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Chapter 8 An Introduction To Metabolism. Metabolism u The totality of an organism’s chemical processes. u Concerned with managing the material and energy.

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Presentation on theme: "Chapter 8 An Introduction To Metabolism. Metabolism u The totality of an organism’s chemical processes. u Concerned with managing the material and energy."— Presentation transcript:

1 Chapter 8 An Introduction To Metabolism

2 Metabolism u The totality of an organism’s chemical processes. u Concerned with managing the material and energy resources of the cell.


4 Catabolic Pathways u Pathways that break down complex molecules into smaller ones, releasing energy. u Example: Respiration

5 Anabolic Pathways u Pathways that consume energy, building complex molecules from smaller ones. u Example: Photosynthesis

6 Energy u Ability to do work. u The ability to rearrange a collection of matter. u Forms of energy: u Kinetic u Potential u Activation


8 Kinetic Energy u Energy of action or motion.

9 Potential Energy u Stored energy or the capacity to do work.

10 Activation Energy u Energy needed to convert potential energy into kinetic energy. Potential Energy Activation Energy

11 Energy Transformation u Governed by the Laws of Thermodynamics.

12 1st Law of Thermodynamics u Energy can be transferred and transformed, but it cannot be created or destroyed. u Also known as the law of “Conservation of Energy”

13 2nd Law of Thermodynamics u Each energy transfer or transformation increases the entropy of the universe.

14 Entropy u Measure of disorder.

15 Summary u The quantity of energy in the universe is constant, but its quality is not.

16 Question? u How does Life go against Entropy? u By using energy from the environment or external sources (e.g. food, light).

17 Free Energy u The portion of a system's energy that can perform work.

18 Free Energy G = H - TS G = free energy of a system H = total energy of a system T = temperature in o K S = entropy of a system

19 Free Energy of a System u If the system has: u more free energy u it is less stable u It has greater work capacity

20 Spontaneous Process u If the system is unstable, it has a greater tendency to change spontaneously to a more stable state. u This change provides free energy for work.


22 Free Energy Changes

23 Chemical Reactions u Are the source of energy for living systems. u Are based on free energy changes.

24 Reaction Types u Exergonic: chemical reactions with a net release of free energy. u Endergonic: chemical reactions that absorb free energy from the surroundings.

25 Exergonic/Endergonic

26 Biological Examples u Exergonic - respiration u Endergonic - photosynthesis

27 Cell - Types of Work u Mechanical - muscle contractions u Transport - pumping across membranes u Chemical - making polymers

28 Cell Energy u Couples an exergonic process to drive an endergonic one. u ATP is used to couple the reactions together.


30 ATP u Adenosine Triphosphate u Made of: - Adenine (nitrogenous base) - Ribose (pentose sugar) - 3 phosphate groups


32 Adenine Ribose Phosphates

33 Key to ATP u Is in the three phosphate groups. u Negative charges repel each other and makes the phosphates unstable.

34 ATP u Works by energizing other molecules by transferring phosphate groups.


36 ATP vs Food u ATP: u Renewable energy resource. u Unstable bonds u Food: u Long term energy storage u Stable bonds

37 ATP Cycles u Energy released from ATP drives anabolic reactions. u Energy from catabolic reactions “recharges” ATP.

38 ATP Cycle

39 ATP in Cells u A cell's ATP content is recycled every minute. u Humans use close to their body weight in ATP daily. u No ATP production equals quick death.

40 Enzymes u Biological catalysts made of protein. u Cause the rate of a chemical reaction to increase.


42 Enzymes u Lower the activation energy for a chemical reaction to take place.


44 Enzyme Terms u Substrate - the material the enzyme works on. u Enzyme names: Ex. Sucrase - ase name of an enzyme 1st part tells what the substrate is. (Sucrose)

45 Enzyme Name u Some older known enzymes don't fit this naming pattern. u Examples: pepsin, trypsin

46 Active Site u The area of an enzyme that binds to the substrate. u Structure is designed to fit the molecular shape of the substrate. u Therefore, each enzyme is substrate specific.




50 Homework u Read chapter 8, 41 u Exam 2 – this week, no broadcast on Thursday u Chapter 8 – Fri. 10/10 u Chapter 41 – Mon. 10/20

51 Models of How Enzymes Work 1. Lock and Key model 2. Induced Fit model

52 Lock and Key Model u Substrate (key) fits to the active site (lock) which provides a microenvironment for the specific reaction.

53 Induced Fit Model u Substrate “almost” fits into the active site, causing a strain on the chemical bonds, allowing the reaction.

54 Substrate Active Site

55 Enzymes u Usually specific to one substrate. u Each chemical reaction in a cell requires its own enzyme.

56 Factors that Affect Enzymes u Environment u Cofactors u Coenzymes u Inhibitors u Allosteric Sites

57 Environment u Factors that change protein structure will affect an enzyme. u Examples: u pH shifts u temperature u salt concentrations

58 u Cofactors: non-organic helpers required for the proper function of enzymes. u Nonprotein ions or molecules u Ex. Fe, Zn, Cu u NADH u Coenzyme Q

59 u Coenzymes: organic helpers to enzymes. Ex. vitamins

60 Enzyme Inhibitors u Competitive - mimic the substrate and bind to the active site. u Noncompetitive - bind to some other part of the enzyme.


62 Allosteric Regulation u The control of an enzyme complex by the binding of a regulatory molecule. u Regulatory molecule may stimulate or inhibit the enzyme complex.

63 Allosteric Regulation

64 Control of Metabolism u Is necessary if life is to function. u Controlled by switching enzyme activity "off" or "on” or separating the enzymes in time or space.

65 Types of Control u Feedback Inhibition u Structural Order

66 Feedback Inhibition u When a metabolic pathway is switched off by its end- product. u End-product usually inhibits an enzyme earlier in the pathway.


68 Structural Order u Separation of enzymes and metabolic pathways in time or space by the cell's organization. u Example: enzymes of respiration


70 Summary u Recognize that Life must follow the Laws of Thermodynamics. u The role of ATP in cell energy. u How enzymes work.

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