Definition Metabolism (from Greek: "metabol", "change" or
Greek: metabolismos, "outthrow") is the set of chemical reactions
that happen in the cells of living organisms to sustain life.Greek
chemical reactionsorganisms These processes allow organisms to grow
and reproduce, maintain their structures, and respond to their
environments. Metabolism is usually divided into two categories.
Catabolism breaks down organic matter, for example to harvest
energy in cellular respiration.Catabolismcellular respiration
Anabolism uses energy to construct components of cells such as
proteins and nucleic acids. Anabolismproteinsnucleic acids
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Chemical Reaction The chemical reactions of metabolism are
organized into metabolic pathways, in which one chemical is
transformed through a series of steps into another chemical, by a
sequence of enzymes.metabolic pathwaysenzymes Enzymes are crucial
to metabolism because they allow organisms to drive desirable
reactions that require energy and will not occur by themselves, by
coupling them to spontaneous reactions that release
energy.energycouplingspontaneous reactions As enzymes act as
catalysts they allow these reactions to proceed quickly and
efficiently.catalysts Enzymes also allow the regulation of
metabolic pathways in response to changes in the cell's environment
or signals from other cells.regulationcell'ssignals
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Selective reaction The metabolism of an organism determines
which substances it will find nutritious and which it will find
poisonous. nutritiouspoisonous For example, some prokaryotes use
hydrogen sulfide as a nutrient, yet this gas is poisonous to
animals.prokaryotes The speed of metabolism, the metabolic rate,
influences how much food an organism will require, and also affects
how it is able to obtain that food.metabolic rate
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CARBOHYDRATE DIGESTION AMYLUM digestion by amylase enzyme
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Disaccharides digestion
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Glucose is the most important carbohydrate Glucose is the major
metabolic fuel of mammals, except ruminants Monosaccharide from
diet : - Glucose - Glucose - Fructose - Fructose - Galactose -
Galactose Fructose and Galactose glucose at the liver
GLYCOLISIS Glycolisis oxidation of glucose energy It can
function either aerobically or anaerobically pyruvate lactate
pyruvate lactate Occurs in the cytosol of all cell AEROBICALLY
GLYCOLYSIS : Pyruvate Mitochondria oxidized to Asetil CoA Krebs
Cycle Pyruvate Mitochondria oxidized to Asetil CoA Krebs Cycle CO2
+ H2O + ATP CO2 + H2O + ATP
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Glycolisis
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Most of the reaction of glycolysis are reversible, except of
three reaction : 1. Glucose Glucose-6-phosphate, catalyzed by
Hexokinase / Glucokinase 1. Glucose Glucose-6-phosphate, catalyzed
by Hexokinase / Glucokinase Hexokinase : - Inhibited allosterically
by its product glucose-6-p - Inhibited allosterically by its
product glucose-6-p - Has a high affinity for its substrate glucose
- Has a high affinity for its substrate glucose - available at all
cell, except liver and islet cell - available at all cell, except
liver and islet cell
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Glucokinase : - available at liver and islet cell - available
at liver and islet cell - in the liver to remove glucose from the
blood after meal - in the liver to remove glucose from the blood
after meal 2. Fructose-6-P Fructose-1,6-biP 2. Fructose-6-P
Fructose-1,6-biP - catalyzed by Phosphofructokinase enzyme -
catalyzed by Phosphofructokinase enzyme - Irreversible -
Irreversible - Rate limiting enzyme in glycolysis - Rate limiting
enzyme in glycolysis 3. Phosphoenolpyruvate Enol Pyruvate 3.
