Chapter 8 Cellular Energy

2. Chapter 8 Cellular Energy Section 1: How Organisms Obtain Energy Section2: Photosynthesis Section 3: Cellular Respiration

3. Big Idea • Photosynthesis converts the Sun’s energy into chemical energy, while cellular respiration uses chemical energy to carry out life function.

4. Cellular Energy Chapter 8 8.1 How Organisms Obtain Energy All living organisms use energy to carry out all biological processes Macromolecules are assembled and broken down, substances are transported across cell membranes, and genetic instructions are transmitted. All of these cellular activities require energy.

5. 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.

6. Cellular Energy Chapter 8 8.1 How Organisms Obtain Energy Laws of Thermodynamics • First law— (Law of conservation of energy) • energy can be converted from one form to another, but it cannot be created nor destroyed. • Examples: • Food is converted to chemical energy when you eat • Mechanical energy when you run or kick a ball

7. Cellular Energy Chapter 8 8.1 How Organisms Obtain Energy Laws of Thermodynamics • Second law—energy cannot be converted without the loss of usable energy. • “loss” energy is generally converted to thermal energy • Increases Entropy

8. Cellular Energy Chapter 8 8.1 How Organisms Obtain Energy Laws of Thermodynamics • Entropy – • The measure of disorder (or unusable energy) in a system

9. Cellular Energy Chapter 8 8.1 How Organisms Obtain Energy Autotrophs and Heterotrophs • Nearly all the energy for life comes from the Sun

10. Cellular Energy Chapter 8 8.1 How Organisms Obtain Energy Autotrophs and Heterotrophs • Autotrophs are organisms that make their own food.

11. Cellular Energy Chapter 8 8.1 How Organisms Obtain Energy Autotrophs and Heterotrophs • Autotrophs are organisms that make their own food. • Examples: • Chemoautotrophs use inorganic substances such as hydrogen sulfide as a source of energy • Photoautotrophs (like plants) convert light energy from the Sun into chemical energy.

12. Cellular Energy Chapter 8 8.1 How Organisms Obtain Energy Autotrophs and Heterotrophs • Heterotrophs are organisms that need to ingest food to obtain energy. • Examples: • Aphid • Lady bug

13. 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

14. Cellular Energy Chapter 8 8.1 How Organisms Obtain Energy Metabolism • Metabolic Pathway – • Series of chemical reactions in which the product of one reaction is the substrate for the next reaction • Examples: • Catabolic pathways • Anabolic pathways

15. Cellular Energy Chapter 8 8.1 How Organisms Obtain Energy Metabolism • Metabolic Pathway – • Examples: • Catabolic pathways • Release energy by breaking down larger molecules into smaller molecules

16. Cellular Energy Chapter 8 8.1 How Organisms Obtain Energy Metabolism • Metabolic Pathway – • Examples: • Anabolic pathways • Use the energy released by catabolic pathways to build larger molecules from smaller molecules

17. Cellular Energy Chapter 8 8.1 How Organisms Obtain Energy Photosynthesis • Photosynthesis is the anabolic pathway in which light energy from the Sun is converted to chemical energy for use by the cell. • Autotrophs use light energy, carbon dioxide, and water to form glucose and oxygen

18. Cellular Energy Chapter 8 8.1 How Organisms Obtain Energy Cellular Respiration • Cellular Respiration is the catabolic pathway in which organic molecules are broken down to release energy for use by the cell. • Oxygen is used to break down organic molecules, resulting in the production of carbon dioxide and water

19. Cellular Energy Chapter 8 8.1 How Organisms Obtain Energy ATP: The Unit of Cellular Energy • ATP (Adenosine Triphosphate) 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.

