1. Energy Flow in the Life of a Cell

2. Figure: 05-00CO
Title:
Runners convert energy.
Caption:
The bodies of these runners are efficiently converting energy stored in fats and carbohydrates to the energy of movement and heat.

3. II. The nature of energy A. Energy undergoes transitions in forms
1. Potential energy—stored energy
2. Kinetic energy—energy of movement
3. Mechanical, chemical, electrical

4. II. The nature of energy B. Properties of energy
1. First law of thermodynamics
a. Total energy remains constant in a closed system
b. Energy cannot be created or destroyed

5. II. The nature of energy B. Properties of energy (cont.)
2. Second law of thermodynamics
a. In an isolated system, any change causes the quantity of concentrated, useful energy to decrease
b. Energy is converted from more useful to less useful forms

6. II. The nature of energy B. Properties of energy (cont.)
2. Second law of thermodynamics
c. Organization of matter and energy
1) Concentrated energy is more ordered (complex) chemically
2) Entropy—all processes in an isolated system result in an increase in randomness and disorder

7. Exergonic reaction reactants products Figure: 05-01UN01 Title:
An exergonic reaction.
Caption:
reactants
products

8. Endergonic reaction products reactants Figure: 05-01UN02 Title:
An endergonic reaction.
Caption:
products
reactants

9. III. Energy use in living things
A. Energy is stored in the chemical bonds of biological molecules

10. glucose oxygen carbon dioxide water
Figure: 05-01UN03
Title:
Burning sugar releases energy.
Caption:
oxygen
carbon
dioxide
water

11. III. Energy use in living things
C. Energy releasing chemical reactions are exergonic
1. High energy reactants  low energy products

12. water carbon dioxide glucose oxygen
Figure: 05-01UN03
Title:
Burning sugar releases energy.
Caption:
oxygen

13. III. Energy use in living things
D. Endergonic reactions require an energy input
1. Low energy reactants  high energy products
2. Do endergonic reactions create energy?
3. How can the product(s) of an endergonic reaction have more energy than the reactants without violating the Laws of Thermodynamics?

14. glucose oxygen carbon dioxide water
Figure: 05-01UN04
Title:
Photosynthesis requires energy.
Caption:
glucose
oxygen
carbon
dioxide
water

15. III. Energy use in living things
E. Chemical reactions and activation energy
Why does a match not spontaneously burn?

16. activation energy needed
Burning glucose (sugar): an exergonic reaction
activation energy needed
to ignite glucose
Figure: 05-02a
Title:
Energy relations in exergonic and endergonic reactions.
Caption:
(a) An exergonic (“downhill”) reaction, such as the burning of sugar, proceeds from high-energy reactants (here, glucose) to low-energy products (CO2 and H2O). The energy difference between the chemical bonds of the reactants and products is released as heat. To start the reaction, however, an initial input of energy, the activation energy, is required.

17. Photosynthesis: an endergonic reaction
(b)
Photosynthesis: an endergonic reaction
glucose
Figure: 05-02b
Title:
Energy relations in exergonic and endergonic reactions.
Caption:
(b) An endergonic (“uphill”) reaction, such as photosynthesis, proceeds from low-energy reactants (CO2 and H2O) to high-energy products (glucose) and therefore requires a large input of energy, in this case from sunlight.

18. III. Energy use in living things
F. Coupling of exergonic and endergonic reactions
1. Exergonic reaction provides energy to drive endergonic reactions
2. How is the energy that is released from an exergonic reaction harnessed and directed to drive its related endergonic reaction?

19. III. Energy use in living things
F. Coupling of exergonic and endergonic reactions (cont.)
3. Energy carrier molecules (energy taxis)
ATP and electron carrier molecules

20. ATP synthesis: Energy is stored in ATP
Figure: 05-02UN01
Title:
ATP synthesis.
Caption:
ATP
ADP
phosphate

21. ATP breakdown: Energy of ATP is released
Figure: 05-02UN02
Title:
ATP breakdown.
Caption:
ATP
ADP
phosphate

22. contracted muscle contracted muscle
Exergonic reaction:
Endergonic reaction:
contracted
muscle
relaxed
muscle
Coupled reaction:
Figure: 05-03
Title:
A coupled reaction.
Caption:
The exergonic reaction of ATP breakdown must precede the endergonic reaction of muscle movement.
relaxed
muscle
contracted
muscle

23. breakdown of ATP is used to power protein synthesis.
Energy released from
breakdown of glucose
is transferred to ATP.
Energy released from
breakdown of ATP is used
to power protein synthesis.
exergonic
(glucose
breakdown)
endergonic
(ATP synthesis)
exergonic
(ATP breakdown)
endergonic
(protein synthesis)
Figure: 05-04
Title:
Coupled reactions give off heat.
Caption:
The overall reaction is “downhill”: More energy is produced by the exergonic reaction than is needed to drive the endergonic reaction. The extra energy is released as heat.
overall exergonic
“downhill” reaction

24. exergonic (energized reaction carrier) (depleted endergonic carrier)
Figure: 05-05
Title:
Electron carriers.
Caption:
An electron-carrier molecule such as NAD+ picks up an electron generated by an exergonic reaction and holds it in a high-energy outer electron shell. The electron is then deposited, energy and all, with another molecule to drive an endergonic reaction, typically the synthesis of ATP.
overall exergonic
“downhill” reaction

25. Initial reactant Intermediates Final products PATHWAY 1 PATHWAY 2
Figure: 05-06
Title:
Simplified view of metabolic pathways;
Caption:
The original reactant molecule, A, undergoes a series of reactions. The product of each reaction serves as the reactant for the next reaction in the pathway or for a reaction in another pathway.
PATHWAY 2

26. IV. Chemical reactions in living organisms need to be catalyzed
A. Activation energy requirements for all the chemical reactions occurring in an organism are too high
B. Catalysts reduce activation energy requirements

27. activation energy without catalyst activation energy with catalyst
Figure: 05-07
Title:
Catalysts reduce activation energy.
Caption:

28. IV. Chemical reactions in living organisms need to be catalyzed
C. Enzymes catalyze reactions in living organisms
1. Bring reactant molecules close together
2. Make bonds easier to break

29. IV. Chemical reactions in living organisms need to be catalyzed
C. Enzymes catalyze reactions in living organisms (cont.)
3. Enzymes are very specific
a. Specificity is based on shape of enzyme and substrate
b. Lock and key analogy

30. IV. Chemical reactions in living organisms need to be catalyzed
C. Enzymes catalyze reactions in living organisms (cont.)
4. Most enzymes function as parts of complex, regulated biochemical pathways
5. Most enzymes are proteins
Mutation and loss of enzyme function

31. substrates enzyme substrates enzyme substrates enzyme
3 Substrates, bonded together,
leave enzyme; enzyme is
ready for new set of substrates.
active site
of enzyme
1 Substrates enter
active site in a
specific orientation.
2 Substrates and active site
change shape, promoting
reaction between substrates.
enzyme
substrates
active site
of enzyme
enzyme
1 Substrates enter
active site in a
specific orientation.
2 Substrates and active site
change shape, promoting
reaction between substrates.
substrates
active site
of enzyme
enzyme
1 Substrates enter
active site in a
specific orientation.
Figure: 05-08
Title:
The cycle of enzyme–substrate interactions.
Caption: