1. E 2.2 Photosynthesis

2. All life as we know it depends on the process of photosynthesis This is the process by which plants use simple compounds and sunlight in order to make complex substances to build their own bodies Animals then eat these complex substances and use them to build their own bodies

3. Photosynthesis

4. This is essentially the conversion of light energy from the sun into chemical energy The chemical energy is then used to convert CO 2 from the atmosphere to more reduced carbon compounds, primarily sugar This synthesis of sugars by using carbon atoms from CO 2 gas is also called ‘ carbon fixation’ Life on earth depends on the recycling of carbon in this way

5. Carbon cycling https://youtu.be/nzImo8kSXiU Summarise the main points of the video ‘The terrestrial carbon cycle’

6. Greenhouse effect https://youtu.be/3ojaDMadZXU Watch the video on the greenhouse effect and summarise the main points

7. Photosynthetic equations Plants, algae and cyanobacteria use water as a hydrogen donor, releasing O 2 6 CO 2 + 12 H 2 O + light energy  C 6 H 12 O 6 + 6 H 2 O + 6 O 2

8. Photosynthesis Photosynthesis takes place in two stages: Light dependent reactions – Light energy is used to convert ADP and P to ATP. The electron carrier NADP + is reduced to NADPH. The coenzyme NADPH, like NADH is an energy rich carrier of electrons Light-independent reactions – In this second stage the electrons are used along with energy from ATP to reduce CO2 to sugar

9. What is oxidation and reduction? We have been using the terms ‘oxidation’ and ‘reduction’ a lot recently Oxidation is the removal of electrons (e - ) from am atom or a molecule, a reaction that often produces energy In the diagram on the next slide molecule A loses an electron to molecule B. This means that molecule A has undergone oxidation whilst molecule B has undergone reduction Oxidation and reduction molecules are always paired

10. Oxidation-reduction A B A oxidisedB reduced Oxidation

11. The two stages of photostynthesis https://youtu.be/joZ1EsA5_NY Watch the video and summarise the main points

12. The light dependent reactions (photophosphorylation) Photophosphorylation is one of the three ways ATP is formed and it occurs only in photosynthetic cells In this mechanism light energy is absorbed by chlorophyll molecules in the photosynthetic ell, exciting some of the molecules electrons The chlorophyll is located in the membranous thylakoids of chloroplasts The excited electrons jump from the chlorophyll to the first of a series of carrier molecules (an electron transport chain like in respiration)

13. The light dependent reactions As electrons are passed along the series of carriers protons are pumped across the membrane and ADP is converted to ATP by chemiosmosis In non cyclic phosphorylation (used in oxygenic organisms) the electrons released do not return to chlorophyll but are incorporated into NADPH The electrons lost from chlorophyll are replaced by electrons from H 2 O So – the products are ATP, O 2, and NADPH

14. The light-independent reactions The Calvin-Benson cycle These reactions do not require light directly They include a complex cyclic pathway called the Calvin-Benson cycle in which CO 2 is fixed (used to make sugars)

15. How are photosynthesis and respiration related? https://youtu.be/JUmT24R8CyA Watch the video and summarise the main points in your own words