1. Chapter 8
Cellular Energy

2. How Organisms Obtain Energy
Section 1
How Organisms Obtain Energy

3. Section 1: How Organisms Obtain Energy
All living organisms use energy to carry out all biological processes. K
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4. Transformation of Energy
Cellular processes require energy – the ability to do work.
Thermodynamics is the study of the flow and transformation of energy in the universe.
How Organisms Obtain Energy

5. Transformation of Energy
Laws of thermodynamics
First law—the law of conservation of energy: 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, that is, entropy—disorder or unusable energy--increases.
How Organisms Obtain Energy

6. Transformation of Energy
Autotrophs and Heterotrophs
Directly or indirectly, nearly all the energy for life comes from the Sun.
Autotrophs make their own food, either with energy from the sun or from inorganic substances.
Heterotrophs ingest other organisms to obtain energy.
How Organisms Obtain Energy

7. Metabolism
All of the chemical reactions in a cell are referred to as the cell’s metabolism.
A series of chemical reactions in which the product of one is the substrate for the next is called a metabolic pathway.
Catabolic pathways release energy by breaking down larger molecules.
Anabolic pathways use energy to build larger molecules.
How Organisms Obtain Energy

8. Metabolism
Photosynthesis – anabolic pathway in which light energy from the Sun is converted to chemical energy for use by the cell
Cellular respiration – catabolic pathway in which organic molecules are broken down to release energy for use by the cell
How Organisms Obtain Energy

9. ATP: The Unit of Cellular Energy
In living things, chemical energy is stored in biological molecules.
Adenosine triphosphate (ATP) is the most important biological molecule that provides chemical energy.
How Organisms Obtain Energy

10. ATP Crash Course

11. ATP: The Unit of Cellular Energy
ATP structure
Most abundant energy-carrier in cells
Nucleotide made of an adenine base, a ribose sugar, and three phosphate groups
How Organisms Obtain Energy

12. ATP: The Unit of Cellular Energy
ATP function
Releases energy when the bond between the second and third phosphate groups is broken.
Transforms into a molecule called adenosine diphosphate (ADP) and a free phosphate group.
How Organisms Obtain Energy

13. ATP When chlorophyll absorbs light, it is absorbing energy
It stores it in the __________ of Adenosine Triphosphate (ATP)
bonds

14. ATP, continued. Carbs are most commonly broken down to make ATP.
Breakdown of glucose yields 36 ATP.
ATP = Energy currency of the cell.
Cells use ATP for functions such as building molecules & moving materials by Active Transport.
ATP releases energy when phosphate group released.
Becomes Adenosine DiPhosphate (ADP).
Can be converted back to ATP by adding phosphate.

15. ATP vs. ADP

16. ATP ADP Cycle

17. Video
ATP

18. Essential Questions What are the two laws of thermodynamics?
What is the difference between an anabolic pathway and a catabolic pathway?
How does ATP work in a cell?
How Organisms Obtain Energy

19. Section 2
Photosynthesis

20. Section 2: Photosynthesis
Light energy is trapped and converted into chemical energy during photosynthesis. K
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21. Crash Course: Photosynthesis

22. Overview of Photosynthesis
Most autotrophs make organic compounds using photosynthesis.
Photosynthesis is the process of converting light energy into chemical energy.
Photosynthesis

24. THE FORMULA, continued.

25. Overview of Photosynthesis
Photosynthesis occurs in two phases.
In the light-dependent phase, light energy is converted into chemical energy.
In the light-independent phase, chemical energy used to synthesize glucose.
Photosynthesis

26. Bill Nye: Photosynthesis

27. Phase One: Light Reactions
The absorption of light is the first step in photosynthesis.
Once light energy is captured, it can be stored as ATP or NAPDH.
Photosynthesis

28. Phase One: Light Reactions
Chloroplasts
Are organelles that capture light energy
Contain two main compartments:
Thylakoids: flattened saclike membranes
Stacks of thylakoids are called grana.
The fluid filled space outside the grana called the stroma
Photosynthesis

29. Chloroplast structure

30. Phase One: Light Reactions
Pigments
Light-absorbing colored molecules called pigments are found in the thylakoid membranes.
Different pigments absorb specific wavelengths of light.
Most common pigment in plants is chlorophyll.
Plants also have accessory pigments.
Photosynthesis

