1. An Introduction to Metabolism
A.P. Biology
Chapter 8

2. Why do you eat? What is the purpose of a food chain?
Answer: Energy and Organic Building Blocks

3. Bioenergetics
Bioenergetics- how energy behaves and changes in living systems (food chains).
Metabolism = Anabolism (require energy to make new bonds) + Catabolism (release energy from bonds)

4. Energy-The Stuff of Life!
Energy – the capacity to do work.
Two States of Energy:
Kinetic Energy- energy of motion.
Potential Energy- stored energy.
Potential  Kinetic  Potential

5. Forms of energy? Chemical Mechanical Electrical Light HEAT Nuclear
Biology – potential chemical and kinetic chemical; light; heat (from chemical bonds)

6. Some organisms Convert chemical energy to light, as in bioluminescence
Figure 8.1

7. Measuring Energy in Biology
In terms of heat changes (thermodynamics).
Unit of heat in biology – calorie.
1.0 calorie = amount of heat req’d to raise 1.0g of H20, 1° C.
In biology, 1.0 kilocalorie (kcal) = 1,000.0 calories (cal)
1,000 cal = 1.0 kcal. = 1.0 Calorie

8. 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

9. Photosynthesis
Conversion of unusable light energy into usable chemical energy.
C6H12O6

10. Redox Reactions

11. Photosynthesis Light Stores 686 kcal/mol 6 CO2 + 12 H2O  6 O2 + 6 H2O
C6H12O6
Stores 686 kcal/mol

12. Photosynthesis is a Redox Reaction
6 CO H2O  6 O2 + 6 H2O
C6H12O6 H

13. Cellular Respiration C6H12O6 + 6 O2  6 CO2 + 6 H2O + ENERGY (ATP)
686 kcal/mole glucose

14. Cellular Respiration is a Redox Reaction
C6H12O6 + 6 O2  6 CO2 + 6 H2O ENERGY (ATP)
686 kcal/mole glucose H

15. First Law of Thermodynamics
Energy cannot be created nor destroyed, but it can be converted from one form to another.
Ex. Food chains

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. First Law of Thermodynamics
Producers (Light Energy  Potential Chemical)
1st Order Consumer or Herbivore (Potential Chemical Potential, Kinetic Chemical)
2nd Order Consumer or Carnivore (Potential Chemical Potential, Kinetic Chemical)
HEAT
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
Figure 8.3  (b
Heat
co2
H2O +

19. Biological Order and Disorder
Living systems
Increase the entropy of the universe
Use energy to maintain order
50µm
Figure 8.4

20. 2nd Law of Thermodynamics
As energy is transformed from one state to another, some of the energy is lost as heat (random molecular motion) and the ability to do work decreases.
Disorder (Entropy) in the universe is increasing.
Order  Disorder

21. Free-Energy Change, G A living system’s free energy
Is energy that can do work under cellular conditions

22. 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 spontaneous 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 
At maximum stability
The system is at equilibrium

23. Chemical Bonds have Potential Energy
When bonds are broken, some of the energy is lost as heat and is not available to do work (form new chemical bonds).
Free Energy (G) – the amt. of energy in a bond available to do work.
In a molecule, the amt. of Free Energy (G) = the amt. of energy in chemical bond (Enthalpy, H) – the energy lost as disorder (Entropy, S). G = H - TS

24. Free Energy of Chemical Rxns.
ΔG = difference in bond energies between reactants and products of a chemical reaction.
Δ G = ΔH – TΔS
If ΔG is negative (products contain less energy than reactants) = Exergonic Reactions. Ex. Cellular Respiration
If ΔG is positive (products contain more energy than reactants) = Endergonic Reactions. Ex. Photosynthesis

25. HEAT Free Energy  G Cellular Respiration Rxn Time C6H12O6 + O2
CO2 + H2O
Cellular Respiration
Rxn Time

26. Light Energy Supplied Free Energy  G Photosynthesis Rxn Time
C6H12O6 + O2
Light Energy Supplied
Free Energy  G
Photosynthesis
CO2 + H2O
Rxn Time

27. 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

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

29. Equilibrium and Metabolism
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

30. 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 equlibrium.
∆G < 0

31. An analogy for cellular respiration
Figure 8.7
(c) A multistep open hydroelectric system. Cellular respiration is analogous to this system: Glucoce is brocken 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

32. Concept 8.3: ATP powers cellular work by coupling exergonic reactions to endergonic reactions
A cell does three main kinds of work:
Mechanical
Transport
Chemical
Energy coupling
Is a key feature in the way cells manage their energy resources to do this work

33. The Structure and Hydrolysis of ATP
ATP (adenosine triphosphate)
Is the cell’s energy shuttle
Provides energy for cellular functions
Figure 8.8 O
CH2 H OH N C HC
NH2
Adenine
Ribose
Phosphate groups - CH

34. Adenosine triphosphate (ATP) Adenosine diphosphate (ADP)
Energy is released from ATP
When the terminal phosphate bond is broken
Figure 8.9 P
Adenosine triphosphate (ATP)
H2O +
Energy
Inorganic phosphate
Adenosine diphosphate (ADP)
P i

35. Can be coupled to other reactions
ATP hydrolysis:
Can be coupled to other reactions
Endergonic reaction: ∆G is positive, reaction
is not spontaneous
∆G = +3.4 kcal/mol
Glu
∆G = kcal/mol
ATP
H2O +
NH3
ADP
NH2
Glutamic
acid
Ammonia
Glutamine
Exergonic reaction: ∆ G is negative, reaction
is spontaneous P
Coupled reactions: Overall ∆G is negative;
together, reactions are spontaneous
∆G = –3.9 kcal/mol
Figure 8.10

36. How ATP Performs Work ATP drives endergonic reactions:
By phosphorylation, transferring a phosphate to other molecules

37. The three types of cellular work Are powered by the hydrolysis of ATP
(c) Chemical work: ATP phosphorylates key reactants P
Membrane
protein
Motor protein
P i
Protein moved
(a) Mechanical work: ATP phosphorylates motor proteins
ATP
(b) Transport work: ATP phosphorylates transport proteins
Solute
transported
Glu
NH3
NH2 +
Reactants: Glutamic acid
and ammonia
Product (glutamine)
made
ADP
Figure 8.11

38. The Regeneration of ATP
Catabolic pathways
Drive the regeneration of ATP from ADP and phosphate
ATP synthesis from
ADP + P i requires energy
ATP
ADP + P i
Energy for cellular work
(endergonic, energy-
consuming processes)
Energy from catabolism
(exergonic, energy yielding
processes)
ATP hydrolysis to
ADP + P i yields energy
Figure 8.12