Cool “Fires” Attract Mates and Meals

1. Cool “Fires” Attract Mates and Meals • Fireflies use light to signal to potential mates • attract males of other species — as meals • luciferin-luciferase system

2. Energy and cells • What is energy? Why do we need it? • How do chemical reactions use or produce energy? • How does ATP transfer energy? • How do enzymes affect rates of chemical reactions?

3. Energy is the capacity to perform work

4. Rearrangement of atoms will either store or release energychemical reaction = rearrangement of atoms Chemical energy is due to the arrangement of atoms in molecules

5. Endergonic reactions absorb energy and yield products rich in potential energy Products Amount of energy INPUT Potential energy of molecules Reactants Figure 5.3A

6. Exergonic reactions release energy and yield products that contain less potential energy than their reactants Reactants Amount of energy OUTPUT Potential energy of molecules Products Figure 5.3B

7. Energy content of common chemicals (foods) Energy used in activities

8. ATP shuttles chemical energy within the cell • In cellular respiration, some energy is stored in ATP molecules • ATP powers nearly all forms of cellular work • ATP is key to energy coupling

9. This reaction supplies energy for cellular work: Adenine Phosphategroups Hydrolysis Energy Ribose Adenosine triphosphate Adenosine diphosphate(ADP) Figure 5.4A

10. Fig. 5.8

11. Enzymes lower energy barriers How do enzymes work? • For a chemical reaction to begin, reactants must absorb some energy • energy of activation (EA) = energy barrier

12. enzymes can decrease the energy barrier EA barrier Enzyme Reactants 1 Products 2 Figure 5.5A

13. Activesite Enzyme(sucrase) • enzyme is unchanged and can repeat the process Substrate(sucrose) Glucose Fructose 1 4 Enzyme available with empty active site Products are released 3 A specific enzyme catalyzes each cellular reaction 2 Substrate is converted to products Substrate binds to enzyme with induced fit Figure 5.6

14. The cellular environment affects enzyme activity • Enzyme activity is influenced by • temperature • salt concentration • pH • Reaction rate is affected by amount of substrate • Allosteric regulation by other factors

15. Some enzymes require nonprotein cofactors • Ex. zinc, iron • coenzymes = cofactors that are organic molecules • Ex. vitamins

16. A. Cellular respiration • Glycolysis • Kreb cycle • Electron transport chain B. Fermentation

17. Cellular respiration breaks down glucose molecules and banks their energy in ATP • uses O2 and releases CO2 and H2O Glucose Oxygen gas Carbon dioxide Water Energy

18. Redox reactions are linked oxidations and reductions • Glucose gives up energy as it is oxidized oxidation = loss of H Oxygen is reduced (gains H) Loss of hydrogen atoms Energy Glucose Gain of hydrogen atoms Figure 6.4

19. High-energy electrons carried by NADH • An overview of cellular respiration GLYCOLYSIS ELECTRONTRANSPORT CHAINAND CHEMIOSMOSIS KREBSCYCLE Glucose Pyruvicacid Cytoplasmicfluid Mitochondrion Figure 6.8

20. Glycolysis harvests chemical energy by oxidizing glucose to pyruvic acid Glucose Pyruvicacid Figure 6.9A

21. Pyruvic acid is chemically groomed for the Kreb cycle • Each pyruvic acid molecule is broken down to form CO2 and a two-carbon acetyl group, which enters the Kreb cycle Pyruvicacid Acetyl CoA(acetyl coenzyme A) CO2 Figure 6.10

22. The Kreb cycle completes the oxidation of organic fuel Acetyl CoA • enzymes strip away electrons and H+ from each acetyl group, generating many NADH and FADH2 molecules 2 KRESCYCLE CO2 Figure 6.11A

23. Proteincomplex • Electron Transport System and chemiosmosis in the mitochondrion Intermembranespace Electroncarrier Innermitochondrialmembrane Electronflow Mitochondrialmatrix ELECTRON TRANSPORT CHAIN ATP SYNTHASE Figure 6.12

24. cell outer membrane inner membrane mitochondrion

25. inner membrane glycolysis outer membrane H+ H+ H+ H+ H+ electron transport chain Krebs cycle H+ H+ H+ H+ e- O2 outer compartment H2O inner compartment

26. : Certain poisons interrupt critical events in cellular respiration Rotenone Oligomycin Cyanide,carbon monoxide ELECTRON TRANSPORT CHAIN ATP SYNTHASE Figure 6.13

27. High-energy electrons carried by NADH • An overview of cellular respiration GLYCOLYSIS ELECTRONTRANSPORT CHAINAND CHEMIOSMOSIS KREBSCYCLE Glucose Pyruvicacid Cytoplasmicfluid Mitochondrion Figure 6.8

28. Fermentation is an anaerobic alternative to aerobic respiration • Without oxygen, cells can use glycolysis alone to produce small amounts of ATP • But a cell must replenish NAD+ Glucose Pyruvicacid

29. This recycles NAD+ to keep glycolysis working • In alcoholic fermentation, pyruvic acid is converted to CO2 and ethanol FERMENTATION GLYCOLYSIS released 2 Pyruvicacid 2 Ethanol Glucose Figure 6.15C

30. NAD+ is recycled • Produces cheese and yogurt • In lactic acid fermentation, pyruvic acid is converted to lactic acid GLYCOLYSIS 2 Pyruvicacid 2 Lactic acid Glucose Figure 6.15B

31. Cells use many kinds of organic molecules as fuel for cellular respiration • Polysaccharides monosaccharides glucose for glycolysis • Proteins amino acids Krebs cycle • Fats acetyl-Co A Krebs cycle

32. Food, such as peanuts • Pathways of molecular breakdown Polysaccharides Fats Proteins Sugars Glycerol Fatty acids Amino acids Amino groups Pyruvicacid ELECTRONTRANSPORT CHAINAND CHEMIOSMOSIS Glucose G3P AcetylCoA KREBSCYCLE GLYCOLYSIS Figure 6.16

33. Food molecules provide raw materials for biosynthesis • cells need raw materials for growth and repair • Some directly from food • Others made from intermediates in glycolysis and the Krebs cycle • Biosynthesis uses ATP (endergonic)

34. ATP needed todrive biosynthesis • Biosynthesis of macromolecules from intermediates in cellular respiration GLUCOSE SYNTHESIS KREBSCYCLE AcetylCoA Pyruvicacid G3P Glucose Aminogroups Amino acids Fatty acids Glycerol Sugars Proteins Fats Polyscaccharides Cells, tissues, organisms Figure 6.17