Energy in Living Systems

1. Energy in Living Systems CH 6 pg 112-118

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 (CO2) and water (H2O) to organic compound • Oxygen (O2) released • Heterotrophs • Cannot make their own food inorganic compounds • Eat autotrophs or other heterotrophs

3. Photosynthesis

4. 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.

5. Thylakoids

6. 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

7. 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(fallcolors)

8. 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

9. 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

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

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

12. 2nd Electron Transport Chain Step 4:Producing NADPH • Renergizing, Light excites electrons that are passed on to the second chain.

13. 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)

14. Electron Transport Chains of Photosynthesis Click to animate the image.

15. 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)

17. Calvin Cycle • Carbon Fixation, an enzyme adds CO2 to a five carbon molecule (RuBP) • Takes place outside of the Thylakoid in the stroma, solution surrounding the thylakoids

18. Calvin Cycle • CO2 diffuses into the stroma • The enzyme (RuBP) adds CO2 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)

19. RuPB G3P GPA G3P G3P

20. 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

21. RuPB G3P GPA G3P G3P

23. Factors that Affect Photosynthesis • Light intensity • Carbon dioxide concentration • Temperature

24. Relationship