Bellwork : What do cells need energy for? Where does this energy come from?

1. Bellwork: What do cells need energy for? Where does this energy come from?

2. Chapter 8: Photosynthesis Section 8.1 – Energy and life

3. What is ATP? • ATP and it’s sister molecule ADP are compounds that play a very important role in providing energy for a cell’s day to day functions.

4. Why is ATP useful? • ATP acts an energy store/source for the cell • Cells can store energy in ATP when they have excess energy • Cells can release energy from ATP when the cell is in need

5. How does ATP release energy? • Cells can release the energy stored in ATP by the controlled breaking of chemical bonds between the second and third phosphate group

6. Difference between ADP and ATP

7. What is the energy used for? • Active transport • Pumping across a cell membrane against a concentration gradient • Powers cell movement • Contraction of muscles – e.g. the heart • Protein synthesis • Various other functions • Producing light in fireflies

8. Why don’t cells stockpile ATP? • Cells only have enough ATP to last a few seconds • Why? It is not an effective store of energy over a long time • Sugars such as glucose are much more effective long term stores of energy • One glucose molecule stores 90 times the energy required to make one ATP molecule • Storing energy as sugar is much more efficient • ATP can be generated as and when it is needed • Transferring energy for specific uses is easier from ATP

9. Where does the energy come from? • Heterotrophs – food • All animals and fungi • Autotrophs – are able to generate their own food • All life on earth depends on Autotrophs • They can harness the sun’s energy and produce carbohydrates • Sugars and starches • Photosynthesis! • Light energy from the sun is converted into chemical energy

10. History of research on photosynthesis • 1643 – Jan Van Helmont notice plants take up water and this contributes to their weight • 1771 - Joesph Priestly used a bell jar, plant and candle to show that plants produce oxygen • 1779 – Jan Ingenhousz showed that aquatic plants produce oxygen bubbles in the light but not the dark • 1845 – Julius Robert first proposed that plants convert light energy into chemical energy • 1948 – Melvin Calvin traces the path of Carbon in the formation of glucose • 1992 – Rudolph Marcus wins Nobel prize for work on electron transport chain • 2004 – So Iwata and Jim Barber describe how water molecules split during photosynthesis