1 Chapter 8 Energy & Life

Cell Energy Energy is essential to life. All living organisms must: be able to produce energy store energy for future use, and use energy.

The need for energy Several cell processes require energy –Active transport –Cell division –Movement of flagella or cilia –Production and storage of proteins –What else?

…more uses of cell energy Making new molecules Enzymes which carry out chemical reactions To build membranes and cell organelles Maintain homeostasis Kidneys uses energy to move molecules and ions in order to eliminate waste substances while keeping needed substances in the bloodstream

The need for energy (cont.) When you finish strenuous activity, your body wants a quick source of energy, so you may eat a candy bar. There is a molecule in your cells that is a quick source of energy for any organelle in the cell that needs it. This is stored in the chemical bonds of the molecule and can be used quickly and easily by the cell.

ATP and ADP ATP is the molecule that stores energy for easy use within the cell. (Adenosine triphosphate) –A–ATP is formed when a phosphate group is added to ADP. When ATP is broken down, ADP and phosphate are formed and energy is released. (Adenosine Diphosphate) –A–ATP is the main link between energy – releasing and energy –using reactions

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8 Cells Using Biochemical Energy Cells Use ATP For: Active transport Movement Photosynthesis Protein Synthesis Cellular respiration All other cellular reactions

9 More on ATP Cells Have Enough ATP To Last For A Few SecondsCells Have Enough ATP To Last For A Few Seconds ATP must constantly be madeATP must constantly be made ATP Transfers Energy Very WellATP Transfers Energy Very Well ATP Is NOT Good At Energy StorageATP Is NOT Good At Energy Storage

10 Autotrophs Plants and some other types of organisms that contain chlorophyll are able to use light energy from the sun to produce food.

11 Autotrophs Autotrophs include organisms that make their own foodAutotrophs include organisms that make their own food Autotrophs can use the sun’s energy directlyAutotrophs can use the sun’s energy directly Euglena

12 Heterotrophs Heterotrophs are organisms that can NOT make their own foodHeterotrophs are organisms that can NOT make their own food Heterotrophs can NOT directly use the sun’s energyHeterotrophs can NOT directly use the sun’s energy

13 Glucose Glucose is a monosaccharideGlucose is a monosaccharide C 6 H 12 O 6C 6 H 12 O 6 One Molecule of glucose Stores 90 Times More Chemical Energy Than One Molecule of ATPOne Molecule of glucose Stores 90 Times More Chemical Energy Than One Molecule of ATP

14 History of Photosynthesis & Plant Pigments

15 Photosynthesis Involves the Use Of light Energy to convert Water (H 2 0) and Carbon Dioxide (CO 2 ) into Oxygen (O 2 ) and High Energy Carbohydrates (sugars, e.g. Glucose) & StarchesInvolves the Use Of light Energy to convert Water (H 2 0) and Carbon Dioxide (CO 2 ) into Oxygen (O 2 ) and High Energy Carbohydrates (sugars, e.g. Glucose) & Starches

16 Investigating Photosynthesis Many Scientists Have Contributed To Understanding PhotosynthesisMany Scientists Have Contributed To Understanding Photosynthesis Early Research Focused On The Overall ProcessEarly Research Focused On The Overall Process Later Researchers Investigated The Detailed Chemical PathwaysLater Researchers Investigated The Detailed Chemical Pathways

17 Early Questions on Plants Several Centuries Ago, The Question Was: Does the increase in mass of a plant come from the air? The soil? The Water?

18 Van Helmont’s Experiment 1643 Planted a seed into A pre-measured amount of soil and watered for 5 yearsPlanted a seed into A pre-measured amount of soil and watered for 5 years Weighed Plant & Soil. Plant Was 75 kg, Soil The Same.Weighed Plant & Soil. Plant Was 75 kg, Soil The Same. Concluded Mass Came From WaterConcluded Mass Came From Water

19 Priestley’s Experiment 1771 Burned Candle In Bell Jar Until It Went Out. Placed Sprig Of Mint In Bell Jar For A Few Days. Candle Could Be Relit And Burn. Concluded Plants Released Substance (O 2 ) Necessary For burning.

