Energy and ATP

2. Energy and ATP • Life depends on energy but where does this energy come from? • Energy is stored in the chemical bonds of molecules. • These molecules release energy when their chemical bonds are broken. • Compounds that store energy include: ATP, NADH, NADPH.

3. The principal chemical compound used by the cell to store and release energy is ATP • ATP – adenosine triphosphate ADP – adenosine diphosphate • ATP is the ultimate storage compound (energy currency of the cell)  • ATP is made of three parts: • ribose • adenine • Three phosphate groups • (adenine + ribose = adenosine)

4. ATP is not good for long term energy storage (glucose stores 90 times more energy) • The cell only keeps a small supply of ATP around – can regenerate ATP from ADP as needed

5. An ATP molecule releases chemical energy whenever a bond holding a phosphate group to the molecule is broken. This creates a new molecule ADP (adenosine diphosphate). • The energy released by converting ATP into ADP can be used by cells to do work. • Cells generate a continuous supply of ATP by attaching a phosphate group to ADP.

6. Photosynthesis is plants converting sunlight energy into the chemical bonds of glucose using CO2 (carbon dioxide) and releasing O2 (oxygen) photo = light synthesis = to build • 6CO2 + 6H2O light and chlorophyll C6H12O6 + 6O2

7. Photosynthesis - the process by which autotrophs convert sunlight into a usable form of energy (FOOD!) • Pigmentis a light absorbing substance (colored substance that absorbs some wavelengths of light and reflect other wavelengths – color you see is the color being reflected) • Autotrophs that perform photosynthesis require pigments to trap the energy in light. The most common pigment in plants is chlorophyll (a and b) but other pigments present but masked by the chlorophyll

8. Chlorophyll is a green pigment that absorbs violet, blue and red wavelengths of light and reflects green and yellow wavelengths of light (why the plant looks green) These wavelengths of light are necessary for photosynthesis. • Autotrophs also contain other pigments called accessory pigments (red, yellow and gold).

9. Structure of the Chloroplast • In many organisms chlorophyll and other pigments are located in specialized organelles inside the cell. These are called chloroplasts. • A photosynthetic cell may contain several thousand chloroplasts. Inside this tiny organelle is where photosynthesis takes place. • Inside the chloroplasts are stacks of disk shaped structures called grana. The individual disk shaped structures are called thylakoids.

10. Structure of the Chloroplast cont. • Chlorophyll is housed inside of the thylakoids along its membrane • chlorophyll is surrounded by the photosynthetic membrane • Inside the thylakoids hundreds of chlorophyll molecules and other pigments are organized into units (clusters) called photosystems. • The region outside the thylakoid membrane is called stroma

11. Photosynthesis has two parts: the light dependent reactions and the light independent reactions • Light dependent reactions take place in the thylakoid membrane • Light independent reactions take place in the stroma • The cell uses electron carriers to transport (transfer) high energy electrons from chlorophyll to other molecules • The compounds that can accept the high energy electrons and pass them with most of their energy to another molecules are called carrier molecules (ex. NADP+ to NADPH and ADP to ATP)

12. Light dependent reactions • requires sunlight – only happens in the daytime • uses sunlight to make ATP, NADPH and oxygen

13. Light dependent reactions cont. • light absorption • light energy absorbed by electrons in chlorophyll that are passed on to electron transport chain 2. electron transport • occurs only in thylakoid membrane • electrons move along membrane • allows transport of H+ ions from the stroma into inner thylakoid space • pigment use light energy and H+ ions to regenerate NADPH from NADP+

14. Light dependent reactions cont. 3. oxygen production • as chlorophyll loses electrons there is a process to replace them in the thylakoid membrane • new electrons (replacement) come from water • enzymes on membrane inner surface break H2O into H+ ions, electrons and oxygen • the oxygen is released into the air 4. ATP formation • The H+ ions formed when water breaks down eventually create areas of unequal charge (+ charge inside and – charge outside) • Protein (called ATP synthase) spans the membrane and allows H+ ions to pass through • As H+ passes through ATP synthase rotates and binds ADP and a phosphate group to form ATP

15. Summary ***Light dependent reactions • use H2O (water), ADP and NADP+ • produce O2 (oxygen), ATP and NADPH

16. Light independent reactions (Calvin Cycle) • sunlight not required for reaction to occur but can occur during the day and will also occur at night • a series of reactions in a non-ending cycle • takes a simple inorganic molecule (CO2) and produces complex organic molecules (glucose) 4. compounds can be removed from the cycle to supply the raw materials the cell needs to make everything the plant needs to function

17. Light independent reactions (Calvin Cycle) cont. 5. a 5-carbon sugar plus CO2 will yield two 3-carbon compounds 6. since 6CO2 are used you then will need six 5-carbon compounds 7. creates a total of twelve 3-carbon compounds 8. two of the 3-carbon compounds are removed from the cycle to produce the materials including glucose that the plant needs to function 9. the remaining ten 3-carbon compounds convert back into six 5-carbon compounds to start the process over

18. Summary • Calvin Cycle • uses CO2 to produce C6H12O6 (glucose) and other compounds the cell needs • the cycle is slow so the enzyme rubisco is needed to speed it up • The Sun’s energy ultimately stored in the bonds of the glucose molecule (a high-energy sugar)

19. The Big Picture • The process of photosynthesis can be summed up by the following chemical equation: • 6CO2 + 6H2O+ energy C6H12O6 + 6O2 • In this equation the sugar glucose is a product. The energy stored in glucose can be used later to produce ATP.

20. Why?? • Plants use glucose for growth; they create molecules such as cellulose by linking chains of glucose molecules.  • Most plants store glucose as starch. Starches are found in plant foods such as wheat and potatoes. • When heterotrophs consume autotrophs they breakdown starches into glucose and use the energy in glucose for their own energy and structural needs.