REACTIONS 6CO2 + 6H2O ----Sun Light---> C6H12O6 + 6O2 Occurs in the THYLAKOID MEMBRANE of the chloroplast (in the “frisbee”) Water is turned into Oxygen: Photo System II splits water molecules which releases OXYGEN (O2) Light energy is STORED in ATP and NADPH molecules ATP and NADPH go to the stroma (open space of chloroplast) to finish the photosynthesis reaction

CALVIN CYCLE (Light-Independent Reactions) 6CO2 + 6H2O ----Sun Light---> C6H12O6 + 6O2 Occurs in the STROMA (chloroplast’s open space) Carbon Dioxide (CO2) is turned into Glucose (C6H12O6) CO2 combines with other carbon molecules and Rubisco to eventually form GLUCOSE The energy needed to transform the CO2 is released from ATP and NADPH, changing them into ADP+ and NADP+ NO SUNLIGHT IS NEEDED FOR THIS PART!

STROMA GRANUM THYLAKOID C6H12O6 (sugar)

CELLULAR RESPIRATION: the process that releases energy from food using oxygen

CELLULAR RESPIRATION C6H12O6 + 6O2 6CO2 + 6H2O + ENERGY EXACT OPPOSITE of photosynthesis! 3 stages: GLYCOLYSIS (Stage 1) KREB’S CYCLE (Stage 2) ELECTRON TRANSPORT CHAIN (Stage 3) Occurs in MITOCHONDRIA

Mitochondria Structure

Step 1: Glycolysis GLYCOLYSIS: “Glucose Splitting” Occurs without oxygen (anaerobic) In the CYTOPLASM of the cell Glucose is broken down into 2 PYRUVATE molecules 2 ATP are produced

Step 2: Kreb’s (Citric Acid) Cycle KREB’S CYCLE (Citric Acid Cycle) Requires oxygen to function (aerobic) Occurs in the MITOCHONDRIAL MATRIX Pyruvate is broken down into 6 CO2 molecules 2 more ATP are produced

Step 3: Electron Transport Chain Requires oxygen to function Occurs on the inner MITOCHONDRIAL MEMBRANE Electron transport chain pumps H+ ions across membrane to make ATP 6 H2O and 32 ATP produced

_____________ Most Organisms ______________ Yeast

32 ATP H2O O2 CO2 Glycolysis Glucose 2 ATP Electron Transport Chain _____________ Most Organisms Glucose O2 2 ATP Glycolysis Electron Transport Chain Pyruvate Krebs Cycle 32 ATP ______________ Yeast 2 ATP H2O CO2

So… what happens when Oxygen is not available? Start with Glycolysis, and then… Fermentation

Fermentation Anaerobic process used after glycolysis to make more ATP when oxygen is not available Lactic Acid Fermentation (Most organisms) Enzymes convert pyruvate into LACTIC ACID Sore muscles = lactic acid build up Used to produce dairy products Alcohol Fermentation (Microorganisms & Yeast) Enzymes convert pyruvate into ETHYL ALCOHOL and CO2 Occurs in yeast and some bacteria

32 ATP H2O O2 CO2 Glycolysis Glucose 2 ATP Electron Transport Chain _____________ Most Organisms Glucose O2 2 ATP Glycolysis Electron Transport Chain Pyruvate Krebs Cycle 32 ATP ______________ Yeast 2 ATP H2O CO2

32 ATP H2O O2 CO2 Glycolysis Fermentation Glucose 2 ATP Electron _____________ Most Organisms Glucose O2 2 ATP Glycolysis Electron Transport Chain Pyruvate Krebs Cycle Fermentation 32 ATP 2 ATP Lactic Acid ______________ Yeast Alcoholic H2O CO2

Big Picture Photosynthesis removes carbon dioxide from the atmosphere, and respiration puts it back. Photosynthesis puts oxygen into the atmosphere, and respiration uses oxygen to release energy from food.