Energy in Living Systems CH 6 pg 112-118

Organisms classified on how they obtain energy Autotrophs Make their own food from organic molecules Most convert light energy into chemical energy Carbon Dioxide (CO2) and water (H2O) to organic compound Oxygen (O2) released Heterotrophs Cannot make their own food inorganic compounds Eat autotrophs or other heterotrophs

Photosynthesis

Harvesting Light Energy Photosynthetic organisms have chloroplasts Chloroplasts are the organelles that convert light energy into chemical energy. Contains flat, disc-like sacs called thylakoids. this is the first stage of photosynthesis.

Thylakoids

Light Absorption in Chloroplast Sunlight composed of ROY G BIV, different colors. (Lgth = Amt of Engy) Color observed when light strikes an object, waves are reflected, transmitted, or absorbed Colors react depending on the pigment present

Harvesting Light Energy, continued Chlorophyll (a and b) Absorbs blue and red light and reflects green and yellow light Carotenoids help plants absorb additional light energy absorb blue and green light, reflect red, orange and yellow(fall colors)

Two Electron Transport Chains First reaction in photosynthesis is the light reaction takes place in the chlorophyll Light hits a thylakoid Energy is absorbed by the pigment molecules and are directed to a special chlorophyll molecule that acts as a reaction center Electrons are excited and move to other molecules and the electron transport chain. One ETC makes ATP and Second makes NADPH

Understanding Terms Photosystem II (ETC #1) Photosystem I (ETC#2) Products: Electron, Oxygen (pg 117) ATP (pg 118) Photosystem I (ETC#2) Products: NADPH Light Reaction (Electron Transport Chains) create energy molecules for the Calvin Cycle

1st Electron Transport Chain Producing ATP Step 1: An enzyme splits water molecules , e- is released. H+ ions stay within the thylakoid e- is charged by pigment Oxygen gas is released into the atmosphere

Step 2: Carrier Proteins (ATP Synthase) in the membrane pump H+ ions into the thylakoid,

Step 3: Energy diffusion of H+ ions through ATP synthase is used to make ATP

2nd Electron Transport Chain Step 4: Producing NADPH Renergizing, Light excites electrons that are passed on to the second chain.

Step 5: Making NADPH Excited electrons combine with H+ ions and NADP+ to form NADPH. NADPH is used to store energy in organic molecules. (used later in dark reaction)

Electron Transport Chains of Photosynthesis Click to animate the image.

Producing Sugar The first two stages of photosynthesis depend directly on light to make ATP and NADPH. In the final stage of photosynthesis, ATP and NADPH are used to produce energy-storing sugar molecules from the carbon in carbon dioxide. The use of carbon dioxide to make organic compounds is called carbon dioxide fixation, or carbon fixation. (Light Independent, Dark Reaction, or Calvin Cycle)

Calvin Cycle Takes place outside of the Thylakoid in the stroma solution surrounding the thylakoid Carbon Fixation, CO2 is being used to make G3P Enzyme Rubisco adds CO2 to RuBP to create G3P which is later used to make a sugar (Glucose or C6H1206)

What is happening in the Calvin Cycle? This is what you need to know Part 1 Carbon Fixation Carbon dioxide (from the atmosphere) diffuses into the plant cell and enters the stroma of the chloroplast Rubisco (an enzyme) attaches CO2 to RuBP  as a result of this chemical reaction is now known as molecule PGA. Write Rubisco on illustration by carbon fixation

PGA uses the energy molecules (ATP, NADPH) to create G3P Part 2 Reduction PGA uses the energy molecules (ATP, NADPH) to create G3P ETC #1 and #2 (light reaction) create ATP and NADPH Energy is released from the hydrogen and phosphate bonds to drive a reaction creating G3P NADP and ADP are then recycled in the stroma to be used again in the ETC

Rengeneration of Ribulose (RuBP) Step 3 Some of the G3P molecules are then used to make glucose Transported out of the chloroplast Step 4 Other G3P molecules are recycled into making RuBP In order to continue the Calvin Cycle

Factors that Affect Photosynthesis Light intensity (ATP and NADPH) Carbon dioxide concentration Temperature (function of enzymes)

Relationship