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Biology 1 Mr. Greene Unit 4 List as many different forms of energy as you can. Give an example of each type of energy. What type of energy is used in cells, and what is the ultimate source of this energy? How is an organism’s metabolism related to the carbon cycle? How is energy released in a cell? the ability to do work Kinetic energy energy of motion ▪ stick swinging Potential energy stored energy ▪ stick caught in midswing autotrophs organisms which make their own food heterotrophs organisms which rely on outside sources for food eat autotrophic organisms eat organisms that eat autotrophs Most energy on Earth comes from the sun. plants, some bacteria, algae get energy from sunlight they undergo a process called photosynthesis 1% of light energy that reaches Earth is converted to chemical energy Organisms require a constant source of energy. Energy is needed for organisms to maintain their homeostasis. Homeostasis is the process of maintaining internal order and balance even when the environment changes. Organisms use and store energy in the chemical bonds of organic compounds. Almost all of the energy in organic compounds comes from the sun. Photosynthesis is the process by which plants, algae, and some bacteria use sunlight, carbon dioxide, and water to produce carbohydrates and oxygen. Organisms that are able to perform photosynthesis, such as plants, are autotrophs. Autotrophs make organic compounds that serve as food for them and for almost all of the other organisms on Earth, Organisms that cannot make their own food must absorb food molecules made by autotrophs, eat autotrophs, or eat organisms that consume autotrophs. Food molecules that are made or consumed by an organism are the fuel for its cells. Cells use these molecules to release the energy stored in the molecules’ bonds. The energy is used to carry out life processes. Click above to play the video. Metabolism involves either using energy to build organic molecules or breaking down organic molecules in which energy is stored. Organic molecules contain carbon. Therefore, an organism’s metabolism is part of Earth’s carbon cycle. Energy from the sun is converted to chemical energy in chloroplasts. Organisms extract energy in glucose molecules. Through the process of cellular respiration, cells make the carbon in glucose into stable carbon dioxide molecules and produce energy. Energy is also released and used to make ATP (adenosine triphosphate), an organic molecule that is the main energy source for cell processes. ATP When cells break down food molecules, some of the molecules are released as heat. Much of the remaining energy makes ATP. ATP is a portable form of energy “currency” inside cells. ATP is a nucleotide made up of a chain of three phosphate groups. When the bond of the third phosphate group is broken, energy is released, producing ADP. ATP Adenine Ribose 3 Phosphate groups - adenosine triphosphate - the energy currency - ATP must be able to absorb NRG and release it where it is needed Comparison of ADP and ATP to a Battery ADP ATP Energy Adenosine diphosphate (ADP) + Phosphate Energy Partially charged battery Adenosine triphosphate (ATP) Fully charged battery Comparison of ADP and ATP to a Battery ADP ATP Energy Adenosine diphosphate (ADP) + Phosphate Partially charged battery Energy Adenosine triphosphate (ATP) Fully charged battery Click above to play the video. In many cells, ATP synthase recycles ADP by bonding a third phosphate group to the molecule to form ATP. ATP synthase acts as both an enzyme and a carrier protein for hydrogen ions. The flow of H+ ions through ATP synthase powers the production of ATP. In chloroplasts and mitochondria, a series of molecules, called an electron transport chain, pump H+ ions across the membrane to create a concentration gradient. The electron transport chain uses energy from released from electron carriers, such as NADH and NADPH, to pump hydrogen ions. Organisms use and store energy in the chemical bonds of organic molecules. Metabolism involves either using energy to build organic molecules or breaking down organic molecules in which energy is stored. Organic molecules contain carbon. Therefore, an organism’s metabolism is part of Earth’s carbon cycle. In cells, chemical energy is gradually released in a series of chemical reactions that are assisted by enzymes. Write down the primary role that sunlight plays in living systems, and then define photosynthesis. What is the role of pigments in photosynthesis? What are the roles of the electron transport chains? How do plants make