1. Inquiry into Life Twelfth Edition
Lecture PowerPoint to accompany
Inquiry into Life Twelfth Edition
Sylvia S. Mader
Chapter 6
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

2. 6.2 Metabolic Reactions and Energy Transformations

3. 6.2 Metabolic Reactions and Energy Transformations
Metabolism is the sum of all the chemical reactions that occur in a cell.

4. 6.2 Metabolic Reactions and Energy Transformations
Metabolism is the sum of all the chemical reactions that occur in a cell.
A + B C + D
(reactants) (products)

5. 6.2 Metabolic Reactions and Energy Transformations
Free energy (∆G) is the amount of energy available.

6. 6.2 Metabolic Reactions and Energy Transformations
Free energy (∆G) is the amount of energy available.
Exergonic reactions are ones where energy is released (∆G is negative)

7. 6.2 Metabolic Reactions and Energy Transformations
Free energy (∆G) is the amount of energy available.
Exergonic reactions are ones where energy is released (∆G is negative)
Endergonic reactions require an input of energy. (∆G is positive)

8. 6.2 Metabolic Reactions and Energy Transformations
ATP: Energy for Cells
ATP stands for adenosine triphosphate, the common energy currency for cells.

9. 6.2 Metabolic Reactions and Energy Transformations
ATP: Energy for Cells
ATP stands for adenosine triphosphate, the common energy currency for cells.
ATP is generated from ADP (adenosine diphosphate) + an inorganic phosphate molecule ( P )

10. The ATP Cycle

11. 6.2 Metabolic Reactions and Energy Transformations
Structure of ATP
ATP is a nucleotide that is composed of:
Adenine (a nitrogen-containing base)
Ribose (a 5-carbon sugar)
Three phosphate groups

12. 6.2 Metabolic Reactions and Energy Transformations
Structure of ATP
ATP is a “high energy” compound because a phosphate group can easily be removed.

13. 6.2 Metabolic Reactions and Energy Transformations
Coupled Reactions
The energy released by an exergonic reaction is used to drive an endergonic reaction.

14. Coupled Reactions

15. 6.3 Metabolic Pathways and Enzymes
Metabolic pathways are a series of linked reactions.
These begin with a specific reactant and produce an end product

16. 6.3 Metabolic Pathways and Enzymes
Enzymes are usually proteins that function to speed a chemical reaction.
Enzymes serve as catalysts

17. A Metabolic Pathway

18. 6.3 Metabolic Pathways and Enzymes
The Energy of Activation (Ea) is the energy that must be added to cause molecules to react with one another.

19. Energy of Activation

20. 6.3 Metabolic Pathways and Enzymes
How Enzymes Function
Enzyme binds substrate to form a complex
E + S  ES  E + P

21. Enzymatic Action

22. 6.3 Metabolic Pathways and Enzymes
How Enzymes Function
Enzyme binds substrate to form a complex
E + S  ES  E + P
Induced fit model
Substrate and active site shapes don’t match exactly
Active site is induced to undergo a slight change in shape to accommodate substrate binding

23. Induced Fit Model

24. 6.3 Metabolic Pathways and Enzymes
Factors Affecting Enzymatic Speed
Substrate Concentration
Temperature and pH
Enzyme Activation
Enzyme Inhibition
Enzyme Cofactors

25. 6.3 Metabolic Pathways and Enzymes
Substrate Concentration
Enzyme activity increases as substrate concentration increases because there are more collisions between substrate and enzyme
Maximum rate is achieved when all active sites of an enzyme are filled continuously with substrate

26. Metabolic Pathways and Enzymes
Temperature
Enzyme activity increase as temperature rises
Higher temperatures cause more effective collisions between enzymes and substrates
High temperatures may denature an enzyme, inhibiting its ability to bind to substrates

27. The Effect of Temperature on the Rate of Reaction

28. Metabolic Pathways and EnzymespH
Each enzyme has an optimal pH
Enzyme structure is pH dependent
Extremes of pH can denature an enzyme by altering its structure

29. Effect of pH on the Rate of Reaction

30. Metabolic Pathways and Enzymes
Enzyme Activation
Cell regulates metabolism by regulating which enzymes are active
Genes producing enzymes can be turned on or off to regulate enzyme concentration
In some cases a signaling molecule is used to activate an enzyme

31. Metabolic Pathways and Enzymes
Enzyme Inhibition
Occurs when enzyme cannot bind its substrate
Activity of cell enzymes is regulated by feedback inhibition
Ex: when product is abundant it binds to the enzyme’s active site and blocks further production
When product is used up, it is removed from the active site
In a more complex type of inhibition, product binds to a site other than the active site, which changes the shape of the active site
Poisons are often enzyme inhibitors

32. Feedback Inhibition

33. Metabolic Pathways and Enzymes
Enzyme Cofactors
Molecules which help enzyme function
Copper and zinc are examples of inorganic cofactors
Organic non-protein cofactors are called coenzymes
Vitamins are often components of coenzymes

34. 6.4 Oxidation-Reduction and the Flow of Energy
Oxidation is the loss of electrons
Reduction is the gaining of electrons
Ex: when oxygen combines with a metal like Mg, oxygen receives electrons (becomes negatively charged) and Mg loses electrons (becomes positively charged)
We say Mg has become oxidized, and oxygen is reduced (has a negative charge) when MgO forms

35. 6.4 Oxidation-Reduction and the Flow of Energy
The term oxidation is used even when oxygen is not involved
Ex: Na+ + Cl-  NaCl in which sodium is oxidized and chloride is reduced
This also applies to covalent reactions involving hydrogen atoms
Oxidation is the loss of hydrogen and reduction is the gain of hydrogen atoms

36. 6.4 Oxidation-Reduction and the Flow of Energy.
Photosynthesis
energy + 6CO2+6H2O C6H12O6 + 6O2
Hydrogen atoms are transferred from water to carbon dioxide and glucose is formed
Energy is required and this comes in the form of light energy from the sun
Chloroplasts convert solar energy to ATP which is then used along with hydrogen to reduce carbon dioxide to glucose

37. Oxidation-reduction and the flow of energy cont’d.
Cell Respiration
C6H12O6 + 6O2 6CO2 + 6H2O + energy
Glucose is oxidized (lost hydrogen atoms)
Oxygen is reduced to form water
Complete oxidation of a mole of glucose produces 686 kcal of energy
This energy is used to form ATP
The oxidation of glucose to form ATP is done is a series of small steps to increase efficiency

38. 6.4 Oxidation-Reduction and the Flow of Energy.
Organelles and the flow of energy
Cycling of molecules between chloroplasts and mitochondria allows energy to flow from sun to all living things
Chloroplasts use light energy from the sun to make carbohydrates
Mitochondria break down carbohydrates to form ATP
Cell respiration produces carbon dioxide and water which are used in photosynthesis

39. Relationship of Chloroplasts to Mitochondria