Unit 1 Bioenergetics.pdf biochemistry b pharm 1st. yr
1. PT 214 BIOCHEMISTRY (THEORY)
UNIT I: BIOENERGETICS
Presented By:
Mr. Arnab Seth
Asst. Prof., Dept. of Pharm. Chem.
Bharat Technology
ARS, Asst. Prof., Dept. of Pharm. Chem., BT
2. BIOENERGETICS
• Bioenergetics or biochemical thermodynamics deals with the study of energy
changes (transfer and utilization) in biochemical reactions.
• The reactions are broadly classified as exergonic (energy releasing) and endergonic
(energy consuming).
• Biologic systems are essentially isothermic and use chemical energy to power living
processes.
ARS, Asst. Prof., Dept. of Pharm. Chem., BT
3. FREE ENERGY
• The energy actually available to do work (utilizable) is known as free energy.
• Gibbs change in free energy (ΔG) is that portion of the total energy change in a
system that is available for doing work— that is, the useful energy, also known as the
chemical potential.
• Enthalpy (ΔH) is a measure of the change in heat content of the reactants, compared
to products.
• Entropy (ΔS) represents a change in the randomness or disorder of reactants and
products.
ARS, Asst. Prof., Dept. of Pharm. Chem., BT
4. THE RELATION BETWEEN THE CHANGES OF
FREE ENERGY (ΔG), ENTHALPY (ΔH) AND
ENTROPY (ΔS)
• T represents the absolute temperature in Kelvin (K = 273 + °C).
• The term standard free energy represented by ΔG° (note the superscript°) is often
used.
• It indicates the free energy change when the reactants or products are at a
concentration of 1 mol/l at pH 7.0.
ARS, Asst. Prof., Dept. of Pharm. Chem., BT
5. NEGATIVE AND POSITIVE ΔG
ARS, Asst. Prof., Dept. of Pharm. Chem., BT
• If free energy change (ΔG) is represented by a negative sign, there is a loss of free
energy.
• The reaction is said to be exergonic,and proceeds spontaneously.
• On the other hand, a positive ΔG indicates that energy must be supplied to the
reactants.
• The reaction cannot proceed spontaneously and is endergonic in character.
6. EXAMPLE OF EXERGONIC AND
ENDERGONIC REACTIONS
• The hydrolysis of ATP is a classical example of exergonic reaction
• The reversal of the reaction (ADP + Pi → ATP) is endergonic and occurs only when
there is a supply of energy of at least 7.3 Cal/mol (ΔG° is positive).
ARS, Asst. Prof., Dept. of Pharm. Chem., BT
7. ΔG AT A CONSTANT
TEMPERATURE AND PRESSURE
• At a constant temperature and pressure,
ΔG is dependent on the actual
concentration of reactants and products.
• For the conversion of reactant A to
product B (A → B), the following
mathematical relation can be derived
ARS, Asst. Prof., Dept. of Pharm. Chem., BT
8. ΔG° IS RELATED TO EQUILIBRIUM
CONSTANT (Keq)
• When a reaction is at equilibrium (eq), the free energy change is zero.
• Hence ΔG° = −RT In Keq.
ARS, Asst. Prof., Dept. of Pharm. Chem., BT
9. REDOX POTENTIAL (E0)
• The oxidation-reduction potential or, simply, redox potential, is a quantitative
measure of the tendency of a redox pair to lose or gain electrons.
• The redox pairs are assigned specific standard redox potential (E0 volts) at pH 7.0
and 25°C.
• More negative redox potential → lose electrons.
• More positive redox potential → accept electrons.
ARS, Asst. Prof., Dept. of Pharm. Chem., BT
10. STANDARD REDOX
POTENTIAL (E0) OF
SOME OXIDATION-
REDUCTION
SYSTEMS
ARS, Asst. Prof., Dept. of Pharm. Chem., BT
Redox Pair E0 Volts
Succinate / α-ketoglutarate - 0.67
2H+/ H2 -0.42
NAD+/NADH -0.32
NADP+/NADPH -0.32
FMN/FMNH2 (enzyme bound) -0.30
Lipolate (ox/red) -0.29
Pyruvate/ Lactate -0.19
Fumarate / Succinate +0.03
Cytochrome b (Fe3+ / Fe2+) +0.07
Coenzyme Q (ox/red) +0.10
Cytochrome c1 (Fe3+ / Fe2+) +0.23
Cytochrome c (Fe3+ / Fe2+) +0.25
Cytochrome a (Fe3+ / Fe2+) +0.29
½ O2 / H2O +0.82
11. HIGH-ENERGY COMPOUNDS
• Certain compounds are encountered in the biological system which, on hydrolysis,
yield energy.
• The term high-energy compounds or energy rich compounds is usually applied to
substances which possess sufficient free energy to liberate at least 7 Cal/mol at pH
7.0 .
• Certain other compounds which liberate less than 7.0 Cal/mol (lower than ATP
hydrolysis to ADP + Pi) are referred to as low-energy compounds.
ARS, Asst. Prof., Dept. of Pharm. Chem., BT
12. STANDARD FREE ENERGY OF HYDROLYSIS
OF SOME IMPORTANT COMPOUNDS
High energy phosphates
Compounds ΔG° (Cal/mol)
Phosphoenol pyruvate -14.8
Carbamoyl phosphate -12.3
Cyclic AMP -12.0
1,3-Bisphosphoglycerate -11.8
Phosphocreatine -10.3
Acetyl phosphate -10.3
S-Adenosylmetheonine -10.0
Pyrophosphate -8.0
Acetyl CoA -7.7
ATP → ADP + Pi -7.3
Low-energy phosphates
Compounds ΔG° (Cal/mol)
ADP → AMP + Pi -6.6
Glucose-1-phosphate -5.0
Fructose-6-phosphate -3.8
Glucose-6-phosphate -3.3
Glycerol-3-phosphate -2.2
ARS, Asst. Prof., Dept. of Pharm. Chem., BT
13. CLASSIFICATION OF HIGH-ENERGY
COMPOUNDS
High energy
compounds
Pyrophosphate ATP, pyrophosphate
Acyl phosphate
1,3-Bisphosphoglycerate, carbamoyl
phosphate, acetyl phosphate
Enol phosphate Phosphoenol pyruvate
Thiol esters Acetyl CoA, Acyl CoA
Guanidio phosphate Phosphocreatine, phosphoarginine
ARS, Asst. Prof., Dept. of Pharm. Chem., BT
15. ROLE OF ATP/ADP
CYCLE IN TRANSFER
OF HIGH-ENERGY
PHOSPHATE
ARS, Asst. Prof., Dept. of Pharm. Chem., BT
16. ATP
Energy source of
biochemical
reactions
synthesis of Phosphocreatine from creatine
synthesis of FA from acetyl CoA
synthesis of peptides and proteins from amino acids
formation of glucose from pyruvic acid
synthesis of glutamine
important source of energy for
Muscle contraction
transmission of nerve impulses
Transport of nutrients across cell
membranes,
motility of spermatozoa
formation of active
methionine
donates Phosphate for a variety of phosphotransferase reactions
formation of chondroitin SO4
ARS, Asst. Prof., Dept. of Pharm. Chem., BT
BIOLOGICAL
SIGNIFICANCE OF ATP
17. THE FORMATION AND HYDROLYSIS OF
CYCLIC AMP
ARS, Asst. Prof., Dept. of Pharm. Chem., BT
