Chapter 8 Cellular Energy

1. Chapter 8 Cellular Energy 8.1 How Organisms Obtain Energy

2. 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.

3. 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.

4. 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.

5. 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

6. Cells need energy for: • Making new molecules • Maintaining homeostasis • Active transport • Endocytosis • Exocytosis • Going against the concentration gradient • Movement • Cilia and flagella • Muscle contraction including cardiac muscle • Cell division

7. ATP stores energy in chemical bonds • A= adenosine • T= tri • P= phosphate

8. ATP and ADP recycle

10. ATP is like currency • Cells can only use the ATP for energy even though they store energy as fats, carbohydrates or proteins • Carbohydrates, fats and proteins must be changed to ATP before they can be used by the cell (process of cellular respiration) • You can only use coins in the soda machine even though you may have a $5 bill in your pocket

11. How cells tap into the energy stored in ATP • Many enzymes have a site where ATP fits in like a battery to provide the energy for that enzyme to work

12. Chapter 8 Cellular Energy 8.2 Photosynthesis

13. Plants change solar energy (sunlight) into ATP then into glucose (chemical energy) Two step process Photosynthesis: The Big Picture

14. Overall reaction of photosynthesis

15. Role of Chloroplasts • Chlorophyll is the pigment found in the chloroplasts of plants and algae • Chloroplast is the location for photosynthesis

16. Thylakoid membrane is the site for photosynthesis Chloroplast Structure

17. Chlorophyll • Plants have two types of chlorophyll • Chlorophyll a is yellow green • Chlorophyll b is blue green • We see plants as green because green is reflected not absorbed by the chlorophyll • Plants also contain red, orange and yellow pigments • When leaves “turn colors” in the fall it is because chlorophyll productions ceases and the other colors are exposed

20. Photosynthesis: A Two Step Process • Step One: Light Dependent Reactions • Step Two: Light Independent Reactions (previously called the Dark Reactions or the Calvin Cycle)

21. Light Dependent Reactions of Photosynthesis • Light strikes a chlorophyll molecule and excites an electron • Electron gets passed to a series of proteins in an electron transport chain and an ATP gets made • Electron goes to a second electron transport chain and another energy molecule (NADPH) gets made

22. Light Dependent Reactions of Photosynthesis • Photolysis must happen to “fill in the hole” left by the electron that was excited • Photolysis is the splitting of water; the hydrogen goes to fill the electron’s place and the oxygen is what we breathe (O2)

23. Light Dependent Reactions of Photosynthesis • Start with sunlight and get ATP and NADPH • Energy molecules used for Step Two • Start with water and get oxygen

24. Light Independent Reactions of Photosynthesis Light dependent Light dependent Light independent

25. Light Independent Reactions of Photosynthesis • ATP and NADPH from the light dependent reaction provide the energy to convert CO2 to C6H12O6 (glucose) • Uses many enzymes in a cycle to produce glucose • Cycles are important in organisms because they allow for constant production

26. Light Independent Reactions of Photosynthesis

27. Light Independent Reactions of Photosynthesis • Each “turn” of the cycle produces ½ of a glucose • ATP and NADPH are used to produce this glucose • No sunlight is needed, reactions happen independent of light

28. Alternative Pathways • C4 Plants: fix CO2 into four-carbon compounds keep stomata closed during hot days (less transpiration water loss) Sugar cane and corn

29. Alternative Pathways • CAM plants: conserve water by allowing CO2 to enter only at night (stomata closed during day to conserve water) • Examples: pineapple, cacti, orchids and other desert or salt march plants

30. Chapter 8 Cellular Energy 8.3 Cellular Respiration

31. Cellular Respiration • Process of breaking down food to produce ATP • ALL living things do cellular respiration, even: • Plants • Bacteria • Eukaryotes in the mitochondria • Prokaryotes in the cytoplasm

32. Cellular Respiration Overall reaction C6H12O6 + O2 CO2 + H2O + energy

33. Cellular Respiration • Three Stage Process • Glycolysis: anaerobic • Citric Acid Cycle: aerobic • Electron Transport Chain: aerobic

34. Cellular Respiration Overview

35. Glycolysis • Happens in the cytoplasm • Need to use two ATP before can get ATP out of the process • One glucose is split and converted into two pyruvate yields four ATP (two net ATP)

36. Citric Acid Cycle or Krebs Cycle • Happens in the mitochondrial matrix • CO2 produced • Per turn of the cycle yields: • 1 ATP • 3 NAPH • 1FADH2

37. Electron Transport Chain

38. Electron Transport Chain • Located within the inner mitochondrial membrane • Converts NADH and FADH2 into ATP • Energized electrons are passed along a series of proteins • Some energy is converted directly into ATP • Other energy causes H+ ions to be forced out of the inner mitochondrial matrix

39. Electron Transport Chain cont. • The force of H+ ions back into the mitochondrial matrix through the enzyme ATP synthase provides the energy for ATP synthesis • Oxygen is the final electron acceptor • Without oxygen the transport chain would shut down like a traffic jam • Traffic (electrons) would back up and shut down the Krebs Cycle as well

40. Electron Transport Chain cont. • For every NADH get 3 ATP • For every FADH2 get 2 ATP • Overall get a net of 32 ATP from one molecule of glucose • Balanced equation: C6H12O6 + 6O2 6CO2 + 6H2O + 32 ATP

41. Fermentation • Occurs when O2 is not present, no aerobic respiration, no Krebs Cycle, no Electron Transport Chain • Allows the continuation of glycolysis by the removal of pyruvate • Some organisms in anaerobic environments produce energy by fermentation all the time

42. Alcoholic Yeast Produce CO2, ethyl alcohol and 2 ATP from pyruvate Important in bread and alcoholic beverage industries Lactic Acid Animal muscle cells, some bacteria and some plants Produce lactic acid and 2 ATP from pyruvate Get sore, burning muscles Liver converts lactic acid back to pyruvate when O2 is present Fermentation: Two Types

43. Comparing Photosynthesis and Cellular Respiration • Both use electron transport chains • Both use cycles of chemical reactions • Both use electron carrier proteins • Both use concentration gradient of H+ ions

44. Photosynthesis Food accumulated Solar energy stored in glucose CO2 taken in, O2 given off Occurs only in presence of chlorophyll with sunlight Cellular Respiration Food broken down Glucose energy released O2 taken in, CO2 given off Occurs in all living things all the time Comparing Photosynthesis and Cellular Respiration