Chapter 9: Cellular Respiration

Transcription

1 Chapter 9: Cellular Respiration Breaking down glucose a little at a time.. It s like turning a five pound bag of sugar into several tiny sugar packets worth of energy in the form of ATP.

2 Remember the carbon cycle: the relationship between photosynthesis and cellular respiration

3 Section 9-1: Chemical Pathways What does food provide? Chemical building blocks for growth and reproduction Source of raw materials to make new molecules A source of energy

4 Chemical Energy & Food Food energy is measured in calories A calorie = the amount of energy needed to raise the temperature of 1 gram of water 1 degree Celsius

5 Chemical Energy & Food, cont d Calories (with a capital C) are used on food labels 1 Calorie = 1 kilocalorie = 1000 calories One gram of sugar releases 3811 calories of heat energy when burned in the presence of O 2

6 Overview of Cellular Respiration Cellular Respiration = a complex process that releases energy by breaking down glucose and other food molecules in the presence of oxygen The Overall Equation: C 6 H 12 O 6 + 6O 2 6CO H Energy glucose + oxygen carbon dioxide + water + energy

7 Overview of Cellular Respiration, cont d Q: What is the goal of cellular respiration? A: To release the energy stored in glucose in a series of small steps and store that released energy in ATP

8 An Overview of Cellular Respiration Three stages Glycolysis Krebs cycle Electron transport chain and oxidative phosphorylation.

9 Glycolysis The process in which one molecule of glucose, a 6-carbon compound, is broken in half to produce two molecules of pyruvic acid, a 3- carbon compound Note: pyruvate = pyruvic acid

10 Glycolysis, cont d Takes place in the cytoplasm Does not require oxygen Splitting one glucose leads to the formation of: 2 pyruvic acid 2 ATP (net gain) 2 NADH, an electron carrier

11 Glycolysis, cont d Occurs very quickly Can produce thousands of ATP molecules within a few seconds Needs a constant supply of NAD + or glycolysis stops

12 Fermentation Purpose is to regenerate NAD + so glycolysis can continue Occurs in the cytoplasm Occurs in the absence of oxygen (anaerobic) Two types: Alcoholic Fermentation Lactic Acid Fermentation

13 Alcoholic Fermentation pyruvic acid + NADH alcohol + CO 2 + NAD + Occurs in yeasts and a few other microorganisms Process that causes bread dough to rise Generates ethanol and carbon dioxide as products

14 Lactic Acid Fermentation pyruvic acid + NADH lactic acid + NAD + Occurs in muscles during rapid exercise Buildup of lactic acid causes a painful burning sensation Prokaryotes using lactic acid fermentation aid in the production of cheese, yogurt, and, sour cream

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16 Let s review mitochondrion structure before we begin to talk about cellular respiration in detail..

17 The mitochondrion, site of cellular respiration

18 Mitochondrion Structure Outer Membrane Inner Membrane (cristae) = site of electron transport chain Intermembrane Space = where H + accumulates in between the inner and outer membrane Matrix = the center of the mitochondria, Krebs cycle occurs here

19 Section 9-2 The Krebs Cycle & Electron Transport Glycolysis releases only 10% of the energy stored in glucose What happens to the other 90%? That energy is released via the Krebs cycle and the electron transport chain

20 Glycolysis Reviewed Remember that: Glycolysis takes place in the cytoplasm Splitting one glucose leads to the formation of: 2 pyruvic acid 2 ATP (net gain) 2 NADH, an electron carrier

21 The Krebs Cycle Before the Krebs cycle can begin pyruvic acid must move from the cytoplasm to the mitochondria During the crossing the following occurs per glucose: 2 pyruvic acid 2 CO 2 2 coenzyme A 2 acetyl CoA 2 NAD + 2 NADH

22 The intermediate reaction leads to the production of 2 Acetyl CoA & 2NADH & 2 CO 2 per glucose The Krebs Cycle leads to the production of CO 2, NADH, FADH 2 & ATP

