8/25/ Opening Questions: What is ENERGY? Chapter 4 Energy and Life: How do you make it through your day? How does a plant eat?

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1 Chapter 4 Energy and Life: 4.1 What is energy? 4.2 Energy flow 4.3 Sunlight is used to produce sugars 4.4 Photosynthesis has 2 linked stages 4.5 Light reactions: a closer look 4.6 Calvin cycle: a closer look 4.7 Cellular respiration overview 4.8 Cellular respiration: a closer look 4.9 Fermentation 4.10 Cellular respiration as a hub of metabolism 4.1 Opening Questions: What is ENERGY? How do you make it through your day? How does a plant eat? What powers a car? 4.1 Living things use energy to power life. All living things need energy to survive. But how do we define energy? Energy is defined as the capacity to do work. 4.1 Energy is converted from one form to another. Does the slider at the top of the slide contain energy? Potential energy is the energy an object has due to its location or structure. 4.1 Energy is converted from one form to another. What happens when the slider goes down the slide? 4.1 Potential energy is stored in the bonds that hold atoms together into molecules. In cells, ATP is a common energy currency molecule. Breaking a bond in ATP releases energy that can be used to drive other processes. Kinetic energy is the energy of motion. 1

2 4.1 Conservation of energy Energy can be converted but cannot be created or destroyed. Solar energy warms the lizard Heat energy dissipates 4.1 Heat is a by-product of energy conversion. After doing 100 jumping jacks, would you feel warm or cold? Chemical energy in lizard s food is stored and later converted to kinetic energy At each conversion some energy is lost to living things in the form of heat. 4.1 Living things must work to counter entropy. With each energy conversion heat is released, so the disorder in a system increases. Entropy is the amount of disorder in a system. Why don t living systems, like ecosystems or organisms, fall into complete disorder? 4.2 Opening Questions: What is the source of ENERGY for nearly all life? How do plants and animals get energy? What do plants and animals have in common in terms of energy acquisition? How do plants and animals differ? 4.2 Opening Questions: A thought experiment What would happen if the sun went out? How long could humans survive? Explain your ideas in a story. 4.2 Energy FLOWS through ecosystems. Solar energy is inputted daily. Energy therefore flows through living systems. Life on Earth is powered by the sun. 2

3 4.2 Producers and consumers: 4.2 Producers capture solar energy and convert it to chemical energy (sugars). Solar Energy converted to Chemical Energy Energy is stored in the bonds of sugar molecule. This is the process of PHOTOSYNTHESIS. Producers can absorb the sun s energy and convert it to chemical energy. They can make their own food! CO 2 + H 2 O SUGAR + O 2 Overall inputs and output of photosynthesis 4.2 Sugar production is the goal of photosynthesis. Photosynthesis takes place inside the cells of plants and algae in organelles called chloroplasts. Plants and algae produce oxygen gas (O 2 ) as a by-product. Interesting Fact: The Earth s atmosphere was low in O 2 prior to the evolution of photosynthesis. 4.2 Producers and consumers: Consumers obtain energy by eating producers. 4.2 Both producers and consumers must use cellular respiration. Photosynthesis converts solar energy into chemical energy. However, both producers and consumers are only able to release chemical energy through the process of cellular respiration. 4.2 Cellular respiration allows plants and animals to power life. The potential energy in the chemical bonds of sugar is converted to chemical energy. The kinetic energy can now be used for work. What kind of work might a plant or animal need to do? 3

4 4.3 Opening Question: Why is the grass green? Why do most of the plants we see everyday look green to us? 4.3 Where does photosynthesis take place? Most photosynthesis reactions occur inside plant cell organelles called chloroplasts. Photosynthesis is the process that provides food to nearly all life on Earth! 4.3 Photosynthesis: a visual overview 4.3 The chloroplast: a closer look Photosynthesis Inputs: H 2 O from ground and CO 2 from the air Photosynthesis Product: C 6 H 12 O 6 Inside the chloroplast there is an extensive framework of membranes. These facilitate the reactions of photosynthesis. By-product: O So why are plants green? Chlorophyll is the primary pigment (light-absorbing molecule) in chloroplasts. 4.3 Plants look green because chlorophyll reflects green light. The leaves of many deciduous trees change color in the fall. Can you think of an explanation? Light in the blue/violet and orange/red ranges is absorbed. Light in the green/yellow range is reflected. 4

