Photosynthesis and Cellular RespirationSection 2 Energy in Living Systems CH 6 pg

Photosynthesis and Cellular RespirationSection 2 Organisms classified on how they obtain energy Autotrophs –Make their own food from organic molecules –Most convert light energy into chemical energy Carbon Dioxide (CO 2 ) and water (H 2 O) to organic compound Oxygen (O 2 ) released Heterotrophs –Cannot make their own food inorganic compounds –Eat autotrophs or other heterotrophs

Photosynthesis and Cellular RespirationSection 2 Photosynthesis

Photosynthesis and Cellular RespirationSection 2 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.

Photosynthesis and Cellular RespirationSection 2 Thylakoids

Photosynthesis and Cellular RespirationSection 2 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 Light Absorption in Chloroplast

Photosynthesis and Cellular RespirationSection 2 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)

Photosynthesis and Cellular RespirationSection 2 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

Photosynthesis and Cellular RespirationSection 2 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 1 st Electron Transport Chain

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

Photosynthesis and Cellular RespirationSection 2 Step 3: Energy diffusion of H+ ions through ATP synthase is used to make ATP

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

Photosynthesis and Cellular RespirationSection 2 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)

Photosynthesis and Cellular RespirationSection 2 Electron Transport Chains of Photosynthesis Click to animate the image.

Photosynthesis and Cellular RespirationSection 2 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)

Photosynthesis and Cellular RespirationSection 2

Photosynthesis and Cellular RespirationSection 2 Calvin Cycle Carbon Fixation, an enzyme adds CO 2 to a five carbon molecule (RuBP) Takes place outside of the Thylakoid in the stroma, solution surrounding the thylakoids

Photosynthesis and Cellular RespirationSection 2 Calvin Cycle CO 2 diffuses into the stroma The enzyme (RuBP) adds CO 2 to a five carbon molecule This occurs 3 times to make six carbon molecule 6 carbon molecule splits into 2 – 3 carbon molecules (3 – PGA)

Photosynthesis and Cellular RespirationSection 2 G3P GPAG3P RuPB G3P

Photosynthesis and Cellular RespirationSection 2 Each of 3 – PGA is converted into G3P –G3P is a molecule with additional phosphate and H + that were donated by ATP and NADPH –ADP and NADP are then recycled to the ETC One G3P molecule leaves the Calvin Cycle to be used to make carbohydrates The remaining G3P molecules are recycled back to the enzyme RuBP and reenters the Calvin Cycle

Photosynthesis and Cellular RespirationSection 2 G3P GPAG3P RuPB G3P

Photosynthesis and Cellular RespirationSection 2

Photosynthesis and Cellular RespirationSection 2 Factors that Affect Photosynthesis Light intensity Carbon dioxide concentration Temperature

Photosynthesis and Cellular RespirationSection 2 Relationship