3.7/3.8 – Cell respiration & photosynthesis

1. 3.7/3.8 – Cell respiration & photosynthesis Topic 3 – The chemistry of life

4. Cell respiration • Respiration is the controlled release of energy from organic compounds in cells to form ATP • All organisms respire – it is the production of ATP from organic molecules • Aerobic respiration requires oxygen – this is where ventilation and gas exchange come in

6. Glycolysis *Assuming that glucose is the organic nutrient being metabolized, all cells begin the process of cell respiration in the same way In glycolysis the 6C glucose sugar is broken down into two 3C pyruvate Some bonds of the sugar were broken to create a small yield of ATP

7. Anaerobic respiration • Anaerobic respiration occurs in the absence of oxygen • Reactions do not continue in the mitochondria - YEAST: CO2 and ethanol are produced (fermentation) - ANIMALS: lactic acid (lactate) is produced

8. Aerobic respiration • Reactions continue in the mitochondria • Large yield of ATP • Water is a waste product recycled in the cell • CO2 is excreted through gas exchange

12. Aerobic vs anaerobic respiration Similarities Differences Aerobic Uses oxygen High yield of ATP Waste products: CO2/water Pyruvate carried to mitochondria Can metabolize other molecules • Both can start with glucose • Both produce pyruvate (by glycolysis) • Both produce ATP • Both produce CO2 Anaerobic • No oxygen • Low yield of ATP • Waste products: • YEAST: CO2/ethanol • ANIMALS: lactic acid • Occurs in cytoplasm only

13. 3.7/3.8 – Cell respiration & photosynthesis Topic 3 – The chemistry of life

14. Photosynthesis

15. Photosynthesis involves the conversion of light energy into chemical energy Light energy from the sun is composed of a range of wavelengths (colors)

16. The electromagnetic spectrum Only a small part of the electromagnetic spectrum is visible to our eyes. The pigments in photosynthetic organisms (chlorophyll), absorb useful wavelengths of light – those that contain energy appropriate for photolysis in the light-dependent reactions This gives rise to the action and absorption spectra for photosynthesis

18. Do all plants have the same action/absorption spectrum? Why do leaves turn brown in the fall? Some leaves have accessory pigments which cannot normally be seen when chlorophyll is active. When temperatures cool down, chlorophyll breaks down before the accessory pigments, leaving them to show through

19. Light at the blue end of the spectrum contains more energy than light at the red end (though red light is more efficiently absorbed than blue) • UV radiation is higher energy still, but cannot be used. In fact, it causes cell damage and mutations • Artificial light sources could be used (as long as they are within the spectrum), though light intensity if much stronger from the sun

25. Outline the effects of light intensity, temperature and carbon dioxide concentration on the rate of photosynthesis of a green plant. (6 marks)

26. Outline the effects of light intensity, temperature and carbon dioxide concentration on the rate of photosynthesis of a green plant. (6 marks)

27. Think: How would pH affect the rate of photosynthesis of a green plant?

28. Think: How would pH affect the rate of photosynthesis of a green plant?

29. Questions?