Phosphoenolpyruvate Enol Pyruvate - Catalyzed by Pyruvate kinase
enzyme - Catalyzed by Pyruvate kinase enzyme Oxidation of 1 mol
glucose 8 mol ATP and 2 mol Pyruvate
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ANAEROBICALLY GLYCOLYSIS : - The reoxidation of NADH through
the respiratory chain to oxygen is prevented - The reoxidation of
NADH through the respiratory chain to oxygen is prevented -
Pyruvate is reduced by the NADH to lactate, by Lactate
dehidrogenase enzyme - Pyruvate is reduced by the NADH to lactate,
by Lactate dehidrogenase enzyme Lactate dehydrogenase Lactate
dehydrogenase Pyruvate + NADH + H + Lactate + NAD + - Oxidation 1
mol glucose via anaerobically glycolysis 2 mol ATP - Oxidation 1
mol glucose via anaerobically glycolysis 2 mol ATP
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ANAEROBICALLY GLYCOLYSIS : Respiratory chain is absence
Respiratory chain is absence Reoxidation of NADH NAD + via
Respiratory chain is inhibited Reoxidation of NADH NAD + via
Respiratory chain is inhibited Reoxidation of NADH via lactate
formation allows glycolysis to proceed in the absence of oxygen by
regenerating sufficient NAD + Reoxidation of NADH via lactate
formation allows glycolysis to proceed in the absence of oxygen by
regenerating sufficient NAD +
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GLYCOLYSIS IN ERYTHROCYTE Erythrocyte lack mitochondria
respiratory chain and Krebs cycle are absence Erythrocyte lack
mitochondria respiratory chain and Krebs cycle are absence Always
terminates in lactate Always terminates in lactate In mammals the
reaction catalyzed by phosphoglycerate kinase may be bypassed by a
process that catalyzed Biphosphoglycerate muta- In mammals the
reaction catalyzed by phosphoglycerate kinase may be bypassed by a
process that catalyzed Biphosphoglycerate muta- se se Its does
serve to provide 2,3-biphosphoglycerate Its does serve to provide
2,3-biphosphoglycerate bind to hemoglobin decreasing its affinity
for oxygen oxygen readily available to tissues bind to hemoglobin
decreasing its affinity for oxygen oxygen readily available to
tissues
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GLYCOLYSIS IN ERYTHROCYTE
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OXIDATION OF PYRUVATE Occur in mitochondria Occur in
mitochondria Oxidation of 1 mol Pyruvate 1 mol Asetyl- CoA + 3 mol
ATP Oxidation of 1 mol Pyruvate 1 mol Asetyl- CoA + 3 mol ATP CH 3
COCOOH + HSCoA + NAD + CH 3 CO-SCoA + NADH CH 3 COCOOH + HSCoA +
NAD + CH 3 CO-SCoA + NADH (Pyruvate) (Asetyl-CoA) (Pyruvate)
(Asetyl-CoA) Catalyzed by Pyruvate dehydrogenase enzyme Catalyzed
by Pyruvate dehydrogenase enzyme This enzyme need CoA as coenzyme
This enzyme need CoA as coenzyme In Thiamin deficiency, oxydation
of pyruvate is impaired lactic and pyruvic acid In Thiamin
deficiency, oxydation of pyruvate is impaired lactic and pyruvic
acid
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OXIDATION OF PYRUVATE
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GLYCOGENESIS Synthesis of Glycogen from glucose Synthesis of
Glycogen from glucose Occurs mainly in muscle and liver cell Occurs
mainly in muscle and liver cell The reaction : The reaction :
Glucose Glucose-6-P Glucose Glucose-6-P Hexokinase / Glucokinase
Hexokinase / Glucokinase Glucose-6-P Glucose-1-P Glucose-6-P
Glucose-1-P Phosphoglucomutase Phosphoglucomutase Glucose-1-P + UTP
UDPG + Pyrophosphate Glucose-1-P + UTP UDPG + Pyrophosphate UDPG
Pyrophosphorylase UDPG Pyrophosphorylase
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GLYCOGENESIS Glycogen synthase catalyzes the formation of -
1,4-glucosidic linkage in glycogen Glycogen synthase catalyzes the
formation of - 1,4-glucosidic linkage in glycogen Branching enzyme
catalyzes the formation of - 1,6-glucosidic linkage in glycogen
Branching enzyme catalyzes the formation of - 1,6-glucosidic
linkage in glycogen Finally the branches grow by further additions
of 1 4-gucosyl units and further branching (like tree!) Finally the
branches grow by further additions of 1 4-gucosyl units and further
branching (like tree!)
