bio-energitics

1
BIO-ENERGITICS

• M.Prasad Naidu
• MSc Medical Biochemistry,
• Ph.D.Research Scholar

2
Bio-energitics

• Bio-energitics is the study of energy
  changes release or utilization in
  biochemical reactions.
• Reactions where energy is released are
  called exergonic reactions.
• Reactions where energy is utilized are
  called endergonic reactions.

3
BIO-ENERGITICS

• Free energy G
• Gibb's change in free energy G
• negative
• positive
• zero
• Standard free energy Go
• Enthalpy H
• Entropy S

4
Bio-energitics

• Free energy G denotes the fraction total
  energy in the system available to do the work .
  
• Gibbs change in free energy G It is the
  portion of free energy that is useful to do the
  work.
• Standard free energy change G0 is the
  free energy change under standard conditions pH
  7 and 1M\ L concentration

5
Bio-Energitics

• Gibbs Change in free energy G
• predicts whether a reaction is favorable or
  not
• and the energy available to do work.
• 1. exergonic reactions
  negative
• 2.endergonic reactions
  positive
• 3.equilibrium reactions
  zero

6
BIO-ENERGITICS
Enthalpy H is the measure of the change in
the heat content of the system i.e. energy
released or absorbed. Entropy S It is the
fraction of enthalpy that is not available to do
the work. it denotes the randomness of the
products and reactants.

7
BIO- ENERGITICS

• A biochemical reaction depends on
• the change in free energy , Enthalpy ,
• and Entropy.
• G H - T S
• T absolute temperature in
  
• 
  Kelvin

8
ATP

• ATP is the energy currency of the cell
• ATP on hydrolysis yields -7.3 Kcal
• 
  
  ATP
  ADP Pi - 7.3 Kcal
• ATP is utilized for Active transport
• Nerve
  conduction
• Muscle
  contraction
• synthetic
  reactions

9
High energy phosphates

• 1.Pyro-phosphates -------------- ATP
• 2.Acyl phosphates -------------- 1,3-BPG
• 3.Enol phosphates -------------- PEP
• 4.phosphoguanides ------------- creatine P
• 5.Thio - esters ------------- Acyl-co
  A
• the high energy bond in these compounds is called
  as Acid anhydride bond

10
High energy compounds

• phopho enol pyruvate -14.8Kcal
• phospho creatine
• 1,3-BPG
• SAM
• ATP - 7.3Kcal
• ADP
• G-1-P
• F-6-P
• G-6-P -3.3Kcal

11
Redox pairs

• The electrons flow uni directionally from one
  carrier to the other in ETC.
• The carriers are reduced when they accept the
  electrons and get oxidized when they donate to
  the other carrier.
• the reduced and oxidized forms of the same
  carrier are referred as redox pairs.
• Redox potential is the tendency of the redox pair
  to donate or accept electrons.
• electrons always flow from negative to positive
  redox potential.

12
Redox pairs

• REDOX PAIRS REDOX POTENTIAL
• NADH\NAD -0.32
• FADH\FAD -0.12
• H2O\O2 0.82
• The ETC is arranged in the increasing
• order of their redox potentials.

13
Enzymes of biological oxidation

• All the enzymes of biological oxidation
• belongs to the major class of
• oxido-reductases.
• They are classified as follows
• 1.Oxidases
• 2.Oxygenases
• 3.Hydroperoxidases
• 4.dehydrogenases

14
Enzymes in biological oxidation

• Class Oxido reductases
• Oxidases Eg Cytochrome oxidase
• Oxygenases
• Mono-oxygenases Eg Cyt P450
• Dioxygenases Eg Tryptophan dioxygenases
• Hydroperoxidases
• Peroxidases Eg Glutathione peroxidase
• Catalases
• Dehydrogenases
• Aerobic Eg Xanthine oxidase
• Anaerobic
• NAD linked
• FAD linked
• FMN linked

15
Enzymes

• 1.Oxidases these enzymes catalyze
• the removal of hydrogen from the substrates.
• Oxygen acts as acceptor of hydrogen
  forming water.
• E.g. cytochrome -oxidase ,MAO
• A H2 1\2 O2 ---------- A
  H2O

16
Enzymes

• 2.Oxygenases
• Mono-oxygenases mixed function oxidase
• incorporates one oxygen atom into the
  
