Chapter 5. Chapter 5. Objectives Analyze the flow of energy through living systems. (5.1) New Vocabulary. Vocabulary Review. Chapter 5.

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1 Photosynthesis and Cellular Respiration Section 1 and Section 2 Photosynthesis and Cellular Respiration Why It s Important Every cell in your body needs energy to function. This energy is acquired through photosynthesis and cellular respiration Objectives Analyze the flow of energy through living systems. (5.1) Compare the metabolism of autotrophs with that of heterotrophs. (5.1) Describe the role of ATP in metabolism. (5.1) Describe the experiments that led to an understanding of photosynthesis (5.2) Summarize how energy is captured from sunlight in the first stage of photosynthesis. (5.2) New Vocabulary Section 5.1 Photosynthesis Autotroph Heterotroph Cellular respiration Section 5.2 Pigment Chlorophyll Carotenoid Thylakoid Granum / grana stroma Vocabulary Review What is metabolism? All of an organism s chemical reactions Energy in Living Systems Directly or indirectly, almost all of the energy in living systems needed for metabolism comes from the sun Metabolism involves either building molecules or breaking down molecules in which energy is stored. Photosynthesis is the process by which light energy is converted to chemical energy This chemical energy is stored in the organic compound, glucose which is a plant s food Often, plants convert glucose to, starch which can be stored in stems and roots for later use Organisms that carry out photosynthesis are called autotrophs

2 Equation for Photosynthesis Light Energy 6CO 2 + 6H > C 6 H O 2 Carbon dioxide Water Glucose Oxygen What are the reactants? Carbon dioxide and water What are the products? Glucose and oxygen Which substance acts a catalyst? Light energy How did we learn about photosynthesis? By studying plant growth The work of three major scientists has led to our understanding of photosynthesis Jan van Helmont Joseph Priestley Jan Ingenhousz Jan van Helmont 17 th century Dutch physician devised an experiment to find out where the mass of a growing tree comes from 1. Carefully found the mass of a pot of dry soil and a small seedling 2. Planted the seedling in the pot of soil 3. Took care of it and watered it for five years. Van Helmont s Result At the end of five years, the seedling had grown into a small tree The tree gained a mass of about 75 kg, while the mass of the soil was almost unchanged Conclusion? The mass of a tree comes from water because it was the only thing he added to the soil Joseph Priestley English scientist conducted an experiment nearly 100 years after Van Helmont 1. Placed a glass jar over a burning candle 2. Watched as the flame gradually died out and concluded that something in the air was needed for the candle to continue burning Priestley ran the experiment again with a small plant in the container After a few days, Priestley attempted to relight the candle with a burning. glass It! relit Conclusion? Plants produce, oxygen which allowed the candle to burn

3 Priestley did similar experiments with plants and he mice discovered that oxygen is also necessary to sustain animal life Do not try this at home! While unintentionally cruel, this discovery was very important! Previously, scientists believed that air was an element and did not know that it contained separate gases Jan Ingenhousz Dutch scientist conducted Priestley s experiment in the presence and absence of light Observed similar results only in the presence of light Conclusion? light is necessary for plants to produce oxygen Ingenhousz (light house) The work of Van Helmont, Priestley, and Ingenhousz constructed part of the chemical equation for photosynthesis Light Energy + H > C 6 H O 2 What reactant(s) was/were contributing to the carbon and oxygen and in glucose? In the 1950s, scientists placed radioactive, markers or tags on the oxygen in CO 2 and H 2 0 to track their reactions during photosynthesis Result The oxygen in CO 2 was incorporated into glucose and the oxygen in H 2 0 was released as a gas Light Energy CO 2 + H > C 6 H 12 O 6 + O 2 The chemical energy in organic compounds can be transferred to other organic compounds or to organisms that consume food. Organisms that must get energy by consuming other organisms are called heterotrophs Examples Rabbits consume grass A fox consumes rabbits Both plants and animals need a way to break down their food so that it can be used to carry out cellular activities Organisms do so in a process called cellular respiration This process converts the chemical energy stored in glucose or starch into a usable form of energy called ATP