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SYNTHESIS OF GLYCOGEN
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GLYCOGENESIS AND GLYCOGENOLYSIS PATHWAY
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Glycogenesis Glycogenolysis
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GLYCOGENOLYSIS The breakdown of glycogen The breakdown of
glycogen Glycogen phosphorilase catalyzes cleavage of the 1 4
linkages of glycogen to yield glucose-1- phosphate Glycogen
phosphorilase catalyzes cleavage of the 1 4 linkages of glycogen to
yield glucose-1- phosphate (14)(14) glucan transferase transfer a
trisaccharides unit from one branch to the other (14)(14) glucan
transferase transfer a trisaccharides unit from one branch to the
other Debranching enzyme hydrolysis of the 16 linkages Debranching
enzyme hydrolysis of the 16 linkages The combined action of these
enzyme leads to the complete breakdown of glycogen. The combined
action of these enzyme leads to the complete breakdown of
glycogen.
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GLYCOGENOLYSIS Phosphoglucomutase Phosphoglucomutase
Glucose-1-P Glucose-6-P Glucose-1-P Glucose-6-P
Glucose-6-phosphatase Glucose-6-phosphatase Glucose-6-P Glucose
Glucose-6-P Glucose Glucose-6-phosphatase enzyme a spesific enzyme
in liver and kidney, but not in muscle Glucose-6-phosphatase enzyme
a spesific enzyme in liver and kidney, but not in muscle
Glycogenolysis in liver yielding glucose export to blood to
increase the blood glu- Glycogenolysis in liver yielding glucose
export to blood to increase the blood glu- cose concentration cose
concentration In muscle glucose-6-P glycolysis In muscle
glucose-6-P glycolysis
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GLUCONEOGENESIS Pathways that responsible for converting
noncarbohydrate precursors to glucose or glycogen Pathways that
responsible for converting noncarbohydrate precursors to glucose or
glycogen In mammals occurs in liver and kidney In mammals occurs in
liver and kidney Major substrate : Major substrate : 1. Lactic acid
from muscle, erythrocyte 1. Lactic acid from muscle, erythrocyte 2.
Glycerol from TG hydrolysis 2. Glycerol from TG hydrolysis
3.Glucogenic amino acid 3.Glucogenic amino acid 4. Propionic acid
in ruminant 4. Propionic acid in ruminant
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Gluconeogenesis meets the needs of the body for glucose when
carbohydrate is not available from the diet or from glycogenolysis
Gluconeogenesis meets the needs of the body for glucose when
carbohydrate is not available from the diet or from glycogenolysis
A supply of glucose is necessary especially for nervous system and
erythrocytes. A supply of glucose is necessary especially for
nervous system and erythrocytes. The enzymes : The enzymes : 1.
Pyruvate carboxylase 1. Pyruvate carboxylase 2. Phosphoenolpyruvate
karboxikinase 2. Phosphoenolpyruvate karboxikinase 3. Fructose
1,6-biphosphatase 3. Fructose 1,6-biphosphatase 4.
Glucose-6-phosphatase 4. Glucose-6-phosphatase
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GLUCONEOGENESIS
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GLUCONEOGENESIS FROM AMINO ACID
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GLUCONEOGENESIS FROM PROPIONIC ACID
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CORY CYCLE
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HMP SHUNT/HEXOSE MONO PHOSPHATE SHUNT = PENTOSE PHOSPHATE
PATHWAY An alternative route for the metabolism of glucose It does
not generate ATP but has two major function : 1. The formation of
NADPH synthesis of fatty acid and steroids 2. The synthesis of
ribose nucleotide and nucleic acid formation
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HMP SHUNT Active in : liver, adipose tissue, adrenal cortex,
thyroid, erythrocytes, testis and lactating mammary gland Its
activity is low in muscle In erythrocytes : HMP Shunt provides
NADPH for the reduction of oxidized glutathione by glutathione
reductase reduced glutathi- one removes H2O2 glutathione
peroxidase
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HMP SHUNT Glutathione reductase G-S-S-G 2-G-SH (oxidized
glutathione) (reduced glutathione) Glutathione peroxidase 2-G-SH +
H2O2 G-S-S-G + 2H2O This reaction is important accumulation of H2O2
may decrease the life span of the erythrocyte damage to the
membrane cell hemolysis
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HMP SHUNT
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BLOOD GLUCOSE Blood glucose is derived from the : 1. Diet the
digestible dietary carbohy- drate yield glucose blood 2.
Gluconeogenesis 3. Glycogenolysis in liver Insulin play a central
role in regulating blood glucose blood glucose Glucagon blood
glucose Growth hormone inhibit insulin activity Epinefrine stress
blood glucose