31. Video
Chlorophyll Borophyll

32. Phase One: Light Reactions
Electron transport
The thylakoid membrane has a large surface area, providing space for a large number of electron transporting molecules and two types of protein complexes called photosystems.
Photosystems house the light-capturing pigments.
Photosynthesis

33. Phase One: Light Reactions
Electron transport
Light energy excites electrons in photosystem II.
This light energy causes a water molecule to split – releasing an electron into the electron transport system, a hydrogen ion (H+ or proton) into the thylakoid space, and oxygen as a waste product.
Photosynthesis

34. Phase One: Light Reactions
Electron transport
The activated electrons move from photosystem II to an acceptor molecule in the thylakoid membrane.
The electron acceptor molecule transfers the electrons along a series of electron carriers to photosystem I.
Photosynthesis

35. Phase One: Light Reactions
Electron transport
In the presence of light, photosystem I transfers the electrons to a protein.
The protein transfers the electrons to the carrier molecule NADP+, forming the energy storage molecule NADPH.
Photosynthesis

36. Phase One: Light Reactions
Electron transport
ATP is produced in conjunction with the electron transport system through chemiosmosis
ATP is produced through the flow of electrons down a concentration gradient
The breakdown of water provides the necessary protons for ATP synthesis
Photosynthesis

37. Phase Two: The Calvin Cycle (light independent reactions)
In the second phase of photosynthesis, called the Calvin cycle, energy is stored in organic molecules such as glucose.
Photosynthesis

38. Phase Two: The Calvin Cycle
The first step of the Calvin cycle is called carbon fixation.
CO2 molecules combine with 5-carbon molecules to form 3- phosphoglycerate (3-PGA)
Photosynthesis

39. Phase Two: The Calvin Cycle
In the second step, chemical energy stored in ATP and NADPH is transferred to the 3-PGA to form glyceraldehyde 3-phospate (G3P).
Photosynthesis

40. Phase Two: The Calvin Cycle
In the third step, some G3P molecules leave the cycle to be used for the production of glucose and other organic compounds.
Photosynthesis

41. Phase Two: The Calvin Cycle
In the fourth and final step, an enzyme called rubisco converts the remaining G3P molecules into 5-carbon molecules called ribulose 1,5-bisphospates (RuBP).
These molecules combine with new CO2 and continue the cycle.
Photosynthesis

42. 2 Main steps of PS - Summary
Light reactions—occurs only in the presence of ___________
Occurs in the grana (thylakoids) of the chloroplasts
Also known as Photolysis because light is used to __________ _________ molecules into hydrogen and oxygen
light
split water

43. 2 Main steps of PS - Summary
2. Dark Reactions—can occur in light ____ darkness. Follows light reactions
Occurs in the stroma of the chloroplasts
Also known as Carbon fixation because CO2 will get “fixed up” with the hydrogens and energy from the light reaction or

45. Light Reactions Take place within the membrane of the thylakoid.
Chlorophyll absorbs energy from sunlight.
Water is __________ _________
Oxygen is ______________
Oxygen leaves the plant and goes into the air
broken down
released
AKA Light-Dependent Reactions.
-Capture energy from sunlight.
-Water & sunlight needed.

46. The Dark Reactions Occur in stroma of chloroplasts.
_________ is added to a cycle of reactions to build larger molecules
A molecule of simple sugar is formed
_____________
CO2
-AKA Light-independent reactions.
-Use energy from the light reactions to make sugars.
-Carbon dioxide needed.
glucose

48. Video
Summary of Photosynthesis

49. Alternative Pathways C4 plants
The C4 pathway allows plants to maintain photosynthesis while reducing water loss.
Significant structural modification in the arrangement of cells within the leaves – separate CO2 uptake from location of Calvin cycle
Photosynthesis

50. Alternative Pathways CAM plants
Crassulacean acid metabolism (CAM) is found in desert plants.
Collect CO2 at night and store it in organic compounds
During the day, release CO2 from organic compounds for the light-dependent cycle of photosynthesis
Photosynthesis

51. Bozeman Science: Photosynthesis

52. Essential Questions What are the two phases of photosynthesis?
What is the function of a chloroplast during the light reactions?
How can electron transport be described and diagramed?
Photosynthesis

53. Section 3
Cellular Respiration

54. Section 3: Cellular Respiration
Living organisms obtain energy by breaking down organic molecules during cellular respiration. K
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55. Crash Course: Cellular Respiration

56. Overview of Cellular Respiration
Organisms obtain energy in a process called cellular respiration.
Respiration harvests electrons from organic molecules and uses the energy to make ATP.
The equation for cellular respiration is the opposite of the equation for photosynthesis:
Cellular Respiration

