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. An Introduction to Metabolism
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.

8. The living cell Bioluminescence
Is a miniature factory where thousands of reactions occur
Converts energy in many ways
Figure 8.1
Bioluminescence

9. Metabolism Is the totality of an organism’s chemical reactions
Arises from interactions between molecules
An organism’s metabolism transforms matter and energy, subject to the laws of thermodynamics

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

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

12. 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 converted from one form to another
Eg. chemical  mechanical  electrical

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

15. 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

16. An example of energy conversion
Figure 8.3 
First law of thermodynamics: Energy can be transferred or transformed but
Neither created nor destroyed. For
example, the chemical (potential) energy
in food will be converted to the kinetic
energy of the cheetah’s movement in (b).
(a)
Chemical
energy

17. 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

18. The Second Law of Thermodynamics
According to the second law of thermodynamics
Spontaneous changes that do not require outside energy increase the entropy, or disorder, of the universe
The Second Law of Thermodynamics
Figure 8.3 
Second law of thermodynamics: Every energy transfer or transformation increases
the disorder (entropy) of the universe. For example, disorder is added to the cheetah’s
surroundings in the form of heat and the small molecules that are the by-products
of metabolism.
(b)
Heat
co2
H2O +

20. Living systems Increase the entropy of the universe
Use energy to maintain order

21. A metabolic pathway has many steps
Metabolic Pathways
A metabolic pathway has many steps
That begin with a specific molecule and end with a product
That are each catalyzed by a specific enzyme
Enzyme 1
Enzyme 2
Enzyme 3 A B C D
Reaction 1
Reaction 2
Reaction 3
Starting molecule
Product

22. Types of Metabolic Pathways
Catabolic pathways
Break down complex molecules into simpler compounds
Release energy
Anabolic pathways
Build complicated molecules from simpler ones
Consume energy

24. Energy can be converted from one form to another
On the platform, a diver
has more potential energy.
Diving converts potential
energy to kinetic energy.
Climbing up converts kinetic
energy of muscle movement
to potential energy.
In the water, a diver has
less potential energy.
Figure 8.2

25. Free Energy
Free energy measures the portion of a system’s energy that can perform work when the temperature & pressure are uniform throughout the system. (like in cells)
The free-energy change of a reaction tells us whether the reaction occurs spontaneously
A living system’s free energy
Is energy that can do work under cellular conditions

29. Change in free energy, ∆G
The change in free energy, ∆G during a biological process
Is related directly to the enthalpy change (∆H) and the change in entropy
∆G = ∆H – T∆S
T = Absolute temp in Kelvin (K)

30. ∆G
The value of ∆ G for a reaction at any moment in time tells us two things.
The sign of ∆ G tells us in what direction the reaction has to shift to reach equilibrium.
The magnitude of ∆ G tells us how far the reaction is from equilibrium at that moment.

31. The system is at equilibrium
At maximum stability
The system is at equilibrium
Chemical reaction. In a cell, a sugar molecule is broken down into simpler molecules. .
Diffusion. Molecules in a drop of dye diffuse until they are randomly dispersed.
Gravitational motion. Objects
move spontaneously from a
higher altitude to a lower one.
More free energy (higher G)
Less stable
Greater work capacity
Less free energy (lower G)
More stable
Less work capacity
In a spontaneously change
The free energy of the system decreases (∆G <0)
The system becomes more stable
The released free energy can
be harnessed to do work
(a)
(b)
(c)
Figure 8.5 

32. Free Energy During a spontaneous change
Free energy decreases and the stability of a system increases
For a spontaneous reaction to occur:
Loss of enthalpy (Heat)
-or-
Loss of order (Gain in entropy)
-or both

33. 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

34. Exergonic and Endergonic Reactions in Metabolism
An exergonic reaction
Proceeds with a net release of free energy and is spontaneous
Figure 8.6
Reactants
Products
Energy
Progress of the reaction
Amount of
energy
released (∆G <0)
Free energy
(a) Exergonic reaction: energy released

35. (b) Endergonic reaction: energy required
Is one that absorbs free energy from its surroundings and is non-spontaneous
Figure 8.6
Energy
Products
Amount of
energy
released (∆G>0)
Reactants
Progress of the reaction
Free energy
(b) Endergonic reaction: energy required

40. Reactions in a closed system
Eventually reach equilibrium
Figure 8.7 A
(a) A closed hydroelectric system. Water flowing downhill turns a turbine that drives a generator providing electricity to a light bulb, but only until the system reaches equilibrium.
∆G < 0
∆G = 0

41. Reactions in an open system
Cells in our body
Experience a constant flow of materials in and out, preventing metabolic pathways from reaching equilibrium
Figure 8.7
(b) An open hydroelectric system. Flowing water keeps driving the generator because intake and outflow of water keep the system from reaching equilibrium.
∆G < 0

42. An analogy for cellular respiration
Figure 8.7
(c) A multi-step open hydroelectric system. Cellular respiration is analogous to this system: Glucose is broken down in a series of exergonic reactions that power the work of the cell. The product of each reaction becomes the reactant for the next, so no reaction reaches equilibrium.
∆G < 0

43. 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

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

45. 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

46. Phophorylation- The transferring of phosphoryl group from a donor to the recipient molecule
Phosphorylation is important in living cells since it is through this that energy-rich molecules (e.g. ATPs) are formed. For instance, a phosphoryl group (phosphate) is added to ADP, thus forming ATP, usually catalysed by phosphorylases and kinases.

47. ATP – Adenosine Tri-phosphate
ATP powers cellular work by coupling exergonic reactions to endergonic reactions
A cell does three main kinds of work
Mechanical
Transport
Chemical

48. 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)

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

50. 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)

53. 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

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

58. Enzyme Action: Catabolism

59. Enzyme Action: Anabolism

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

61. Cofactors
Cofactors are nonprotein enzyme helpers such as minerals (eg. Zn, Fe, Cu)
Coenzymes are organic cofactors (eg. vitamins)
Enzyme Inhibitors
Competitive inhibitor: binds to the active site of an enzyme, competes with substrate
Noncompetitive inhibitor: binds to another part of an enzyme  enzyme changes shape  active site is nonfunctional

62. Enzyme Specificity

63. Competitive Inhibition

64. Noncompetitive Inhibition

65. Inhibition of Enzyme Activity

66. 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

69. 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

70. Feedback Inhibition