Autotrophs and Heterotrophs

Transcription

1 8-1 Energy and Life 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? 1

2 Autotrophs and Heterotrophs Autotrophs and Heterotrophs Plants and some other types of organisms are able to use light energy from the sun to produce food. Autotrophs and Heterotrophs The study of energy is called thermodynamics. 2

3 Autotrophs and Heterotrophs There are 2 Laws of Thermodynamics: First Law: Energy cannot be created nor destroyed..it simply changes from one form to another. Second Law: Each time an energy change occurs, some energy is lost as heat energy. Autotrophs and Heterotrophs Organisms, such as plants, which make their own food, are called autotrophs. Organisms, such as animals, that must obtain energy from the foods they consume are heterotrophs. 3

4 Chemical Energy and ATP Chemical Energy and ATP Energy comes in many forms including light, heat, and electricity. Energy can be stored in chemical compounds, too. Chemical Energy and ATP A chemical compound that cells use to store and release energy is adenosine triphosphate, (ATP). ATP is used by all types of cells as their basic energy currency. 4

5 Chemical Energy and ATP ATP consists of: adenine ribose (a 5-carbon sugar) 3 phosphate groups Adenine Ribose 3 Phosphate groups ATP Chemical Energy and ATP The three phosphate groups are the key to ATP's ability to store and release energy. 5

6 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. ADP ATP Adenosine Diphosphate (ADP) + Phosphate Partially charged battery + Energy Energy Fully charged battery Adenosine Triphosphate (ATP) 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 6

7 Chemical Energy and ATP What is the role of ATP in cellular activities? 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. 7

8 Using Biochemical Energy 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. Notice that energy is REQUIRED to regenerate ATP from ADP and phosphate

9 8-1 Organisms that make their own food are called autotrophs. heterotrophs. decomposers. consumers. 8-1 Most autotrophs obtain their energy from chemicals in the environment. sunlight. carbon dioxide in the air. other producers. 9

10 8-1 How is energy released from ATP? A phosphate is added. An adenine is added. A phosphate is removed. A ribose is removed. 8-1 How is it possible for most cells to function with only a small amount of ATP? Cells do not require ATP for energy. ATP can be quickly regenerated from ADP and P. Cells use very small amounts of energy. ATP stores large amounts of energy. 10

11 8-1 Compared to the energy stored in a molecule of glucose, ATP stores much more energy. much less energy. about the same amount of energy. more energy sometimes and less at others. END OF SECTION 11

12 Photosynthesis Standard 3.1 Summarize the overall process by which photosynthesis converts solar energy into chemical energy and interpret the chemical equation for the process. Key Concepts: Photosynthesis: Light dependent reactions, light independent reactions Photosynthesis The ultimate source of all energy on earth is the sun. Photosynthesis is the overall process by which sunlight (solar energy) chemically converts water and carbon dioxide into chemical energy stored in simple sugars (glucose). 12

13 Photosynthesis The process of photosynthesis occurs in two stages: Light Dependent Reactions (light reactions) Light Independent Reactions (dark reactions) Light Dependent Reactions Require light Solar energy absorbed by chloroplasts ATP is produced NADPH is produced Both ATP and NADPH are energy storing molecules which are made in the light dependent reactions and then will be used in the light independent reactions. 13

14 Light Dependent Reactions The solar energy is used to split water molecules which results in the release of oxygen as a waste product. This is an essential step in photosynthesis. The hydrogen from the water molecule is then split into hydrogen protons and hydrogen electrons. Light Independent Reactions The second stage of photosynthesis. Sometimes called dark reactions because they do not require light directly. Also called the Calvin Cycle. The cycle was discovered by Melvin Calvin and his associates. He won a Nobel Prize for the discovery. 14

15 Light Independent Reactions Use the energy stored in ATP and NADPH to produce simple sugars (such as glucose) from carbon dioxide. These simple sugars are used to store chemical energy for use by the cells at later times. Products of Photosynthesis The simple sugars such as glucose may be used as an energy source through the process of cellular respiration or it can be converted to organic molecules (such as proteins, carbohydrates, fats/lipids, or cellulose) by various biological processes. 15

16 Balanced Photosynthesis Equation 6CO 2 + 6H 2 O + Solar energy C 6 H 12 O 6 + 6O 2 What this says is that 6 molecules of carbon dioxide + 6 molecules of water + light from the sun or some other source will react in the chloroplast to form one molecule of glucose + 6 molecules of oxygen. Basics to know about the process! In general six carbon dioxide molecules and six water molecules are needed to produce one glucose molecule and six oxygen molecules. Each of the reactants (carbon dioxide and water) is broken down at different stages of the process. Each of the products (oxygen and glucose) is formed in different stages of the process. Solar energy is needed to break down the water molecules. 16

17 Standard B 3.2 Summarize the basic aerobic and anaerobic processes of cellular respiration and interpret the chemical equation for cellular respiration. Standard B 3.2 Key Concepts: Cellular respiration Glycolysis Krebs Cycle (citric acid cycle) Anaerobic respiration lactic acid fermentation ATP, Aerobic respiration, electron transport chain, fermentation, alcoholic fermentation 17

18 Cellular Respiration The ultimate goal of cellular respiration is to convert the chemical energy in nutrients (food) to chemical energy stored in adenosine triphosphate (ATP). Food Energy Cellular Respiration ATP then releases the energy for cellular metabolic processes, such as active transport across cell membranes, protein synthesis, and muscle contraction. 18

19 Cellular Respiration Any food (organic) molecule, or nutrient, including carbohydrates, fats/lipids, and proteins can be processed and broken down as a source of energy to produce ATP molecules. Cellular Respiration Nutrients + oxygen water + energy (ATP) + carbon dioxide C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O + Energy (ATP) 19

