Biochemistry

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Biochemistry 8th lecture Content
Introduction in metabolism. Stages of metabolism
. Common metabolic pathways. Specific role of
ATP. Biological oxidation. Mitochondria and their
role in the cell energetics. Respiratory chain.
Oxidative phosphorylation.
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Introduction in metabolism and common
metabolic pathways Metabolism is the sum of all
enzymatic reactions proceeding in the organism
. The biological role of metabolism is 1.
Transform energy in form of transformed another
chemical bonds 2. Transform exogenous products to
the building blocks 3. Synthesise specific
biomolecules for appropriate organism and
polymers from building blocks 4 .Synthesise and
cleave biomolecules with specific
functions Metabolism consists of three separate
processes 1. Catabolism 2. Anabolism 3.
Amphibolic metabolic processes In the
multicellular organism catabolic process consists
of three stages 1. Digestion 2. Cytoplasmic
stage of breakdown 3. Mitochondrial stage of
breakdown - common metabolic pathways
a) oxidative decarboxylation of pyruvate
b) transformation of propionyl-coenzyme A and
its breakdown c) tricarboxylic acid
cycle (citric acid cycle, Krebs cycle)
d) respiratory chain
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Different compounds NADH2 FADH2 Organic
phosphates NTP,KP Thio-anhydrides RS CO-...
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Energetic value of phosphate bond may
be different
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Specific role of ATP in
metabolism (Energy
currency of the cell) 1) There are several
significant biochemical reactions which may
proceed exclusively using energy of ATP,
but not other energetic sources 2) ATP is the
most universal energy source 3) Among the
phosphorylated compounds ATP is in the
intermediate position Examples
Phosphoenolpyruvate 14,8 kcal/mole,
62,2 kJ/mole 1,3-
diphosphoglyceate 11,8
49,6 Kreatinphosphate
10,3 43,3
ATP
7,3 30,7
Glucose - 1- phosphate 5,0
21,0
Glycerol- 1- phosphate 2,2
9,2 Therefore ATP allows to realise
thermodynamically unfavourable reactions into
possible Glucose phosphate 13,8 kJ/mole
glucose -6- phosphate Glucose ATP(30,7- 13,8)
glucose -6- phosphate ADP 16,9 kJ/mole
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Adenosine triphosphate biosynthesis and using
of it in the cell

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Cytoplasmic Na/K exchange adenosine
triphosphatase, potassium pump, Na, K pump,
ATP phospohydrolase (Na/K exchange
) E.C.3.6.3.9. Enzyme was discovered by J.C.Skou
in 1957 (BBA,v.23,394-401)
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Characteristics of stages of
catabolism 1.Digestion hydrolytic process,
where the specificity of food is eliminated,
depolymerisation of polymers and definite
unification of energoplastic material
Proteins gt 1000 20
amino acids Nucleic acids gt 1000
4 bases,pentose, phosphate
Lipids gt 100 glycerol
20 fatty acids Sugars
gt 50 5 hexoses, 5 pentoses 2.
Cytoplasmic stage further unification of
energoplastic material. From the carbon
skeletons is formed 1)pyruvate,
2)acetylcoenzyme A , 3) 2- oxoglutarate
4)fumarate, 5)succinylcoenzyme A, 6)
oxaloacetae 3. Mitochondria the final
depersonification of carbon skeletons, complete
their breakdown, resulting in the
formation of carbon dioxide and reduced
coenzymes NADH2 and FADH2. Being oxidised in the
respiratory chain they give water, but the
energy of oxidation is transformed into
energy of macroergic bond - ATP. By oxidation of
the one mole of NADH2 may be formed 3 moles of
ATP, but
FADH2 2 Note
according to the newest data two moles of NADH2
gives 5 moles of ATP

FADH2 3
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Pyruvate oxidative decarboxylation
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Pyruvate dehydrogenase complex

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Citric acid cycle, Krebs cycle,
tricarboxylic acid cycle
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The Biological significance of citric acid
cycle
1. Citric cycle is integrated
with the oxidative phosphorylation
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2.Amphibolic character of citric acid cycle 3.May
be regulated 4.Final oxidation of carbon
skeletons of former sugars, lipids, amino
acids
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