4 Cellular Respiration Equation enzymes C 6 H 12 O 6 + 6O > 6C H 2 O + energy glucose oxygen carbon dioxide water ATP What are the reactants? glucose and oxygen What are the products? Carbon dioxide, water, and ATP Which substance acts as a catalyst? enzymes Cellular Respiration Equation enzymes C 6 H 12 O 6 + 6O > 6C H 2 O + energy glucose oxygen carbon dioxide water ATP How are the equations for cellular respiration and oxygen related? photosynthesis The reactants and products are reversed Transfer of Energy to ATP O 2 When cells break down food molecules, some of the energy in the molecules is released as, heat while the remaining energy is stored in ATP. plant animal Like money, ATP is a portable form of energy currency inside cells It delivers energy wherever energy is needed in a cell CO 2 Breakdown of Starch ATP ATP, which stands for adenosine, triphosphate is actually a nucleotide with two extra energy-storing phosphate groups. What are the three basic parts of a nucleotide? Phosphate group Sugar Nitrogenous base

5 So ATP is made up of a. sugar Nitrogenous base 3 phosphate groups Where is energy stored in ATP? In the bonds between the phosphates Energy is released when the bonds that hold the phosphate groups together are broken The removal of a phosphate group from ATP produces ADP, which stands for adenosine diphosphate H 2 O + ATP ADP + P + energy ATP Releases Energy Photosynthesis occurs in three stages Stage 1 Energy is captured from sunlight. Stage 2 Light energy is converted to chemical energy, which is temporarily stored in ATP and the electron carrier molecule. NADPH Stage 3 The chemical energy stored in ATP and NADPH powers the formation of organic, compounds using. CO 2 chloroplast These stages occur in different parts of the Each green stack inside the chloroplast is called a granum The grana are made up of individual thylakoids which have their own membranes called thylakoid membranes granum Photosynthesis Stages 1 & 2 occur in the thylakoid, membrane while stage 3 occurs outside of the grana in the space called the stroma

6 Stage One: Capture of Light Energy Sunlight contains a mixture of all the wavelengths (colors) of visible light When sunlight passes through a, prism the prism separates the light into different colors. According to increasing frequency, the wavelengths are Red Orange Yellow Green Blue Indigo Violet Hint ROYGBIV Increasing frequency (energy) reflected Wavelengths that are seen are Think of mirror what is the image called that you see? reflection Wavelengths that are not seen are absorbed Leaves contain light-absorbing substances called pigments Chlorophyll a Chlorophyll b carotenoids What colors do chlorophyll b and a absorb? Violet, blue, orange and red So chlorophyll reflects Green and yellow What colors do carotenoids reflect that chlorophyll does not? orange and red.fall colors

7 These pigments are embedded in the thylakoid membrane which surround the grana When light strikes the membrane, energy is transferred to electrons in chlorophyll molecules This energy transfer causes the electrons to jump to a higher energy level. When electrons are at the lowest energy level they are at the ground state When they absorb energy, they become excited and move to higher energy levels Plants first capture the sun s energy when electrons in their chlorophyll molecules absorb its wavelengths Excited electrons eventually move back down to the ground state As they do, they release their absorbed energy Question 1 What molecule that contains chemical energy is produced in photosynthesis? A. O 2 B. CO 2 C. C 6 H 12 O 6 D. H 2 0 Question 2 What is the difference between autotrophs and heterotrophs? Autotrophs make their own food Heterotrophs must consume food Question 3 Which scientist determined that the process of photosynthesis requires light? A. Jan van Helmont B. Joseph Priestley C. Jan Ingenhousz

8 Question 4 An ATP molecule is a nucleotide with two more A. Nitrogenous bases B. Phosphate groups C. Sugars D. Glycerol molecules Question 5 Do chlorophyll molecules reflect or absorb green light? reflect Question 6 In order of increasing frequency, what do the first letter of each color in visible light spell? ROYGBIV