20 Cellular Respiration To transfer the energy stored in glucose to the ATP molecules, a cell must break down glucose slowly to capture the energy in stages. Glycolysis The first stage is glycolysis. In the process of glycolysis, a glucose molecule is broken down into pyruvic acid (pyruvate) molecules and ATP molecules. Glycolysis takes place in a series of reactions using enzymes. Glycolysis takes place in the cytoplasm of the cell. 20

21 Glycolysis Glycolysis breaks glucose, a 6 carbon compound, (the usual starting sugar) down into two molecules of a 3 carbon compound which is known as pyruvate or pyruvic acid. Glycolysis In order for glycolysis to occur, two molecules of ATP must be invested. By the end of glycolysis, four molecules of ATP have been made, but only two are available to do work since the two molecules of ATP used to get started must be paid back. 21

22 Cellular Respiration The next stages depend on the presence of oxygen: Aerobic respiration uses oxygen when oxygen is present. Anaerobic respiration does not use oxygen. Cellular Respiration If oxygen is available, the next stage is aerobic respiration. Aerobic respiration takes place in the mitochondria of the cell. Aerobic respiration is a two step process The first step of aerobic respiration is called the citric acid cycle or Krebs cycle (named for Hans Krebs who described it). 22

23 Krebs Cycle The pyruvic acid formed in glycolysis travels to the mitochondria where it is chemically transformed in a series of steps, releasing carbon dioxide, water, and energy (which is used to form 2 ATP molecules) Pyruvic acid carbon dioxide + water + energy (ATP) The carbon dioxide is released as a waste product. Electron Transport Chain The second step of aerobic respiration is the electron transport chain. Most of the energy storing ATP molecules are formed during this part of the cycle. The electron transport chain is a series of chemical reactions ending with hydrogen combining with oxygen to form water. 23

24 Cellular Respiration Each reaction produces a small amount of energy, which by the end of the cycle produces many (up to 36) ATP molecules. The ATP synthesized can be used by the cell for cellular metabolism. (This means to carry out all functions of the cell and/or organism.) Cellular Respiration This is the balanced equation for cellular respiration using oxygen. C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O + energy In general, one glucose molecule and six oxygen molecules are needed to produce six carbon dioxide molecules and six water molecules. 24

25 Cellular Respiration Each of the reactants (glucose and oxygen) is used during different stages of aerobic respiration. Each of the products (carbon dioxide and water) is formed during different stages of the process. The energy released is primarily used to produce approximately 34 to 36 ATP per glucose molecule. Cellular Respiraiton If no oxygen is available, cells can obtain energy through the process of anaerobic respiration. A common anaerobic process is fermentation. Fermentation is not an efficient process and results in the formation of far fewer ATP molecules than aerobic respiration. 25

26 Cellular Respiration There are two primary fermentation processes: Lactic acid fermentation Alcoholic fermentation Cellular Respiration Lactic Acid Fermentation occurs when oxygen is NOT available, for example in muscle tissues during rapid and vigorous exercise when muscle cells may be depleted of oxygen. The pyruvic acid formed during glycolysis is broken down to lactic acid (lactate), and in the process energy is released to form ATP. 26

27 Cellular Respiration Glucose pyruvic acid lactic acid + energy The process of lactic acid fermentation replaces the process of aerobic respiration so that the cell can continue to have a continual source of energy (ATP) even in the absence of oxygen. Cellular Respiration The shift to lactic acid fermentation is only temporary and cells need oxygen for sustained activity. Lactic acid that builds up in the tissue causes a burning, painful sensation and eventually muscle fatigue. 27

28 Cellular Respiration Alcoholic fermentation occurs in yeasts and some bacteria. In the process of alcoholic fermentation, pyruvic acid formed during glycolysis is broken down to produce alcohol and carbon dioxide, and in the process energy is released in the form of ATP. Cellular Respiration Glucose pyruvic acid alcohol + carbon dioxide + energy Notice that carbon dioxide is given off as well as energy. That is why yeast is used in baking to make the dough rise. It is the gas, carbon dioxide, which causes the dough to rise. The alcohol is evaporated when the break is baked. 28

29 Some other tidbits about Cell Respiration. Glycolysis produces a total of 4 ATP, but 2 are used in the process so therefore a net of 2 ATP per glucose molecule. Krebs cycle produces 2 ATP per glucose molecule. The electron transport chain produces about 32 ATP The grand total of ATP is about ATP Some other tidbits continued: Aerobic respiration (using oxygen) provides about 34 to 36 ATP per molecule of glucose. Anaerobic respiration (not using oxygen) provides only 2 ATP. These 2 ATP come from glycolysis which is a part of both aerobic and anaerobic respiraiton. 29

30 Glycolysis takes place in the cytoplasm. Krebs cycle and electron transport chain both take place in mitochondria. In bacteria Krebs and electron transport will take place along the plasma membrane. Comparison of photosynthesis and cellular respiration. Photosynthesis: carbon dioxide + water are combined to form glucose + oxygen. Cellular respiration: glucose + oxygen are combined to form carbon dioxide + water. 30

31 Photosynthesis/Cellular Respiration The balanced equations seem to be the reverse of each other. Photosynthesis makes the glucose and other sugars which are the building blocks of the food for cellular respiration to break down. Photosynthesis/Cellular Respiration The ATP made during photosynthesis is used during photosynthesis. The ATP made during cellular respiration is used to power ALL CELLULAR PROCESSES. 31

32 Photosynthesis/Cellular Respiration Plants, some bacteria, and some protists carry out photosynthesis. ALL organisms (plants, animals, fungi, protists, bacteria) carry out cellular respiration. Comparison of photosynthesis and cellular respiration. Photosynthesis is Anabolic means to build up. Cellular respiration is Catabolic means to break down. 32