Biology 2201 Unit 1 Matter & Energy for Life

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Liliana Owens
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1 Biology 2201 Unit 1 Matter & Energy for Life 3.3 Cellular Respiration 3.4 The Carbon Cycle What is cellular respiration? Cellular respiration all of the chemical reactions needed to break down (metabolize) carbohydrates and other molecules to transfer chemical energy to ATP. The food that most organisms consume has to be broken down so energy can be released. However, the energy that comes from food has to be stored and transported to cells which need the energy (like muscle cells). Energy is temporarily stored in most living things in a molecule called ATP. 1

2 What is ATP? Adenosine Triphosphate A high energy compound found within cells Composed of a molecule of adenosine and three molecules of phosphate. The phosphates are held to the adenosine by high energy bonds The bonds break, releasing energy along with ADP (adenosine diphosphate) and a phosphate The ATP acts as the intermediary between energy releasing (exergonic) and energy requiring (endergonic) reactions in the cell ATP ADP Cycle When energy needs to be stored, ADP (adenosine diphosphate) is converted to ATP by adding a phosphate group with a high energy bond. When energy needs to be released in a cell, ATP is broken down to ADP, breaking the highenergy bond. 2

3 ATP ADP Cycle diagram Types of Cellular Respiration Two types of cellular respiration: (1) aerobic (2) anaerobic 3

4 Aerobic Cellular Respiration requires the presence of oxygen essentially the reverse of photosynthesis C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O + ATP 4 main phases (see fig. 3.15, p. 83) 1) Glycolysis One glucose is broken down into 2 pyruvate molecules 2 ATP are produced and 2 carrier molecules occurs in the cytoplasm of cells 2) transition reaction pyruvate molecules are converted to CO 2 molecules and acetyl coenzyme A (acetyl CoA) no ATP produced directly but 2 carrier molecules are occurs in the cytoplasm of cells Aerobic Cellular Respiration (cont...) 3) Krebs cycle Produces carrier molecules for the electron transport chains Occurs in the mitochondria 2 ATP produced directly 4) Electron transport chain Produces the majority of ATP Occurs inside the mitochondria Carrier molecules pass electrons from carrier to the next and finally to oxygen. The passing of electrons produces a lot of ATP (32 in total) By the end of aerobic cellular respiration, 36 ATP are produced from one glucose molecule. 4

5 Anaerobic cellular respiration occurs in the absence of oxygen does not produce much energy, only 2 ATP per glucose molecule has only 2 stages: 1) Glycolysis Same as aerobic, a glucose gets converted to 2 pyruvate molecules 2) Fermentation Pyruvate molecules converted to a form where no more energy can be extracted Different fermentation products in different organisms o In humans, fermentation can occur in muscle cells producing lactic acid o In yeast, fermentation leads to the production of ethanol (grain alcohol) and eventually acetic acid (vinegar) The Carbon Cycle Respiration and photosynthesis are dependant upon each other Two halves of the carbon cycle Photosynthesis produces the raw materials for respiration, and respiration produces the raw materials for photosynthesis 5

6 The Carbon Cycle (diagram) How Do we Affect the Carbon Cycle? Ways in which we affect the carbon cycle: Agriculture Clear cutting Mining Burning fossil fuels (See page 88 in textbook) Each of these has an overwhelming effect on the levels of carbon available for cycling All of which add carbon to the atmosphere, affecting levels stored in biotic sources (plants / animals) 6

ADP, ATP and Cellular Respiration

ADP, ATP and Cellular Respiration What Is ATP? Energy used by all Cells Adenosine Triphosphate Organic molecule containing highenergy Phosphate bonds Chemical Structure of ATP Adenine Base 3 Phosphates