sugars and store extra unused energy? What are the three environmental factors that affect photosynthesis? Photosynthesis is the process that provides energy for almost all life. Chloroplasts are the organelles that convert light energy into chemical energy. Within the inner membrane of the chloroplast, is the stroma which contains the thylakoid membrane. This membrane produces flat, disclike sacs called thylakoids that are arranged in stacks and contain molecules that absorb light energy for photosynthesis. Photosynthesis: Reactants and Products Light Energy Chloroplast CO2 + H2O Sugars + O2 Photosynthesis: An Overview Light CO2 Chloroplast Chloroplast NADP+ ADP + P LightDependent Reactions Calvin Cycle ATP NADPH O2 Sugars Light is a form of electromagnetic radiation, energy that can travel through empty space in the form of waves. Sunlight contains all of the wavelengths of visible light which we see as different colors. A pigment is a substance that absorbs certain wavelengths (colors) of light and reflects all of the others. Chlorophyll is a green pigment in chloroplasts that absorbs light energy to start photosynthesis. It absorbs mostly blue and red light and reflects green and yellow light, which makes plants appear green. Plants also have pigments called carotenoids which help plants absorb additional light energy. When light hits a thylakoid, energy is absorbed by many pigment molecules and eventually transferred to electron carriers. Producing ATP Step 1: Electrons excited by light leave the chlorophyll molecules. An enzyme splits water molecules to replace these electrons. Oxygen gas is formed and released into the atmosphere. Producing ATP Step 2: Excited electrons transfer some of their energy to pump H+ ions into the thylakoid. This process creates a concentration gradient across the thylakoid membrane. Producing ATP Step 3: The energy from diffusion of H+ ions through the channel portion of ATP synthase is used to catalyze a reaction in which a phosphate group is added to a molecule of ADP, producing ATP. Producing NADPH Step 4: Light excites electrons in another chlorophyll molecule. The electrons are passed on to the second chain and replaced by the deenergized electrons from the first chain. Producing NADPH Step 5: Excited electrons combine with H+ ions and NADP+ to form NADPH. NADPH is an electron carrier that provides high-energy electrons needed to store energy in organic molecules. Click to animate the image. The first two stages of photosynthesis depend directly on light because light energy is used to make ATP and NADPH. In the final stage of photosynthesis, ATP and NADPH are used to produce energy-storing sugar molecules from the carbon in carbon dioxide. The use of carbon dioxide to make organic compounds is called carbon dioxide fixation, or carbon fixation. The reactions that fix carbon dioxide are lightindependent reactions, sometimes called dark reactions. The most common method of carbon fixation is the Calvin cycle. Atmospheric carbon dioxide is combined with other carbon compounds to produce organic compounds. ATP and NADPH supply some of the energy required in these reactions. Calvin Cycle CO2 Enters the Cycle PGA Energy Input RuBP 5-Carbon Molecules Regenerated PGAL 6-Carbon Sugar Produced Sugars and other compounds ChloropIast Click above to play the video. Light intensity, carbon dioxide concentration, and temperature are three environmental factors that affect photosynthesis. Although different plants are adapted to different levels of light, the photosynthesis rate increases with increases in light intensity until all of the pigments in a chloroplast are being used. Photosynthesis is most efficient in a certain range of temperatures. In plants, light energy is harvested by pigments located in the thylakoid membrane of chloroplasts. During photosynthesis, one electron transport chain provides energy used to make ATP, while the other provides energy to make NADPH. In the final stage of photosynthesis, chemical energy is stored by being used to produce sugar molecules from the carbon in the gas carbon dioxide. Light intensity, carbon dioxide concentration, and temperature are three environmental factors that affect photosynthesis. Answer the following questions: How are the products of photosynthesis and respiration related? What kinds of organisms undergo cellular respiration? How does glycolysis produce ATP? How is ATP produced in aerobic respiration? Why is fermentation important? Glucose Glycolysis Krebs cycle Fermentation (without oxygen) Electron transport Alcohol or lactic acid The cells of most organisms