5 4.4 Opening Question: Where does the mass of a plant come from? Tiny acorns grow into huge oak trees. Where does all the mass of the adult tree come from? 4.4 Photosynthesis: overall reaction The chemical inputs/output for photosynthesis are: 6CO 2 + 6H 2 O C 6 H 12 O 6 + 6O Photosynthesis occurs in two linked stages. 1. The light reactions capture sunlight and store it in high-energy molecules. 2. The Calvin cycle uses those highenergy molecules to produce sugar. Photosynthesis captures the energy in sunlight and stores it in the form of sugar molecules. 4.4 Stage 1: The LIGHT REACTIONS: capturing energy Energy from sunlight is absorbed by chlorophyll. H 2 O is split, producing O 2. High-energy molecules of ATP and NADPH are produced. Takes place in the thylakoid 4.4 Light reactions and Calvin cycle are linked by energy and electron shuttles. LIGHT REACTIONS NADPH ATP NADP+ ADP CALVIN CYCLE NADPH is a molecule that shuttles electrons. ATP is a molecule that shuttles energy. 4.4 Stage 2: The Calvin cycle: making sugar High-energy products from light reactions and CO 2 are used to make sugar (C 6 H 12 O 6 ). Where does the plant get CO 2? Calvin cycle takes place in the STROMA. 5

6 4.4 Review Question: Where does the mass of a plant come from? 4.5 Opening Question: Where does the O 2 produced in photosynthesis come from? Take a deep breath and thank a plant. Revise your answer using the chemical equation for photosynthesis. 4.5 Photosynthesis proceeds in two stages: overview 1. Light reactions Convert light energy to chemical energy 2. Calvin cycle Uses high-energy molecules (ATP, NADH) to produce sugars Inside a leaf both stages of photosynthesis are occurring. 4.5 A closer look at the light reactions: capturing sunlight as chemical energy The light reactions occur in the thykaloid membranes of the chloroplast. Pigment molecules capture the energy from sunlight. #1 pigment molecule is chlorophyll. 4.5 A closer look at the light reactions: major players and products Light System Players: Sunlight Water Splitting of H 2 O supplies electrons Chlorophyll ATP and ADP molecules NAPDH and NAPD molecules Light System Products: Energy Held in ATP Electrons Shuttled in NADH O 2 as a by-product ATP and NAPDH move to the Calvin cycle. 4.5 A closer look at the light reactions: 6

7 4.5 What happens to the water molecule? 4.6 Opening Questions: Plants at work Water (H 2 O) is used during the light reaction as a source of electrons. What remains of the water molecule (oxygen) is released and exits the leaf. How are a carrot and a piece of wood alike? How are they different? How did a plant make a carrot or a piece of wood? 4.6 A closer look at the Calvin cycle: making sugars Calvin cycle uses high-energy molecules from the light reactions to construct sugars. The plant can use sugars in a variety of ways. 4.6 Inputs to the Calvin cycle: Reminder: Photosynthesis is made up of two parts: light reaction and Calvin cycle. 4.6 Outputs from the Calvin cycle: 4.6 Plants are built of sugars! A 3-carbon sugar (G3P) is the output from the Calvin cycle. Plants use G3P to generate glucose. Glucose can be used for energy right away, or it can be stored. Plants store glucose in two ways. Both ways represent many glucose molecules stitched together. Starch Cellulose 7

8 4.7 Opening Questions: Part Opening Questions: Hungry? Everybody stand up. Shake your hands above your head! Dance party! What does burning Calories really mean? Why do we get hungry? Why do we need to breathe? Congratulations: You just burned about 6 Calories. 4.7 In CELLULAR RESPIRATION, oxygen is used to harvest the energy stored in sugar. Cellular respiration releases the chemical energy stored in sugars. ALL organisms both producers and consumers use cellular respiration! 4.7 Aerobic respiration: Aerobic respiration requires oxygen (O 2 ). It takes place inside the mitochondria. Aerobic respiration happens in both producers and consumers! 4.7 The ins and outs of aerobic respiration 4.7 The ins and outs of aerobic respiration 1. O 2 travels from lungs to the mitochondria. 2. Food travels from digestive system to the mitochondria. 3. CO 2 leaves the cell and is expelled from the lungs. 8