• substrate other is reduced to water.
• E.g. cyt-P450 ,tyrosine hydroxylase etc.
• A-H O2 BH2 AOH
  H2O B
• 2. di-oxygenases incorporate both oxygen atoms
  into the substrate.
• E.g. Tryptophan dioxygenase
• A H O2
  AOOH
• 
  

17
Enzymes

• 3. Hydroperoxidases act on H2O2.
• 1. peroxidase glutathione peroxidase
• AH2 H2O2 ---------2H2O A
• 2.catalase
• 2H2O2 ----------------2H2O O2

18
ENZYMES

• 4.Dehydrogenases
• Catalyze the removal of hydrogen from the
  substrate. Based on the type of H2 acceptor
  they are
• classified as follows
• 1. aerobic dehydrogenases oxygen is the
  acceptor of hydrogen.
• 2. anaerobic dehydrogenases coenzymes act
  as
• acceptors of hydrogen
• NAD linked dehydrogenases
• NADP linked dehydrogenases
• FAD- linked dehydrogenases

19
Enzymes

• Aerobic dehydrogenases
• These are flavoproteins and the product formed
  is mostly hydrogen peroxide
• AH2 O2 -------------A H2O2
• E.g. xanthine oxidase, glucose oxidase etc

20
Enzymes

• Anaerobic dehydrogenases hydrogen acceptor s are
  co-enzymes. When the substrate is oxidized the
  co-enzyme is reduced
• AH2 B ----------------A BH2

21
Electron transport chain

• Transport of electrons from reduced
• substrates to O2 is called as ETC.
• Site Inner mitochondrial membrane
• Components
• 1.Nicotinamide nucleotides NADH H /
  NAD
• 2.Flavo-proteins FADH2 / FAD.
• 3.Ubiquinone CoQ.
• 4. Cytochromes b, c1, c, a, a3.

22
ETC
ETC components are arranged in four
complexes in the increasing order of
their redox potentials from -4.2 for (NADH
H) to 0.82 for O2. Complex I NADH
H----- CoQ reductase. II
Succinate ----- CoQ reductase.
III Co-Q ------- Cyt C reductase.
IV Cytochrome oxidase.
23
ETC
24
ATPsynthase v
25

• ATP synthase Complex 5
• Integral protein in the inner mitochondrial
  membrane.
• It has two units F0 F1.
• F0 acts as a protein channel.
• F1 has ATP synthase activity.

26
(No Transcript)
27
Components of ETC

• 1.Nicotinamide nucleotides
• NADH H and NAD
• 2. flavo-proteins FADH2 and FAD

28
Components of ETC

• 3. Co- Q ubiquinone

29
Components of ETC

• 4. cytochromes

30
ETC

• PO ratio is the number of P atoms utilized
• To synthesize ATP for one atom of O2
• oxidized
• PO ratio for NADH H is 3
• three sites of ATP synthesis
• PO ratio for FADH2 is 2
• two sites of ATP synthesis

31
Theories of oxidative phosphorylation

• 1. Chemical coupling
• Generation of ATP at substrate level.
• 2. Conformational coupling
• Conformational changes in the molecules in
  
• mitochondrial membrane leads to ATP
• generation.
• 3. Chemi -osmotic theory The proton gradient
  generated during electron
• transfer is utilized for ATP synthesis.

32
(No Transcript)
33
Inhibitors of ETC

• Site specific
• 1. NADH H to CoQ
• 1.Rotenone
• 2.piericidin
• 3.
  amylobarbital
• 2. Cyt b to Cyt c1
• 1. Antimycin
  
• 2. BAL.
• 3. Cyt a3 to O2
• 1. HCN
• 2. H2S
• 3. CO.

34
Inhibitors of oxidative phosphorylation

• Uncouplers 2,3 dinitrophenol,
• 2,3
  dinitrocresol
• Physiological uncouplers
• Large doses of 1. Unconjugated bilirubin,
• 2.
  Thyroxine
• 3.
  Aspirin
• 
  4. Long chain fatty acids.
• 1. Oligomycin Blocks ATP synthase
  activity.
• 2.Atractyloside Block the proton
  flow into the
• 
  mitochondrial matrix.

35
(No Transcript)
36
(No Transcript)
37
(No Transcript)
38
(No Transcript)