Copyright Pearson Prentice Hall Biology Copyright Pearson Prentice Hall

Energy and Life EQ What are photosynthesis and cellular respiration? Photo Credit: ©Stone Copyright Pearson Prentice Hall

Autotrophs and Heterotrophs Living things need energy to survive. This energy comes from food. The energy in most food comes from the sun. Where do plants get the energy they need to produce food? Copyright Pearson Prentice Hall

Autotrophs and Heterotrophs Plants and some other types of organisms are able to use light energy from the sun to produce food are called autotrophs. Organisms that obtain their energy from the food they eat are called heterotrophs. Copyright Pearson Prentice Hall

Chemical Energy and ATP Energy comes in many forms including light, heat, and electricity. Energy can also be stored in chemical compounds. Copyright Pearson Prentice Hall

Chemical Energy and ATP An important chemical compound that cells use to store and release energy is adenosine triphosphate, abbreviated ATP. ATP is used by all types of cells as their basic energy source. Copyright Pearson Prentice Hall

Chemical Energy and ATP ATP consists of: adenine ribose (a 5-carbon sugar) 3 phosphate groups Adenine Ribose 3 Phosphate groups ATP is used by all types of cells as their basic energy source. ATP Copyright Pearson Prentice Hall

Chemical Energy and ATP Storing Energy ADP has two phosphate groups instead of three. A cell can store small amounts of energy by adding a phosphate group to ADP. ATP ADP Energy + Energy Adenosine Triphosphate (ATP) Adenosine Diphosphate (ADP) + Phosphate Partially charged battery Fully charged battery Copyright Pearson Prentice Hall

Chemical Energy and ATP Releasing Energy Energy stored in ATP is released by breaking the chemical bond between the second and third phosphates. 2 Phosphate groups P ADP Copyright Pearson Prentice Hall

Chemical Energy and ATP The energy from ATP is needed for many cellular activities, including active transport across cell membranes, protein synthesis and muscle contraction. ATP’s characteristics make it exceptionally useful as the basic energy source of all cells. Copyright Pearson Prentice Hall

Using Biochemical Energy Most cells have only a small amount of ATP, because it is not a good way to store large amounts of energy. Cells can regenerate ATP from ADP as needed by using the energy in foods like glucose. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall The key cellular process identified with energy production is photosynthesis. Photosynthesis is the process in which green plants use the energy of sunlight to convert water and carbon dioxide into high-energy carbohydrates and oxygen. Copyright Pearson Prentice Hall

The Photosynthesis Equation The equation for photosynthesis is: CO2 + H2O C6H12O6 + O2 carbon dioxide + water sugars + oxygen Light Light Copyright Pearson Prentice Hall

The Photosynthesis Equation Photosynthesis uses the energy of sunlight to convert water and carbon dioxide into high-energy sugars and oxygen. Copyright Pearson Prentice Hall

The Photosynthesis Equation Light energy H2O Light-Dependent Reactions (thylakoids) O2 ADP NADP+ ATP NADPH Photosynthesis is a series of reactions that uses light energy from the sun to convert water and carbon dioxide into sugars and oxygen. CO2 + H20 Sugar Calvin Cycle (stroma) Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Light and Pigments Light and Pigments How do plants capture the energy of sunlight? In addition to water and carbon dioxide, photosynthesis requires light and chlorophyll. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Light and Pigments Plants gather the sun's energy with light-absorbing molecules called pigments. The main pigment in plants is chlorophyll. There are two main types of chlorophyll: chlorophyll a chlorophyll b Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Light and Pigments Chlorophyll does not absorb light will in the green region of the spectrum. Green light is reflected by leaves, which is why plants look green. 100 80 60 40 20 Chlorophyll b Estimated Absorption (%) Chlorophyll a Photosynthesis requires light and chlorophyll. In the graph above, notice how chlorophyll a absorbs light mostly in the blue-violet and red regions of the visible spectrum, whereas chlorophyll b absorbs light in the blue and red regions of the visible spectrum. 400 450 500 550 600 650 700 750 Wavelength (nm) Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 9-1 Chemical Pathways Food serves as a source of raw materials for the cells in the body and as a source of energy. Animal Cells Animal Mitochondrion Plant Photo Credits: left: ©Bob Gurr/DRK Photo; middle bottom: ©John Durham/Science Photo Library/Photo Researchers, Inc. ; middle top: ©Ron Boardman/Stone; right: ©Keith Porter/Photo Researchers, Inc. Plant Cells Copyright Pearson Prentice Hall