20. Cellular Energy Chapter 8 8.1 How Organisms Obtain Energy ATP: The Unit of Cellular Energy • ATP structure • A nucleotide made of an adenine base, a ribose sugar, and three phosphate group

21. Cellular Energy Chapter 8 8.1 How Organisms Obtain Energy ATP: The Unit of Cellular Energy • ATP function • 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

22. Cellular Energy Chapter 8 8.2 Photosynthesis Main Idea: light energy is trapped and converted into chemical energy during photosynthesis • Photo – means “light” • Synthesis – means “to create”

23. Cellular Energy Chapter 8 8.2 Photosynthesis Most autotrophs – including plants – make organic compounds, such as sugars, by a process called photosynthesis

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

25. Cellular Energy Chapter 8 8.2 Photosynthesis Phase One: Light Reactions (Light – Dependent Reaction) • The absorption of light is the first step in photosynthesis. • Light energy is absorbed and then transformed into chemical energy in the form of ATP and NADPH

26. Cellular Energy Chapter 8 8.2 Photosynthesis Phase One: Light Reactions (Light – Dependent Reaction) • Chloroplasts large organelles that capture light energy.

27. Cellular Energy Chapter 8 8.2 Photosynthesis Phase One: Light Reactions (Light – Dependent Reaction) • Chloroplasts are mainly found in the cells of leaves in plants.

28. Cellular Energy Chapter 8 8.2 Photosynthesis Phase One: Light Reactions (Light – Dependent Reaction) • Thylakoids are flattened saclike membranes that arranged in stacks called grana.

29. Cellular Energy Chapter 8 8.2 Photosynthesis Phase One: Light Reactions (Light – Dependent Reaction) • Stroma is the fluid- filled space outside the grana

30. Cellular Energy Chapter 8 8.2 Photosynthesis Phase One: Light Reactions (Light – Dependent Reaction) • Pigments are light-absorbing molecules found in the thylakoid membranes of chloroplasts

31. Cellular Energy Chapter 8 8.2 Photosynthesis Phase One: Light Reactions (Light – Dependent Reaction) • Chlorophyll is the major light – absorbing pigment in plants. • Two types of chlorophyll: • Chlorophyll a • Chlorophyll b • Accessory pigments called carotenoids produce the color of carrots and sweet potatoes

32. 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, H+ into the thylakoid space, and O2 as a waste product.

33. 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.

34. 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.

35. The Light Reaction

36. Light Reactions • kjh

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

39. Cellular Energy Chapter 8 8.2 Photosynthesis Phase Two: The Calvin Cycle (Light – Independent Reaction) • The ATP and NADPH that were formed in phase one are used to make glucose

40. Cellular Energy Chapter 8 8.2 Photosynthesis Phase Two: The Calvin Cycle (Light – Independent Reaction)

41. Cellular Energy Chapter 8 8.2 Photosynthesis • 1st Step (Carbon Fixation) - Six CO2 molecules combine with six 5-carbon compounds to form twelve 3-carbon molecules called 3-PGA. • 2nd Step (Reduction) - The chemical energy stored in ATP and NADPH is transferred to the 3-PGA molecules to form high-energy molecules called (glyceraldehyde 3- phosphate) G3P.

42. Cellular Energy Chapter 8 8.2 Photosynthesis • 3rd Step - Two G3P molecules leave the cycle to be used for the production of glucose and other organic compounds. • Final Step (Regeneration of RuBP)- 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.

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

44. 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.

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

46. Cellular Energy Chapter 8 8.3 Cellular Respiration Glycolysis • Glucose is broken down in the cytoplasm through the process of glycolysis.

48. Cellular Energy Chapter 8 8.3 Cellular Respiration Glycolysis • Two molecules of ATP and two molecules of NADH are formed for each molecule of glucose that is broken down. • Two molecules of ATP are required to start the reactions that will produce energy for the cell

49. Cellular Energy Chapter 8 8.3 Cellular Respiration Glycolysis • 2 phosphate groups are joined to glucose (the 2 Phosphate groups are derived from 2 molecules of ATP) • The 6-Carbon molecule of Glucose is broken into two 3-Carbon compounds • Two Phosphate groups are added and electrons and hydrogen ions (H+) combine with two NAD+ molecules to form NADH molecules • Keep in mind that NAD+ is an electron carrier that is similar to NADP (an electron carrier used during photosynthesis) • The two 3-Carbon compounds are converted into two molecules of pyruvate • At the same time 4 molecules of ATP are produced

50. Cellular Energy Chapter 8 8.3 Cellular Respiration Glycolysis • Glycolysis has a net result of two ATP and two pyruvate.