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Chapter 8 Cellular Energy. Section 1 How Organisms Obtain Energy.

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Presentation on theme: "Chapter 8 Cellular Energy. Section 1 How Organisms Obtain Energy."— Presentation transcript:

1 Chapter 8 Cellular Energy

2 Section 1 How Organisms Obtain Energy

3 All living organisms use energy to carry out all biological processes. Section 1: How Organisms Obtain Energy K What I Know W What I Want to Find Out L What I Learned

4 How Organisms Obtain Energy 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.

5 How Organisms Obtain Energy 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.

6 How Organisms Obtain Energy 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.

7 How Organisms Obtain Energy 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.

8 How Organisms Obtain Energy 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

9 How Organisms Obtain Energy 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.

10 ATP Crash Course 00jbG_cfGuQ

11 How Organisms Obtain Energy 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

12 How Organisms Obtain Energy 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.

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 Light energy is trapped and converted into chemical energy during photosynthesis. Section 2: Photosynthesis K What I Know W What I Want to Find Out L What I Learned

21 Crash Course: Photosynthesis sQK3Yr4Sc_k

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



25 Photosynthesis 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.

26 Bill Nye: Photosynthesis pdgkuT12e14

27 Photosynthesis 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.

28 Photosynthesis 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

29 Chloroplast structure

30 Photosynthesis 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.

31 Video Chlorophyll Borophyll

32 Photosynthesis 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.

33 Photosynthesis 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.

34 Photosynthesis 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.

35 Photosynthesis 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.

36 Photosynthesis 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

37 Photosynthesis 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.

38 Photosynthesis Phase Two: The Calvin Cycle The first step of the Calvin cycle is called carbon fixation. CO 2 molecules combine with 5-carbon molecules to form 3- phosphoglycerate (3-PGA)

39 Photosynthesis 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).

40 Photosynthesis 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.

41 Photosynthesis 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 CO 2 and continue the cycle.

42 2 Main steps of PS - Summary 1.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 CO 2 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. 1.Chlorophyll absorbs energy from sunlight. – Water is __________ _________ – Oxygen is ______________ 2.Oxygen leaves the plant and goes into the air broken down released

46 The Dark Reactions Occur in stroma of chloroplasts. 1._________ is added to a cycle of reactions to build larger molecules 2.A molecule of simple sugar is formed – _____________ CO 2 glucose


48 Video Summary of Photosynthesis

49 Photosynthesis Alternative Pathways C 4 plants The C 4 pathway allows plants to maintain photosynthesis while reducing water loss. Significant structural modification in the arrangement of cells within the leaves – separate CO 2 uptake from location of Calvin cycle

50 Photosynthesis Alternative Pathways CAM plants Crassulacean acid metabolism (CAM) is found in desert plants. Collect CO 2 at night and store it in organic compounds During the day, release CO 2 from organic compounds for the light-dependent cycle of photosynthesis

51 Bozeman Science: Photosynthesis g78utcLQrJ4

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 Living organisms obtain energy by breaking down organic molecules during cellular respiration. Section 3: Cellular Respiration K What I Know W What I Want to Find Out L What I Learned

55 Crash Course: Cellular Respiration 00jbG_cfGuQ

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 FE2jfTXAJHg

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 FADH 2. Finally, acetyl CoA and citric acid are generated and the cycle continues. Cellular Respiration

63 Steps of Kreb’s 1.Pyruvate broken down 2.Coenzyme A 3.Citric acid formed 4.Citric acid broken down 5.5-carbon molecule broken down 6.4-carbon molecule rearranged Up to 38 ATP molecules are made from the breakdown of 1 glucose molecule.


65 Khan Academy: Kreb Cycle juM2ROSLWfw

66 Video Kreb's cycle

67 Electron Transport In aerobic respiration, electron transport is the final step in the breakdown of glucose. NADH and FADH 2 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 1.Electrons removed – High energy electrons from NADH & FADH 2. 2.Hydrogen ions transported – High energy electrons travel through the proteins in the ETC. 3.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. 4.Water formed – Oxygen enters cellular respiration process & picks up electrons & hydrogen ions to form water.

70 Khan Academy: ETC mfgCcFXUZRk

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 – __________ ________ 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 PHOTOSYNTHESISCELLULAR RESPIRATION Organelle for processChloroplastMitochondrion ReactantsCO 2 & H 2 OSugars (C 6 H 12 O 6 ) & O 2 Electron Transport ChainProteins 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 6CO 2 + 6H 2 O C 6 H 12 O 6 + 6O 2 C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O ProductsSugars (C 6 H 12 O 6 ) & O 2 CO 2 & H 2 O Photosynthesis & Cellular Respiration

76 Photosynthesis and Cellular Respiration Cellular Respiration

77 Bozeman Science: Cellular Respiration Gh2P5CmCC0M

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

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