Transformation of Energy

1. Cellular Energy Chapter 8 8.1 How Organisms Obtain Energy Transformation of Energy • Energy is the ability to do work. • Thermodynamics is the study of the flow and transformation of energy in the universe.

2. Cellular Energy Chapter 8 8.1 How Organisms Obtain Energy Laws of Thermodynamics • First law—energy can be converted from one form to another, but it cannot be created nor destroyed. • Second law—energy cannot be converted without the loss of usable energy.

3. Cellular Energy Chapter 8 8.1 How Organisms Obtain Energy Autotrophs and Heterotrophs • Autotrophs are organisms that make their own food. • Heterotrophs are organisms that need to ingest food to obtain energy.

4. Cellular Energy Chapter 8 8.1 How Organisms Obtain Energy Metabolism • All of the chemical reactions in a cell • Photosynthesis—light energy from the Sun is converted to chemical energy for use by the cell • Cellularrespiration—organic molecules are broken down to release energy for use by the cell

5. Cellular Energy Chapter 8 8.1 How Organisms Obtain Energy ATP: The Unit of Cellular Energy (adenosine triphosphate) • ATP releases energy when the bond between the second and third phosphate groups is broken, forming a molecule called adenosine diphosphate (ADP) and a free phosphate group. ATP

6. Cellular Energy Chapter 8 8.2 Photosynthesis Overview of Photosynthesis • Photosynthesis occurs in two phases. • Light-dependent reactions • Light-independent reactions

7. Cellular Energy Chapter 8 8.2 Photosynthesis Phase One: Light Reactions • The absorption of light is the first step in photosynthesis. • Chloroplasts capture light energy.

8. Cellular Energy Chapter 8 8.2 Photosynthesis Electron Transport • Light energy (excites electrons in photosystem II and also) • causes a water molecule to split, releasing an electron into the electron transport system (source of energy for the reactions to occur • H+ (a proton), which helps in the production of ATP • O2 as a waste product (which we kinda like)

9. Cellular Energy Chapter 8 8.2 Photosynthesis • The excited electrons move from photosystem II to an electron-acceptor molecule in the thylakoid membrane. • The electron-acceptor molecule transfers the electrons along a series of electron-carriers to photosystem I.

10. Cellular Energy Chapter 8 8.2 Photosynthesis • Photosystem I transfers the electrons to a protein called ferrodoxin. • Ferrodoxin transfers the electrons to the electron carrier NADP+, forming the energy-storing molecule NADPH.

11. Cellular Energy Chapter 8 8.2 Photosynthesis Phase Two: The Calvin Cycle • In the second phase of photosynthesis, called the Calvin cycle, energy is stored in organic molecules such as glucose.

12. Cellular Energy Chapter 8

13. Cellular Energy Chapter 8 8.2 Photosynthesis • Six CO2 molecules combine with six 5-carbon compounds to form twelve 3-carbon molecules called 3-PGA. • The chemical energy stored in ATP and NADPH is transferred to the 3-PGA molecules to form high-energy molecules called G3P.

14. Cellular Energy Chapter 8 8.2 Photosynthesis • Two G3P molecules leave the cycle to be used for the production of glucose and other organic compounds. • An enzyme called rubisco converts the remaining ten G3P molecules into 5-carbon molecules called RuBP. • These molecules combine with new carbon dioxide molecules to continue the cycle.

15. Cellular Energy Chapter 8 8.2 Photosynthesis Alternative Pathways • C4 plants • CAM plants

16. Light absorbing pigments in plants are found in the thylakoid membranes of chloroplasts There are several kinds of chlorophyll that each absorb a different wavelength of light (why could this be important?) In addition there are other accessory pigments such as carotenoids that absorb light The Importance of Pigments

17. The thylakoid has a stacked structure to allow more surface area and thus a more efficient energy transfer during the electron transport. The folded structure provides the space needed to hold large numbers of electron-transporting molecules AND the protein complexes called PHOTOSYSTEMS (remember them, 1 & 2) The importance of the Thylakoid structure

18. This is the process in which ATP is made in conjunction with electron transport Chemiosmosis is the mechanism by which ATP is produced as a result of the flow of electrons down a concentration gradient Chemiosmosis

19. The water molecule going into electron transport gives its electrons to photosystem II (to make NADP into NADPH) and the H+ (proton) to make ATP (from ADP) SO….

20. Cellular Energy Chapter 8 8.3 Cellular Respiration Overview of Cellular Respiration • Organisms obtain energy in a process called cellular respiration. • The equation for cellular respiration is the opposite of the equation for photosynthesis.

21. Cellular Energy Chapter 8 8.3 Cellular Respiration • Cellular respiration occurs in two main parts. • Glycolysis • Aerobic respiration

22. Anaerobic processes do not require oxygen The first stage of cellular respiration is glycolysis, it is an anaerobic process Aerobic processes require oxygen respiration includes the Krebs cycle and electron transport Anaerobic versus Aerobic

23. Cellular Energy Chapter 8 8.3 Cellular Respiration Glycolysis • Glucose is broken down in the cytoplasm through the process of glycolysis. • Two molecules of ATP and two molecules of NADH are formed for each molecule of glucose that is broken down.

24. Glycolysis (breakdown)

25. Cellular Energy Chapter 8 8.3 Cellular Respiration Krebs Cycle • Glycolysis has a net result of two ATP and two pyruvate. • Most of the energy from the glucose is still contained in the pyruvate. • The series of reactions in which pyruvate is broken down into carbon dioxide is called the Krebs cycle.

26. Is also called: Tricarboxylic acid cycle (TCA) or The Citric Acid Cycle The Krebs Cycle

27. Cellular Energy Chapter 8 8.3 Cellular Respiration • The net yield from the Krebs cycle is six CO2 molecules, two ATP, eight NADH, and two FADH2.

28. Cellular Energy Chapter 8 8.3 Cellular Respiration Electron Transport • Final step in the breakdown of glucose • Point at which ATP is produced • Produces 24 ATP

29. Cellular Energy Chapter 8 8.3 Cellular Respiration Anaerobic Respiration • The anaerobic pathway that follows glycolysis • Two main types • Lactic acid fermentation • Alcohol fermentation Cellular Respiration

30. There are two kinds of fermentation Fermentation is breaking down sugar without oxygen In one type sugar breaks down into lactic acid C6H12O6  2 H+ + 2 C3H5O3- Fermentation

31. This is done by your muscles when the demand for ATP is high, but you are low in oxygen. (while working out) This can cause soreness in the muscles. Lactic Acid Fermentation

32. sugar breaks down into carbon dioxide and ethanol C6H12O6  2 CO2 + 2 C2H5OH Ethanol is the active ingredient in wine, beer and spirits. The Carbon Dioxide produced in this manner can be used to allow bread to rise Alcoholic Fermentation