CH 8/9 NOTES Photosynthesis and Cellular Respiration 1 Chemical Energy Energy is the ability to do work. Your cells are busy using energy to build new molecules, contract muscles, and carry out active transport. Without the ability to obtain and use energy, life would cease to exist. 2 ATP/ADP One of the most important compounds that cells use to store and release energy is adenosine triphosphate (ATP). ATP consists of adenine, a 5-carbon sugar called ribose, and three phosphate groups. 3 Why is ATP useful to cells? ATP can easily release and store energy by breaking and re-forming the bonds between its phosphate groups. This characteristic of ATP makes it exceptionally useful as a basic energy source for all cells. 4 Storing Energy Adenosine diphosphate (ADP) has two phosphate groups instead of three. ADP contains some enrgy, but not as much as ATP. . 5 Storing Energy How is ADP like a rechargeable battery? it can store small amounts of it by adding phosphate groups to ADP, producing ATP. Energy is released by breaking the bonds between the 2 nd and 3 rd phosphate groups. 6 Using Biochemical Energy One way cells use the energy provided by ATP is to carry out active transport in order to run the protein pumps. 7 Using Biochemical Energy ATP powers movement, providing the energy for motor proteins that contract muscle and power the movement of cilia and flagella. 8 Using Biochemical Energy Energy from ATP powers the synthesis of proteins and responses to chemical signals at the cell surface. 9 Using Biochemical Energy ATP is not a good molecule for storing large amounts of energy over the long term. It is more efficient for cells to keep only a small supply of ATP on hand. Cells can regenerate ATP from ADP as needed by using the energy in foods like glucose. 10 Heterotrophs and Autotrophs Organisms that obtain food by consuming other living things are known as heterotrophs. Examples Some heterotrophs get their food by eating plants. Other heterotrophs, such as a cheetah, obtain food from plants indirectly by feeding on plant-eating animals. Still other heterotrophs, such as mushrooms, obtain food by decomposing other organisms. 11 Heterotrophs and Autotrophs Organisms that make their own food are called autotrophs. Where do they get their energy? Sunlight! (or chemicals in deep sea vents) 3 examples of autotrophs Plants, algae, and some bacteria are able to use light energy from the sun to produce food. (photosynthesis) 12 PHOTOSYNTHESIS Photosynthesis is changing the energy of sunlight into chemical energy stored in the bonds of carbohydrates. 13 Light Sunlight is a mixture of different energy wavelengths, many of which are visible to our eyes and make up the visible spectrum. List the colors we see in wavelength order: Violet, blue, green, yellow, orange, red Pigments Plants gather the suns energy with light- absorbing molecules called pigments. The plants principal pigment is chlorophyll. Leaves reflect green light, which is why plants look green. 15 Pigments The chlorophyll absorbs all colors of light except for green. Chlorophyll reflect green light, which is why plants look green. 16 Pigments As temperatures drop the chlorophyll molecules break down, and the red and orange pigments may be seen. 17 Review What is the difference between ATP and ADP? What are the three parts of ATP? What is the difference between an autotroph and a heterotroph? Explain how the pigment chlorophyll works. Why are plants green? Why do plants turn other shades of color as seasons progress? Chloroplasts Photosynthesis takes place (cross out on) in autotrophs inside organelles called chloroplasts. Chloroplasts contain saclike photosynthetic membranes called thylakoids, which are interconnected and arranged in stacks known as grana. 19 Chloroplasts Pigments are located in the thylakoid membranes. The fluid portion outside of the thylakoids is known as the stroma. 20 Energy Collection Because light is a form of energy, any compound that absorbs light absorbs energy. Chlorophyll absorbs visible light especially well. When chlorophyll absorbs light, a large fraction of the light energy is transferred to electrons. These high-energy electrons make photosynthesis work. 21 An Overview of Photosynthesis Photosynthesis uses the energy of sunlight to convert water and carbon dioxide into high-energy sugars and oxygen. In symbols: Chemical Equation: 6 CO H 2 O C 6 H 12 O O 2 In words: Carbon dioxide + Water Sugars + Oxygen 22 Factors Affecting Photosynthesis Temperature The reactions of photosynthesis are made possible by enymes that function best between 0 degrees C And 35 degrees C. Temperatures above or below this range may affect those enzymes, slowing down or stop entirely. Factors Affecting Photosynthesis Light High light intensity increases the rate of photosynthesis. After the light intensity reaches a certain level, however, the plant reaches its maximum rate of photosynthesis. Factors Affecting Photosynthesis And Water Because water is one of the raw materials in photosynthesis, a shortage of water can slow or even stop photsynthesis. Plants that lie in dry conditions often have waxy coatings on their leaves to reduce water loss. They may also have biochemical pathways that make photosynthesis more efficient under dry conditions. Light-Dependent Reactions Photosynthesis involves two sets of reactions: Light-dependent reaction Light-Independent reaction(also known as the Calvin Cycle) 26 Light-Dependent Reactions Depends on light and water. Takes place in the thylakoid membranes of the chloroplasts. They produce oxygen and convert ADP and NADP+ into the energy carriers ATP and NADPH. 