23 The Krebs Cycle, cont d First step: 2 Acetyl CoA + 2 oxaloacetate 2 citric acid (2 carbon) + (4 carbon) (6 carbon) + 2 Coenzyme A Complicated series of steps continue on in the cycle

24 The Krebs Cycle, cont d At the end of 2 cycles needed per glucose: 2 citric acid 2 oxaloacetates 4 CO 2 6 NAD + 6 NADH 2 FAD 2 FADH 2 2 ADP 2 ATP

25 The Krebs Cycle, cont d What do you need to know? During the Krebs cycle: Pyruvic acid is completely broken down to CO 2 Most of the energy released during the cycle is stored in the electron carriers NADH and FADH 2 2 ATP are produced during the Krebs cycle

26 The Krebs Cycle, cont d Other things to note: Citric acid is produced in the first step so the Krebs cycle is also called the citric acid cycle Other substances such as fatty acids and amino acids can also enter the Krebs cycle and be broken down to release energy

27 Electron Transport Chain The electron transport chain uses the high energy electrons from NADH & FADH 2 to convert ADP to ATP In eukaryotes electron transport occurs at the inner membrane of a mitochondrion

28 Electron Transport Hydrogen Ion Movement ATP synthase Intermembrane Space Inner Membrane Matrix ATP Production

29 Electron Transport As high energy electrons move down the electron transport chain, the released energy is used to drive the movement of H + into the intermembrane space H + then moves down its concentration gradient through ATP synthase ADP is converted to ATP by ATP synthase

30 Electron Transport, cont d O 2 is the final electron acceptor Oxygen picks up electrons and H + and is converted into water Without O 2, there would be a traffic jam of backed up electrons and cellular respiration would cease

31 ATP Structure, a review Adenosine triphosphate = ATP ATP consists of: adenine ribose (a 5 carbon sugar) & three phosphates

32 The ADP ATP Cycle P Cellular Respiration or the Light Reactions Photosynthesis ATP ADP Cellular Work or the Calvin Cycle of Photosynthesis P

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34 Electron Carriers & ATP Production Each NADH leads to the production of 3 ATP Each FADH 2 leads to the production of 2 ATP The only exception seems to be the NADH from glycolysis which leads to formation of 2 ATP per NADH

35 Summary of ATP Production per Glucose Molecule Glycolysis 2 ATP 2 NADH 4 ATP Intermediate 2 NADH 6 ATP Reaction to make acetyl CoA Krebs Cycle 2 ATP 6NADH 18ATP 2 FADH 2 4 ATP 36 Total ATP

36 Energy & Exercise Where does your body get the energy needed for exercise? First your body uses the small stores of ATP normally found in a cell / there is enough stored ATP to allow a few seconds of intense activity Second your body turns to lactic acid fermentation which produces enough ATP to last about 90 seconds

37 Energy & Exercise If exercise lasts longer than 90 seconds, cellular respiration must be used to generate sufficient ATP Glycogen stores in the liver and muscle are broken down to glucose / can provide enough energy for minutes of intense activity After glycogen stores are depleted after 20 minutes, body turns to fat as the fuel / fatty acids enter the Krebs cycle in the form of acetyl CoA

38 Comparing Photosynthesis & Cellular Respiration See handouts/graphic organizers Photosynthesis deposits or stores energy occurs in plants Cellular Respiration withdraws or releases energy occurs in both plant and animal cells

39 The Carbon Cycle A strong cyclic relationship exists between photosynthesis and cellular respiration Photosynthesis 6CO H 2 0 C 6 H 12 O 6 + 6O 2 Cellular Respiration C 6 H 12 O 6 + 6O 2 6CO H 2 0

40 The carbon cycle Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig

41 Analyzing Experimental Set-Ups Do you understand the set-up? Can you identify the proper controls? Can you identify what is being asked for? Can you make predictions as to what the expected results might be based on prior knowledge?

42 Electron Carriers, cont d NAD + + H + + 2e - NADH FAD + + 2H + + 2e - FADH 2