9 4.7 Three body systems play a role in cellular respiration. 4.7 Energy stored in ATP Cellular respiration produces an energycarrying molecule called ATP. 4.7 Kilocalories (kcal) 4.7 Kilocalories (kcal) A Calorie is the amount of chemical energy stored in food. A nutrition label is really showing you kilocalories (kcal), or thousands of Calories. A Calorie also can describe the amount of energy burned. Weight gain/loss is result of Calories in versus out. How long would you have to dance to burn off a candy bar? An orange? 4.8 Opening Questions: Toxic Spy Tales In old spy movies, a captured undercover agent, rather than risk spilling secrets, would swallow a hidden pill, which resulted in instant death. Very dramatic! Could such a pill really exist? How could a poison work so fast? 4.8 Cellular respiration is how life gets energy to power work. Cellular respiration uses O 2 to burn sugar (glucose). Energy is then used to generate ATP. By-products are CO 2 and H 2 O. Both plants and animals depend on cellular respiration 24 hours a day, every second, in every cell. 9

10 4.8 Cellular respiration overview: 4.8 Cellular respiration: overall reaction The chemical inputs/output for cellular respiration are: C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O How does the overall equation for cellular respiration compare with photosynthesis? 4.8 Study tip: The chemical inputs for cellular respiration and photosynthesis are reciprocal! Photosynthesis Light Energy Chemical Energy 4.8 Cellular respiration has three stages. 1. Glycolysis 2. Citric acid cycle 3. Electron transport chain 6CO 2 + 6H 2 O C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O C 6 H 12 O 6 + 6O 2 Cellular respiration Chemical Energy ATP Energy 4.8 Glycolysis: 4.8 Citric acid cycle: Takes place in cytoplasm Splits glucose into 2 pyruvic acids Small amount of ATP produced Takes place in the mitochondrial fluid Uses O 2 Pyruvic acid broken to CO 2 High-energy electrons produced Small amount of ATP produced 10

11 4.8 Electron transport chain: Takes place in the inner membranes of mitochondria High-energy electrons move through chain Electrons combine with O 2 to form H 2 O Lots of ATP produced! 4.8 Test your understanding: The toxic tale of the spy movie The spy pills were made of potassium cyanide, which interrupts the electron transport chain. What would happen to your ATP production? How long could your cells survive? 4.9 Opening Questions: What makes your beer carbonated? Where do the bubbles come from in beer? What about the alcohol? Explain. 4.9 In fermentation, energy is harvested from sugar without oxygen. Aerobic respiration Anaerobic respiration 4.9 Fermentation is anaerobic. 4.9 Lactic acid fermentation in muscles Fermentation harvests the energy from glucose without O 2. Only a small bit of ATP is produced. O 2 When cells can t get O 2, lactic acid fermentation is an emergency mode. Fermentation produces much less ATP than aerobic respiration! Why can t muscle cells run for long on fermentation? 11

12 4.9 Lactic acid fermentation by bacteria 4.9 Alcohol fermentation by yeast Unlike muscle cells, some bacteria can survive on fermentation. Humans have domesticated many strains. Yeast will ferment sugars in anaerobic environments. This produces CO 2 and alcohol (ethanol). Why does yogurt have a tangy taste? CO 2 is a gas! So what happens when CO 2 is in a liquid? 4.10 Opening Question: Sugar rush If cellular respiration burns sugars, can we get energy from other foods? 4.10 Cellular respiration is a central hub of many of life s metabolic processes. Many types of molecules can feed into cellular respiration. In addition to sugar, we can process Fats Carbohydrates Proteins This means we can generate ATP from many different food inputs All food provides energy Energy use by living things. Your metabolism is the sum total of all the chemical reactions that occur in your body. ATP produced by cellular respiration powers nearly all of life s processes. 12