27 Light Dependent Reactions Generating ATP and NADPH What is a photosystem? Photosystem II, energy from light is absorbed by chlorophyll and transferred to electrons, and then these high energy electrons are passed on to the electron transport chain Photosystem I-pigments use energy from light to reenergize the electrons. Light-Independent Reactions energy (ATP) from light reaction is required to power the light-independent reactions (The Calvin Cycle!) Plants absorb carbon dioxide from the atmosphere and produce glucose and other carbohydrates. The light independent reactions take place outside the thylakoids, in the stroma 29 Light Independent Reactions Producing Sugars The common name for the light-independent reactions is the Calvin Cycle. What is being made in the reaction? Glucose! The Calvin Cycle: How many new carbon molecules are produced for every 6 carbon dioxide molecules? A single 6 carbon sugar molecule. What are these molecules used for? To build more complex carbs that the plants need for growth and development. The End Results The two sets of photosynthetic reactions work together The light dependent reactions trap the energy of sunlight in chemical form. The light independent reactions (The Calvin Cycle) use that chemical energy to produce high-energy glucose from carbon dioxide and water. In the process, animals, including humans get food and an atmosphere filled with oxygen. Cellular Respiration Chapter 9 Review What is the equation for photosynthesis? What are the two reactions for photosynthesis? Where do they occur? Cellular Respiration Cellular Respiration is the process that releases energy from food in the presence of oxygen. Food molecules contain chemical energy that is released when its chemical bonds are broken. Energy stored in food is expressed in amount of calories. What is a calorie? The amount of energy needed to raise the tempearutre of 1 gram of water 1 Celsius degree. (the calories used in food labels is a kilocalorie, or 1,000 calories.) Overview of Cellular Respiration Location: Mitochondria (powerhouse of the cell) Purpose: Turn chemical energy (food) into usable energy (ATP) Chemical Equation: In symbols: C 6 H 12 O O 2 6 CO H 2 O In words: glucose + oxygen ---- carbon dioxide + water + Energy 3 stages of Cellular Respiration in order Glycolysis Krebs Cycle Electron Transport Chain Glycolysis (stage one) Means: Split glucose Reactants (Input): Glucose Products (Output): 2ATP and Pyruvates Note: pyruvates are often called pyruvic acid Glycolysis Glycolysis produces only a small amount of energy. Most of glucoses energy (90 %) remains locked in the chemical bonds of pyruvic acid at the end of glycolysis. Glycolysis is an anaerobic process. It does not directly require oxygen,nor does it rely on an oxygen-requiring process to run. Glycolysis takes place in the cytoplasm of the cell. Glycolysis What are the advantages of glycolysis? 1. process is fast 2. does not require oxygen Oxygen and Energy Pathways of cellular respiration that require oxygen are called aerobic. The Krebs Cycle and the Electron Transport chain are both aerobic processes. Both processes take place inside the mitochondria. Krebs or Citric Acid Cycle Reactant: Pyruvate and oxygen Product: 2ATP and CO 2 Other name?-The Citric Acid Cycle-citric acid is produced Electron Transport Chain Location: Mitochondria Reactant: Oxygen Oxygen acts as an electron receptor. Product: 32 ATP and H 2 O Energy Totals How many ATP molecules are made by cellular respiration? 36 Where do they come from (what stage?). 2 ATPs from glycolysis, 34 from the Krebs cycle and the Electron Transport Chain Sources besides glucose to generate ATP? 1. alcoholic fermentation 2. lactic acid fermentation 3. glycogen Relationship Opposite processes Relationship Photosynthesis is about energy capture where cellular respiration is about energy release. 36% of energy from glucose is given off as ATP which leaves 64% given off as heat. Comparing Photosynthesis and Cellular Respiration Reactants- Photosynthesis: Carbon Dioxide and Water Reactants-Cellular Respiration: glucose and oxygen Products-Photosynthesis: Glucose and Oxygen Products-Cellular Respiration: carbon dioxide, water and ATP Photosynthesis occurs in the chloroplast Cellular Respiration occurs in the mitochondria Review What is the equation for cellular respiration? What are the three reactions for cellular respiration? Where do they occur? What are all the inputs for cellular respiration? What are all the outputs for cellular respiration? What is the relationship between photosynthesis and cellular respiration? Fermentation What is fermentation? In the absence of oxygen there is no cellular respiration, fermentation occurs and small amounts of ATP (energy) will be created in order to keep the cell from dying. Where? The cytoplasm Two kinds of fermentation Lactic Acid Fermentation Alcoholic Fermentation Alcoholic Fermentation Produces alcohol, carbon dioxide, and 2 ATP Example: Bread/yeast: This process causes bread dough to rise and the carbon dioxide released causes the holes in bread. This is how alcoholic beverages are created. Lactic Acid Fermentation Produces lactic acid and 2 ATP Example: Muscle Cells: Fermentation occurs during heavy exercise Bacteria: Some help to make yogurt and cheese Energy/Exercise Quick Energy Cells normally contain small amounts of ATP produced during cellular respiration, enough for quick burst of intense activity. Lactic Acid Fermentation can supply enough ATP to last about 90 seconds. However, extra oxygen is reuqired to get rid of the lactic acid produced. Following intense exercise, a person will huff and puff for several minutes to pay back the built up oxygen- debt and clear the lactic acid from the body. Energy/Exercise Longer exercises Fermentation only makes enough energy to last 90 seconds Exercise longer than this can only get the energy it needs from cellular respiration. The body stores energy in the form of the carbohydrate glycogen. These glycogen stores are enough to last for 15 to 20 minutes of activity. After that, the body begins to break down other stored molecules, including fats, for energy. This is how animals can hibernate by living off of stored fats. Review When does fermentation occur? What are the two types of fermentation? For each type: What are the inputs? What are the outputs?