Introduction to Metabolism

1. Chapter 8 Warm-Up • Define the term “metabolism”. • List 3 forms of energy. • Where does the energy available for nearly all living things on earth come from?

2. Ch. 8 Warm-Up • What are the 1st and 2nd laws of thermodynamics? • Give the definition and an example of: • Catabolic reaction • Anabolic reaction • Is the breakdown of glucose in cellular respiration exergonic or endergonic?

3. Ch. 8 Warm-Up • Draw and label the following: enzyme, active site, substrate. • Describe what is meant by the term induced fit. • What types of factors can affect an enzyme’s function?

4. Chapter 8 An Introduction to Metabolism

5. What You Need To Know: • Examples of endergonic and exergonic reactions. • The key role of ATP in energy coupling. • That enzymes work by lowering the energy of activation. • The catalytic cycle of an enzyme that results in the production of a final product. • The factors that influence enzyme activity.

6. Metabolism is the totality of an organism’s chemical reactions • Manage the materials and energy resources of a cell

7. Catabolic pathwaysrelease energy by breaking down complex molecules into simpler compounds • Eg. digestive enzymes break down food  release energy • Anabolic pathwaysconsume energy to build complex molecules from simpler ones • Eg. amino acids link to form muscle protein

8. Energy = capacity to do work • Kinetic energy (KE): energy associated with motion • Heat (thermal energy) is KE associated with random movement of atoms or molecules • Potential energy (PE): stored energy as a result of its position or structure • Chemical energy is PE available for release in a chemical reaction • Energy can be convertedfrom one form to another • Eg. chemical  mechanical  electrical

10. Thermodynamics is the study of energy transformations that occur in nature • A closedsystem, such as liquid in a thermos, is isolated from its surroundings • In an opensystem, energy and matter can be transferred between the system and its surroundings • Organisms are open systems

11. The First Law of Thermodynamics • The energy of the universe is constant • Energy can be transferred and transformed • Energy cannot be created or destroyed • Also called the principle of Conservation of Energy

12. The Second Law of Thermodynamics • Every energy transfer or transformation increases the entropy (disorder) of the universe • During every energy transfer or transformation, some energy is unusable, often lost as heat

13. Free energy: part of a system’s energy available to perform work • G = change in free energy • Exergonic reaction: energy is released • Spontaneous reaction • G < 0 • Endergonic reaction: energy is required • Absorb free energy • G > 0

16. A cell does three main kinds of work: • Mechanical • Transport • Chemical • Cells manage energy resources to do work by energy coupling: using an exergonic process to drive an endergonic one

17. ATP (adenosine triphosphate) is the cell’s main energy source in energy coupling • ATP = adenine + ribose + 3 phosphates

18. When the bonds between the phosphate groups are broken by hydrolysis  energy is released • This release of energy comes from the chemical change to a state of lower free energy, not in the phosphate bonds themselves

19. How ATP Performs Work • Exergonic release of Pi is used to do the endergonic work of cell • When ATP is hydrolyzed, it becomes ADP (adenosine diphosphate)

20. P i P Protein moved Motor protein Mechanical work: ATP phosphorylates motor proteins Membrane protein ADP ATP + P i P P i Solute transported Solute Transport work: ATP phosphorylates transport proteins P NH2 NH3 P + + Glu i Glu Reactants: Glutamic acid and ammonia Product (glutamine) made Chemical work: ATP phosphorylates key reactants

21. Catalyst: substance that can change the rate of a reaction without being altered in the process • Enzyme= biological catalyst • Speeds up metabolic reactions by lowering the activation energy(energy needed to start reaction)

23. Substrate Specificity of Enzymes • The reactant that an enzyme acts on is called the enzyme’s substrate • The enzyme binds to its substrate, forming an enzyme-substrate complex • The active site is the region on the enzyme where the substrate binds

27. Enzyme Action: Catabolism

28. Enzyme Action: Anabolism

29. INDUCED FIT: ENZYME FITS SNUGLY AROUND SUBSTRATE -- “CLASPING HANDSHAKE”

30. An enzyme’s activity can be affected by: • temperature • pH • chemicals

31. Cofactors • Cofactorsare nonprotein enzyme helpers such as minerals (eg. Zn, Fe, Cu) • Coenzymesare organic cofactors (eg. vitamins) Enzyme Inhibitors • Competitive inhibitor: binds to the active siteof an enzyme, competes with substrate • Noncompetitive inhibitor: binds to another partof an enzyme  enzyme changes shape  active site is nonfunctional

32. Enzyme Specificity

33. Competitive Inhibition

34. Noncompetitive Inhibition

35. Inhibition of Enzyme Activity

36. Regulation of Enzyme Activity • To regulate metabolic pathways, the cell switches on/off the genes that encode specific enzymes • Allosteric regulation: protein’s function at one site is affected by binding of a regulatory molecule to a separate site (allosteric site) • Activator– stabilizes active site • Inhibitor– stabilizes inactive form • Cooperativity– one substrate triggers shape change in other active sites  increase catalytic activity

39. Feedback Inhibition • End product of a metabolic pathway shuts down pathway by binding to the allosteric site of an enzyme • Prevent wasting chemical resources, increase efficiency of cell

40. Feedback Inhibition