Carbohydrate metabolism
BIOENERGETICS AND
METABOLISM
_ The characteristics of living organisms – their organization
complex and its capacity for growth and reproduction – are
resulting from biochemical processes coordinated.
_ Metabolism is the sum of all chemical transformations
that occur in living organisms.
_ There are thousands of biochemical reactions catalyzed by enzymes.
_ The functions of cell metabolism are:
1. Collection and use of energy;
2. Synthesis of structural and functional molecules;
3. Cell growth and development and
4. Removal of waste products
The met. It is divided into 2 parts:
· Anabolism: biossinetico are processes from simple precursor molecules and small. Anabolic pathways are reductive processes energon and q need power supply.
· Catabolism: are the proc. Degradation of nutrients and organic molecules of cellular components that are converted to simpler products with the release of energy. The catabolic pathways are proc. And oxidative exergonic.
Three stages of catabolism:
• 1 ° stage: the complex nutrient molecules (proteins, carbohydrates and lipids, non-steroids) are broken into smaller units, amino acids, monosaccharides and fatty gracxos + glycerol.
• 2 ° stage: the products of the 1st Stages are transformed into single units
• 3 rd stage: acetyl-CoA is oxidized in the citric acid cycle to CO2 as the coenzymes NAD + and FAD are reduced by 4 pairs of electrons to form a three NADH and FADH2. The reduced coenzymes transfer their electrons to CO2 through the mitochondrial electron transport chain, producing ATP and H2O in a proc. called Oxidative Phosphorylation.
Carbohydrates are:
– Monosaccharides: glucose, fructose, galactose
– Polysaccharides: starch, glycogen
– Disaccharides sucrose, lactose.
– Or are Poliidroxialdeídos poliidroxicetonas or
substances that release these compounds by hydrolysis.
– Are universal sources of nutrients and energy for the
Cells.
– It is the preferred fuel for the contraction
skeletal muscle.
Glycolytic pathway:
It is the central pathway of glucose catabolism
in a sequence of ten reactions
enzyme occurring in the cytosol
all human cells
Two phases:
– Preparatory Phase: 2 glyceraldehyde-3-P
– Phase of payment: 2 ATP, 2 NADH, 2 pirutavo
Functions of the glycolytic pathway
Convert glucose into pyruvate
Synthesize ATP with or without oxygen
Prepare to be glucose
completely degraded into CO2 and H2O
Allow the partial degradation of
glucose anaerobically
Intermediates for other biosynthetic processes
Control of the glycolytic pathway:
– Allosteric activation or inhibition;
– Covalent bonds;
– Control of enzymatic synthesis.
This from pyruvate:
– Synthesis of lactate (glycolysis under anaerobic conditions
– Acetyl-CoA (citric acid cycle)
– Oxaloacetate (gluconeogenesis)
– Alanine (amino acid synthesis)
Pyruvate Lactate ®:
This reaction is the main option used by the cells under
hypoxic conditions as in skeletal muscle submitted to
intense activity, for example, for the reoxidation of NADH
NAD + in the cytosol and thus to continue producing ATP by
glycolysis. The lactate formed in active muscle diffuses into the
blood and is transported to the liver where it is converted to glucose
through gluconeogenesis.
Some tissues such as erythrocytes, even under conditions
Aerobic, producing lactate as end product of glycolysis.
Glycogenesis
Glucose>> glycogen
It occurs in all animal tissues, predominantly
in the liver and muscles
Source of glucose in the period between meals
Liver: reservoir of glucose for the current
blood
Muscle: immediate source of energy
_The Glycogen is an immediate source of glucose to
muscles when there is a reduction of glucose
blood (hypoglycemia).
_O Is available glycogen in the liver and muscles,
being totally consumed about 24 hours
after the last meal.
Glycogenesis
storage form of glucose in the liver and muscle
glucose units joined by glycosidic bonds (a1 ® 4)
in the main chain and (a1 ® 6) branch points in
The glycogen is the substrate for UDP-glucose
Glycogen synthase requires a primer
Glycogenin protein is responsible for the formation of this
small chain. It binds the first residue of glucose
Glycogen synthase binds to the chain of glycogenin,
extending the glycan chain
Glycogenesis
Branch:
Every 8 to 14 glucose residues
Branching enzyme transfers from 6 to 7 residues
Connecting to (1 ® 6)
Glycogenolysis
Glycogen>> glucose
Glycogen phosphorylase acts with Mg2 + and pyridoxal-5-phosphate,
a derivative of vitamin B as a cofactor
Glycogenolysis
Desramificação
Transfer of a unit with three waste
Disruption of binding to (1 ® 4) with formation of
new route to (1 ® 4)
Disruption of binding to (1 ® 6) is the hydrolysis
same glycogen debranching enzyme
Glycogenolysis
Regulation of Glycogen Phosphorylase
a) Control hormonal
= epinephrine activates phosphorylase
= glucagon activates phosphorylase
b) allosteric control
= AMP activates phosphorylase
Ca2 + = active phosphorylase
= glucose inhibits phosphorylase
Degradation and synthesis are regulated
= coordinately regulating hormonal
– Insulin = active synthesis
> Active glycogen synthase
– = Active glucagon degradation
> Inhibits glycogen synthase
Biosynthesis
carbohydrates
Gluconeogenesis:
– Formation of new sugar
– Synthesis of glucose from precursors nãoglicídicos:
Lactate, pyruvate, glycerol and
Amino Acids (Alamin);
It occurs in all animals, plants, fungi and
Microorganisms.
