Good

1. Lesson 15
BIOENERGETICS.
COMMON PATHWAYS OF CATABOLISM
1. What does bioenergetics study? Describe the first and second laws of thermodynamics.
2. Describe the first and second laws of thermodynamics.
3. What are enthalpy, entropy and free energy?
4. Give definition of metabolism? What is catabolism and anabolism? Describe stages of catabolism.
5. What are high energy compounds? Which high energy compounds do you know?
6. Which pathways of ATP synthesis occur in the organism?
7. Give the definition of oxidative phosphorylation.
8. Give the definition of substrate level phosphorylation.
9. What is the Electron Transport Chain (ETC)? Where in a cell is ETC located?
10. List the components of ETC. How are components of ETC arranged?
11. How is the energy released during transferring of electrons called? How is this energy used?
12. Describe Chemiosmotic Theory. What does the electrochemical potential (H+
gradient) consist of?
13. How many molecules of ATP are synthesized if the process of oxidation starts from NAD-dependent
dehydrogenase?
14. How many molecules of ATP are synthesized if the process of oxidation starts from FAD-dependent
dehydrogenase?
15. What is the P:O ratio?
16. What is the respiratory control or acceptor control?
17. What compounds can uncouple the electron transport from oxidative phosphorylation? Why does the
uncoupling provide generating of heat?
18. Name the inhibitors of oxidative phosphorylation.
19. Which processes are the final common pathway for catabolism of carbohydrates, lipids and proteins?
Where are they localized in a cell?
20. Describe pyruvate dehydrogenase complex. Give names for all enzymes and coenzymes
participating in this complex.
21. What do you know about Krebs cycle. What are its biological roles?
22. Which coenzymes are reduced during oxidation of substrates of Krebs cycle? How are they linked to
ETC?
23. How many ATP molecules yield one Krebs cycle?
24. How many ATP molecules are produced by oxidative phosphorylation in Krebs cycle? How many ATP
molecules are produced by substrate level phosphorylation in Krebs cycle?
25. Why is the Krebs cycle called amphibolic pathway in nature? Name intermediates of Krebs cycle may
be precursors for biosynthesis of other compounds?
26. Which enzyme in Krebs cycle is regulated? List the activators and inhibitors of this enzyme.
27. Describe glycerol phosphate and malate-aspartate shuttles mechanism.
LITERATURE:
1) Biochemistry. / Denise R. Ferrier. 6th ed. - 2011. - p. 69-82, 109-116
2) Biochemistry with exercises and tasks: / A. I. Glukhov, V. V. Garin. 2020. - p.91-108
3) Lectures 7, 8.

2. INTRODUCTION TO METABOLISM
Bioenergetics of the cell is the study of how organisms manage their energy resources
Energy is the capacity to perform work.
Potential Energy is stored energy. Examples: chemical energy.
Kinetic Energy is energy due to motion. Examples: the flow of electrons (electricity)
Thermodynamics is the study of energy transformations. Living systems are subject to
the laws of thermodynamics just like cars and furnaces.
1st
Law of Thermodynamics (Principle of Conservation of Energy): Energy can
neither be created nor destroyed, only transformed from one type to another.
2nd
Law of Thermodynamics: Spontaneous changes that do not require outside energy
increase the entropy, or disorder, of the universe.
The direction of a chemical reaction is determined by following equation:
∆G = ∆H – T∆S
Free energy (G) is the portion of system energy that can do work.
Enthalpy (H) is a measure of the change in heat content of the reactants, compared to products.
Entropy (S) represents a change in the randomness or disorder of reactants and products.
Temperature (T) is measured in Kelvins.
Metabolism is the sum of all the chemical processes occurring in an organism at one time
There are two types of metabolic pathways:
• Catabolic pathways:
 Break down complex molecules into simpler compounds
 Release energy
Ex. Hydrolysis, Cellular respiration
• Anabolic pathways:
 Build complicated molecules from simpler ones
 Consume energy
Ex. Protein synthesis.

3. The three stages of catabolism
At the first stage biopolymers (supplied in food ) convert to a monomeric form suitable
for energy extraction. This is accomplished by hydrolysis in the intestine. The energetic value
of this stage is about 1% of the energy is released, and it is dissipated as heat.
At the second stage, a large number of initial substrates become reduced to two only.
This stage is characterized by partial (to 20%) release, under anaerobic (oxygen-free)
conditions, of the energy contained in the initial substrates. Part of this energy accumulates in
ATP. The conversion of monomers proceeds in the cytoplasm.
At the third stage the two metabolites are oxidized to CO2 in the final common
oxidative pathway. In this process, NADH and FADH2 are generated. These reducing
equivalents (NADH and FADH2) enter into the electron transport chain (ETC), where energy is
released. About 80% of the total chemical bond energy of compounds involved is released at
this stage. This energy, generated in the ATP. This stage is in the mitochondria.

4. During biological oxidations, the reacting chemical systems move from a higher energy
level to a lower one and therefore there is liberation of energy. The energy released as heat is
converted to chemical energy by formation of high energy compound.
Compounds which liberate more than 7.0 Cal/mol are called high-energy compounds.
Standard free energy of hydrolysis of some important compounds
High energy bond in compounds is usually indicated by a squiggle bond (~).
ATP is the universal currency of energy within the living cells. The
hydrolysis of ATP to ADP releases –30.5 kJ/mol or –7.3 Cal/mol

5. There are two pathways of ATP synthesis:
1. Oxidative phosphorylation
is synthesizes ATP from ADP and H3PO4 , utilizing the energy of the proton
gradient (H+
gradient) generated by the Electron Transport chain (ETC)
I
FMN,
Fe-S
III
b, c1,
Fe-S
II
Fe-S
FADH2
IV
a,a3
V
F0
F1
inner
membrane
Intermembrane space
Matrix
CoQ
C
NADH
2H+ 2H+ 2H+
1/2O2
H2O
6 H+
+ + + + +
- - - -
3 ADP + 3H3PO4 →3 ATP
NADH→ 3 ATP
FADH2→ 2 ATP
S
S
2. Substrate level phosphorylation
is the process of energy transportation from a high-energy compound to ADP
with forming ATP without helping ETC

6. COMMON PATHWAYS OF CATABOLISM:
OXIDATIVE DECARBOXYLATION OF PYRUVATE
TRICARBOXYLIC ACID CYCLE

7. There are special shuttle systems carry reducing equivalents from cytosolic NADH into
the mitochondria
Glycerol phosphate shuttle
2 ATP
Malate-aspartate shuttle
3 ATP