57. Overview of Cellular Respiration
Cellular respiration occurs in two main parts: glycolysis and aerobic respiration.
Glycolysis is an anaerobic process, meaning it does not require oxygen.
Aerobic respiration involves the Krebs cycle and electron transport.
Aerobic processes require oxygen.
Cellular Respiration

58. 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.
Cellular Respiration

59. Khan Academy: Glycolysis

60. 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.
In the presence of oxygen, pyruvate is transported into the mitochondrial matrix, where it is converted into carbon dioxide.
The series of reactions in which pyruvate is broken down into carbon dioxide is the Krebs cycle, also know as the tricarboxylic acid (TCA) cycle
Cellular Respiration

61. Krebs Cycle Steps of the Krebs cycle
Prior to the Krebs cycle, pyruvate reacts with coenzyme A (CoA) to form acetyl CoA.
Acetyl CoA moves into the mitochondrial matrix.
Acetyl CoA combines with a 4-carbon compound to form citric acid.
Cellular Respiration

62. Krebs Cycle Steps of the Krebs cycle
Citric acid is broken down releasing two molecules of carbon dioxide and generating one ATP, three NADH, and one FADH2.
Finally, acetyl CoA and citric acid are generated and the cycle continues.
Cellular Respiration

63. Steps of Kreb’s Pyruvate broken down Coenzyme A Citric acid formed
Citric acid broken down
5-carbon molecule broken down
4-carbon molecule rearranged
Up to 38 ATP molecules are made from the breakdown of 1 glucose molecule.

65. Khan Academy: Kreb Cycle

66. Video
Kreb's cycle

67. Electron Transport
In aerobic respiration, electron transport is the final step in the breakdown of glucose.
NADH and FADH2 from the Krebs cycle are used to convert ADP to ATP.
Electron transport and chemiosmosis in aerobic respiration are similar to the processes of photosynthesis.
Cellular Respiration

68. Electron Transport Prokaryotic cellular respiration
Some prokaryotes undergo aerobic respiration.
They do not have mitochondria, so they use the cellular membrane as the location of electron transport.
Cellular Respiration

69. Steps of ETC - Summary
Electrons removed – High energy electrons from NADH & FADH2.
Hydrogen ions transported – High energy electrons travel through the proteins in the ETC.
ATP Produced – ATP synthase adds phosphate groups to ADP to make ATP. For each pair of electrons that passes through the ETC, 3 ATPs are made.
Water formed – Oxygen enters cellular respiration process & picks up electrons & hydrogen ions to form water.

70. Khan Academy: ETC

71. Anaerobic Respiration
When oxygen is unavailable, cells cannot follow glycolysis with the aerobic respiration (Krebs cycle and electron transport).
The anaerobic process that follows glycolysis is anaerobic respiration, or fermentation.
Fermentation occurs in the cytoplasm of the cell, and produces NAD+ and ATP.
Cellular Respiration

72. Fermentation Two types _______________ fermentation
Alcoholic
Lactic acid

73. Anaerobic Respiration
Lactic acid fermentation
Enzymes convert the pyruvate made during glycolysis into lactic acid.
Skeletal muscles produce lactic acid when the body cannot supply enough oxygen, such as during periods of strenuous exercise.
Cellular Respiration

74. Anaerobic Respiration
Alcohol fermentation
Occurs in yeast and some bacteria
Converts pyruvate into ethyl alcohol and carbon dioxide
Cellular Respiration

75. Photosynthesis & Cellular Respiration
Organelle for process
Chloroplast
Mitochondrion
Reactants
CO2 & H2O
Sugars (C6H12O6) & O2
Electron Transport Chain
Proteins within thylakoid membrane
Proteins within inner mitochondrial membrane
Cycle of chemical reactions
Calvin cycle in stroma of chloroplasts builds sugar molecules
Krebs cycle in matrix of mitochondria breaks down carbon-based molecules
Equation
6CO2 + 6H2O C6H12O6 + 6O2
C6H12O6 + 6O CO2 + 6H2O
Products

76. Photosynthesis and Cellular Respiration

77. Bozeman Science: Cellular Respiration

78. Essential Questions What are the stages of cellular respiration?
What is the role of electron carriers in each stage of cellular respiration?
What are the similarities between alcoholic fermentation and lactic acid fermentation?
Cellular Respiration