Gluconeogenesis
– Brain and blood cells need blood glucose
as the main source of energy.
– Need daily blood glucose = 160 g, 120 g only for
brain;
* Glycogen provides 190 g of glucose, sufficient for a
days;
** Require longer periods of fasting glucose that is
synthesized from renewable non-glucidic
– In animals gluconeogenesis occurs primarily in the liver and to a lesser extent in the renal cortex.
– Gluconeogenesis is essential because the brain, nervous system, testes, erythrocytes, renal medulla and embryonic tissues using blood glucose as the sole source of energy.
– Glycolysis? Conversion of glucose to pyruvate
– Gluconeogenesis? Conversion of pyruvate to
glucose
Gluconeogenesis
– NO is the reversal of the reactions of the glycolytic pathway!
– 3 = different reactions are replacing the three reactions
irreversible glycolysis catalyzed by hexokinase,
1-phosphofructokinase and pyruvate kinase.
Gluconeogenesis:
– Deviation = 1, conversion of pyruvate to phosphoenolpyruvate
* Pyruvate is converted to oxaloacetate by pyruvate
Carboxylase in the mitochondria
– 2nd Deviation = conversion of fructose-1 ,6-bisphosphate to
fructose-6-phosphate
* Catalyzed by fructose-1 ,6-bisphosphatase.
– 3rd Deviation = conversion of glucose-6-phosphate glucose
* Catalyzed by glucose-6-phosphatase.
Pentose Phosphate:
1. Ribose 5-phosphate
– That makes up the pentose nucleic acids and coenzymes
– Formation of intermediates of glycolysis
2. Nicotinamide adenine dinucleotide (NADPH)
– Coenzyme reducing processes of synthesis
– Reaction against oxidative compounds
The energy derived from oxidation of glucose is stored as
reducing power (NADPH) and not for the synthesis of ATP
Pentose Phosphate:
occurs in the cytosol in two steps: step
oxidative phase and not? oxidation.
– In step oxidative glucose? 6? Phosphate is converted to
ribose? 5? phosphate accompanied by the formation of two molecules
NADPH.
– The step did not? Involves isomerization and oxidative condensation
of several different sugar molecules. Three intermediate
process are used in different ways: ribose? 5? phosphate, the
fructose? 6? phosphate and glyceraldehyde? 3? phosphate.
– Rapidly dividing cells (skin, bone marrow and
intestinal mucosa to synthesize RNA using pentoses,
DNA and ATP as coenzymes, NADH and FADH2
coenzyme A.
– Fabrics that make the synthesis of large amounts
fatty acids (liver, fat, glands
breast during lactation) or intense synthesis of
cholesterol and steroid hormones (liver, gland
adrenal glands, gonads) reductions in the use of NADPH
biosynthesis or defense against free radicals.
Pentose Phosphate
– The pentose phosphate pathway can be conceived as a deviation
for the production of fructose-6-phosphate from glucose 6-phosphate.
– Both glucose 6-phosphate and glyceraldehyde 3-phosphate
produced by the pentose phosphate pathway can be
metabolized to pyruvate and finally oxidized in the system
mitochondrial enzyme.
– All of the enzymes in the pentose phosphate pathway are located in
cytosol.
– The reactions of the non-oxidative reversible and thus can
convert hexose phosphate into pentose phosphate, the critical reaction
CO2 fixation by plants during photosynthesis.
Krebs Cycle:
– Citric acid cycle
– Oxidation of acetylic groups from acetyl CoA
– Generates NADH, FADH2, CO2 and high-energy electrons
Krebs Cycle:
It is the set of reactions that occurs in the mitochondrial matrix in order to provide substrates that are dehydrogenated and descaboxilados.
– When dehydrogenation occurs, there is activation of the respiratory chain (where we have the H2O and ATP synthesis which stores the energy released by the reaction until an appropriate time to use).
– When decarboxylation occurs, there is the release of CO2, the main metabolite of the Krebs cycle.
The beginning of the Krebs cycle begins with the entry of acetyl-CoA into mitochondria, the acetyl-CoA combines with a
acid called oxaloacetate via an enzyme called citrate synthase, after this event has been the output of
coenzyme (Hs-CoA) and the entry of H2O, giving rise to citrate by the enzyme aconitase in the same turn
isocitrate. For you see your isocitrate suffered the action of the enzyme isocitrate dehydrogenase that will make the removal of CO2 and H2
isocitrate to form a-ketoglutarate, the H2 drives that left the respiratory chain at the level of NADH2 which in turn produces
3 ATPs.
– The speed of the Krebs cycle and controlled by the amount of ATP formed, that is, the more ATP formed lower the speed of the cycle and the lower the amount of ATP formed increased the speed of the cycle.
– For each ck back in a molecule is used DEA cetyl-coA.
– In a back four are driven respiratory chains, and the formation of 12 ATP and of these one is the level of GTP.
– Two CO2 produced.
– Two O2 consumed.