transfer energy found in organic compounds, such as those in foods, to ATP. The primary fuel for cellular respiration is glucose. Fats can be broken down to make ATP. Proteins and nucleic acids can also be used to make ATP, but they are usually used for building important cell parts. In glycolysis, enzymes break down one six-carbon molecule of glucose into two three-carbon pyruvate molecules. The breaking of a sugar molecule by glycolysis results in a net gain of two ATP molecules. This process of glycolysis is anaerobic, or takes place without oxygen. Click above to play the video. Glycolysis is the only source of energy for some prokaryotes. Other organisms use oxygen to release even more energy from a glucose molecule. Metabolic processes that require oxygen are aerobic. In aerobic respiration, the pyruvate product of glycolysis undergoes another series of reactions to produce more ATP molecules. Organisms such as humans can use oxygen to produce ATP efficiently through aerobic respiration. The first stage of aerobic respiration is the Krebs cycle, a series of reactions that produce electron carriers. The electron carriers enter an electron transport chain, which powers ATP synthase. Up to 34 ATP molecules can be produced from one glucose molecule in aerobic respiration. Krebs Cycle Pyruvate (from glycolysis) is broken down and combined with other carbon compounds. Each time the carbon-carbon bonds are rearranged during the Krebs cycle, energy is released. The total yield of energy-storing products from one time through the Krebs cycle is one ATP, three NADH, and one FADH2. Citric Acid Production Mitochondrion Click above to play the video. Electron Transport Chain The second stage of aerobic respiration takes place in the inner membranes of mitochondria, where ATP synthase enzymes are located. Electron carriers, produced during the Krebs cycle, transfer energy through the electron transport chain. Energy from the electrons is used to actively transport hydrogen ions out of the inner mitochondrial compartment. Electron Transport Intermembrane Space Hydrogen Ion Movement Channel Mitochondrion ATP synthase Inner Membrane Matrix ATP Production Click above to play the video. Electron Transport Chain Hydrogen ions diffuse through ATP synthase, providing energy to produce several ATP molecules from ADP. At the end of the electron transport chain, the electrons combine with an oxygen atom and two hydrogen ions to form two water molecules. If oxygen is not present, the electron transport chain stops. The electron carriers are not recycled, so the Krebs cycle also stops. To make ATP during glycolysis, NAD+ is converted to NADH. Organisms must recycle NAD+ to continue making ATP through glycolysis. The process in which carbohydrates are broken down in the absence of oxygen is called fermentation. Fermentation enables glycolysis to continue supplying a cell with ATP in anaerobic conditions. In lactic acid fermentation, pyruvate is converted to lactic acid. During vigorous exercise, lactic acid fermentation also occurs in the muscles of animals, including humans. During alcoholic fermentation, one enzyme removes carbon dioxide from pyruvate. A second enzyme converts the remaining compound to ethanol, recycling NAD+ in the process. Efficiency of Cellular Respiration In the first stage of cellular respiration, glucose is broken down to pyruvate during glycolysis, an anaerobic process. Glycolysis results in a net gain of two ATP molecules for each glucose molecule that is broken down. In the second stage, pyruvate either passes through the Krebs cycle or undergoes fermentation. Fermentation recycles NAD+ but does not produce ATP. Efficiency of Cellular Respiration Cells release energy most efficiently when oxygen is present because they make most of their ATP during aerobic respiration. For each glucose molecule that is broken down, as many as two ATP molecules are made during the Krebs cycle. The Krebs cycle feeds NADH and FADH2 to the electron transport chain, which can produce up to 34 ATP molecules. P deposits energy removes CO2 releases O2 plants, algae, some bacteria CR withdraws energy puts CO2 back uses O2 all eukaryotes, some prokaryotes The breaking of a sugar molecule by glycolysis results in a net gain of two ATP molecules. The total yield of energy-storing products from one time through the Krebs cycle is one ATP, three NADH, and one FADH2. Electron carriers transfer energy through the electron transport chain, which ultimately powers ATP synthase. Fermentation enables glycolysis to continue supplying a cell with ATP in anaerobic conditions.