Overview of Cellular Respiration Cellular respiration is the process that releases energy by breaking down glucose and other food molecules in the presence of oxygen. Copyright Pearson Prentice Hall

Overview of Cellular Respiration The equation for cellular respiration is: 6O2 + C6H12O6 → 6CO2 + 6H2O + Energy oxygen + glucose → carbon dioxide + water + Energy Copyright Pearson Prentice Hall

Overview of Cellular Respiration Glycolysis takes place in the cytoplasm. The Krebs cycle and electron transport take place in the mitochondria. Glycolysis Cellular respiration is the process that releases energy by breaking down food molecules in the presence of oxygen. Glycolysis takes place in the cytoplasm. The Krebs cycle and electron transport take place inside the mitochondria. Cytoplasm Mitochondrion Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Glycolysis ATP Production At the beginning of glycolysis, the cell uses up 2 molecules of ATP to start the reaction. 2 ATP 2 ADP 4 ADP 4 ATP Glycolysis is the first stage in cellular respiration. During glycolysis, glucose is broken down into 2 molecules of pyruvic acid. Glucose 2 Pyruvic acid Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Glycolysis Four molecules of ATP are produced. This gives the cell a net gain of 2 ATP molecules. 2 ATP 2 ADP 4 ADP 4 ATP Glucose 2 Pyruvic acid Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Glycolysis One reaction of glycolysis removes 4 high-energy electrons, passing them to an electron carrier called NAD+. Each NAD+ accepts a pair of high-energy electrons and becomes an NADH molecule. 2 ATP 2 ADP 4 ADP 4 ATP Glucose 2NAD+ 2 Pyruvic acid 2 Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Glycolysis The Advantages of Glycolysis The process of glycolysis is so fast that cells can produce thousands of ATP molecules in a few milliseconds. Glycolysis does not require oxygen. Copyright Pearson Prentice Hall

9-2 The Krebs Cycle and Electron Transport Oxygen is required for the final steps of cellular respiration. Because the pathways of cellular respiration require oxygen, they are aerobic. During the Krebs cycle, pyruvic acid is broken down into carbon dioxide in a series of energy-extracting reactions. The energy tally from 1 molecule of pyruvic acid is 4 NADH 1 FADH2 1 ATP Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall The Totals The Totals Glycolysis produces just 2 ATP molecules per molecule of glucose. The complete breakdown of glucose through cellular respiration, including glycolysis, results in the production of 36 molecules of ATP. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall The Totals The complete breakdown of glucose through cellular respiration, including glycolysis, results in the production of 36 molecules of ATP. Copyright Pearson Prentice Hall

Comparing Photosynthesis and Cellular Respiration The energy flows in photosynthesis and cellular respiration take place in opposite directions. Copyright Pearson Prentice Hall

Comparing Photosynthesis and Cellular Respiration On a global level, photosynthesis and cellular respiration are also opposites. Photosynthesis removes carbon dioxide from the atmosphere and cellular respiration puts it back. Photosynthesis releases oxygen into the atmosphere and cellular respiration uses that oxygen to release energy from food. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Left Side Activity Write down the equations for photosynthesis and cellular respiration Explain how photosynthesis and cellular respiration are related Copyright Pearson Prentice Hall