20 Ingenhousz’s Experiment 1779 Repeated Priestly experiment with & without sunlight

21 Results of Ingenhousz’s Experiment Showed That Priestley’s Results Only Occurred In The Presence Of Sunlight.Showed That Priestley’s Results Only Occurred In The Presence Of Sunlight. Light Was Necessary For Plants To Produce The “Burning Gas” or oxygenLight Was Necessary For Plants To Produce The “Burning Gas” or oxygen

22 Julius Robert Mayer 1845 Proposed That Plants can Convert Light Energy Into Chemical Energy

23 Samuel Ruben & Martin Kamen 1941 Used Isotopes To Determine That The Oxygen Liberated In Photosynthesis Comes From Water KAMEN RUBIN

24 Melvin Calvin 1948 First to trace the path that carbon (CO 2 ) takes in forming GlucoseFirst to trace the path that carbon (CO 2 ) takes in forming Glucose Does NOT require sunlightDoes NOT require sunlight Called the Calvin Cycle or Light Independent ReactionCalled the Calvin Cycle or Light Independent Reaction Also known as the Dark ReactionAlso known as the Dark Reaction

25 Rudolph Marcus 1992 Studied the Light Independent ReactionsStudied the Light Independent Reactions First to describe the Electron transport ChainFirst to describe the Electron transport Chain

26 The Photosynthesis Equation

27 Pigments In addition to water, carbon dioxide, and light energy, photosynthesis requires Pigments Chlorophyll is the primary light-absorbing pigment in autotrophs Chlorophyll is found inside chloroplasts

28 It Begins with Sunlight!

29 Photoautotrophs Absorb Light Energy

30 Question: Where does photosynthesis take place?

31 Plants Autotrophs – produce their own food (glucose)Autotrophs – produce their own food (glucose) Process called photosynthesisProcess called photosynthesis Mainly occurs in the leaves:Mainly occurs in the leaves: a.stoma - pores b.mesophyll cells Stoma Mesophyll Cell Chloroplast

32 Stomata (stoma) Pores in a plant’s cuticle through which water and gases are exchanged between the plant and the atmosphere. Guard Cell Carbon Dioxide (CO 2 ) Oxygen (O 2 ) Found on the underside of leaves

33 Mesophyll Cell of Leaf Cell Wall Nucleus Chloroplast Central Vacuole Photosynthesis occurs in these cells!

34 Inside A Chloroplast

35 Chloroplast Organellephotosynthesis Organelle where photosynthesis takes place. Granum Thylakoid Stroma Outer Membrane Inner Membrane Thylakoid stacks are connected together

36 Thylakoid Thylakoid Membrane Thylakoid Space Granum Grana make up the inner membrane

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38 Function of the Stroma Light Independent reactions occur hereLight Independent reactions occur here ATP used to make carbohydrates like glucoseATP used to make carbohydrates like glucose Location of the Calvin CycleLocation of the Calvin Cycle

39 Photosynthesis Overview

40 Harvesting Light energy Within the inner membrane of the chloroplast, is the stroma which contains the thylakoid membrane. This membrane produces flat, disc-like sacs called thylakoids that are arranged in stacks and contain molecules that absorb light energy for photosynthesis

41 Light Reaction Summary Reactants: H 2 OH 2 O Light EnergyLight Energy Energy Products: ATPATP NADPHNADPHProducts: O 2O 2

42 Light Independent Reaction summary ATP and NADPH from light reactions used as energyATP and NADPH from light reactions used as energy Atmospheric C0 2 is used to make sugars like glucose and fructoseAtmospheric C0 2 is used to make sugars like glucose and fructose Six-carbon Sugars made during the Calvin CycleSix-carbon Sugars made during the Calvin Cycle Occurs in the stromaOccurs in the stroma

43 The Calvin Cycle Carbon Fixation (light independent reaction) Carbon Fixation (light independent reaction) C 3 plants (80% of plants on earth) C 3 plants (80% of plants on earth) Occurs in the stroma Occurs in the stroma Uses ATP and NADPH from light reaction as energy Uses ATP and NADPH from light reaction as energy Uses CO 2 Uses CO 2 To produce glucose: it takes 2 turns and uses 18 ATP and 12 NADPH. To produce glucose: it takes 2 turns and uses 18 ATP and 12 NADPH.

44 Factors Affecting the Rate of Photosynthesis Amount of available waterAmount of available water TemperatureTemperature Amount of available light energyAmount of available light energy

Formula for Photosynthesis Light–dependent reactions convert light energy into chemical energy (molecules of ATP) Light–independent reactions are fueled by the ATP produced to produce glucose.

46 Question: During the fall, what causes the leaves to change colors?

47 Fall Colors In addition to the chlorophyll pigments, there are other pigments presentIn addition to the chlorophyll pigments, there are other pigments present During the fall, the green chlorophyll pigments are greatly reduced revealing the other pigmentsDuring the fall, the green chlorophyll pigments are greatly reduced revealing the other pigments Carotenoids are pigments that are either red, orange, or yellowCarotenoids are pigments that are either red, orange, or yellow