CARBOHYDRATES Flashcards
Immediate sources of energy for the body
CARBOHYDRATES
Provides structural integrity to cell membrane
CARBOHYDRATES
Determines antigenicity
CARBOHYDRATES
Extraneous origin
CARBOHYDRATES
Carbohydrates is classified into
Monosaccharides
Disaccharides
Polysaccharides
Under Monosaccharides
D-Glucose
D-galactose
D-fructose
is the most important of all the simple carbohydrates.
D-Glucose
hydrolyzed into 2 glucose units
Maltose
hydrolyzed into glucose and fructose
Sucrose
hydrolyzed into glucose and galactose
Lactose
Under Polysaccharides
Starch
Glycogen
Cellulose
Inulin (fructose units)
Carbohydrate measurements are important in diseases that result from abnormal carbohydrate metabolism such as
hypoglycemia and diabetes mellitus
Lactase deficiency will lead to
Lactose intolerance
Deficiency in either galactokinase or galactose phosphate-1-phosphate uridyl transferase will cause
galactosemia
galactosemia is screened using
Guthrie test and Beutler method.
Specimens used for carbohydrate measurements include
whole blood, plasma or serum.
needed for HbA1c determination.
Hemolysate
It is the only hormone that lowers blood glucose by inhibiting glycogenolysis and
gluconeogenesis in the liver and increasing glucose uptake by the peripheral tissues.
Insulin
Insulin lowers blood glucose by
inhibiting glycogenolysis and
gluconeogenesis in the liver and
increasing glucose uptake by the peripheral tissues.
It is produced by the beta-cells of the islets of Langerhans of the pancreas.
Insulin
It is inhibited by the scarcity of dietary fuels and during periods of trauma due to increased epinephrine levels.
Insulin
Active insulin comes from the cleavage of
C-peptide off the pro-insulin
has become a marker for endogenous production of insulin to differentiate it from exogenous insulin.
C-peptide
Elevated levels of C-peptide suggests
hyperinsulinism
Normal value of C-peptide
<1.2 ng/ml
The C-peptide to insulin ratio is expected to be
5:1
oppose many actions of insulin
Glucagon
hormones epinephrine
cortisol
GH
It increases glucose by stimulating glycogenolysis and gluconeogenesis in the liver.
Glucagon
It is produced by the alpha-cells of the islets of Langerhans of the pancreas.
Glucagon
It increases blood glucose by activating adenylate cyclase to produce cAMP which further activates the enzyme phosphorylase causing increased glycogenolysis .
Epinephrine
Like glucagon, it is responsible in the short-term glucose regulation.
Epinephrine
It is produced by the chromaffin cells of the adrenal medulla.
Epinephrine
It increases blood glucose primarily by stimulating gluconeogenesis by promoting
protein catabolism and deamination and it inhibits glucose metabolism in peripheral tissues.
Cortisol
Like the GH, it promotes long-term regulation of blood glucose.
Cortisol
It is produced by the fascicular cells of the adrenal cortex upon the stimulation by adrenocorticotropic hormone (ACTH).
Cortisol
It increases blood glucose by inhibiting uptake of glucose by cells and due to its
antagonistic action on insulin.
Growth Hormone
It is produced by the anterior pituitary gland
Growth Hormone
It increases blood glucose by stimulating glycogenolysis, accelerating degradation of
insulin and promoting absorption of glucose in the intestinal tract..
Thyroid Hormone
It is synthesized by the thyroid follicles of the thyroid gland.
Thyroid Hormone
It inhibits both insulin and glucagon.
Somatostatin
It is produced by the delta-cells of the islets of Langerhans of the pancreas.
Somatostatin
Normal value of Serum or plasma
50-110mg/dL (2.8–6.2mmol/L)
Normal value of Serum or plasma
50-110mg/dL (2.8–6.2mmol/L)
In serum or plasma, The conversion factor from mg % to mM is
0.055
lower than serum or plasma by 10% due to volume occupied by 1 RBCs during measurement
Whole blood
normal values for CSF
40–70 mg/dL (60– 75% of the level in serum or plasma)
Delay in glucose testing would require
fluoride or iodoacetate
to prevent glycolysis for 48 hours at 4 deg Celsius.
Two (2) mg of NaF per ml of whole blood
Reduction Methods
Copper Reduction Methods
Ferric Reduction Tests
Copper Reduction Methods
Folin-Wu
Somogyi-Nelson
Neocuproine
Benedict
Schaeffer-Hartmann-Somogyi
whole blood is deproteinized using 10% sodium tungstate and 2/3N sulfuric acid; cuprous oxide formed is allowed to react in a hot alkaline solution with phosphomolybdate reagent to produce phosphomolybdenum blue complex.
Folin-Wu
serum is deproteinized using 5% zinc sulfate and 0.3N barium hydroxide; the cuprous oxide formed is allowed to react with arsenomolybdate to produce arsenomolybdenum blue
Somogyi-Nelson
the deproteinization process of Somogyi-Nelson is able to remove
NGRS measuring true glucose value
End product of Folin-Wu
phosphomolybdenum blue complex
The end product of Somogyi-Nelson
arsenomolybdenum blue
adapted to automation; sample is deproteinized by tungstate or dialysis; cuprous oxide formed is allowed to react with neocuproine (2,9-d imethyl- 1, 10 phenanthroline hydrochloride) to form a yellow to orange product
Neocuproine
modification of Folin-Wu employed in testing urine sugars.
Benedict
titrimetric method using iodine to oxidize cuprous oxide formed and the excess iodine in the blank and the sample is titrated with thiosulfate.
Schaeffer-Hartmann-Somogyi
Under Ferric Reduction Tests
Hagedorn-Jensen
uses ferricyanide ions instead of cupric ions; the yellow ferricyanideis reduced to colorless ferrocyanide solution and the decrease in absorbance is monitored
Hagedorn-Jensen
offers advantage over cuprous ions by being less reoxidizable by air
ferrocyanide
Condensation Methods
Dubowski (Ortho-toluidine method)
Anthrone condensatio
glucose condenses with an aromatic amine, o-toluidine in hot glacial HAc to produce a green colored N- glycosylamine and a Schiff’s base
Dubowski (Ortho-toluidine method)
considered as the most specific nonenzymatic for glucose
Dubowski (Ortho-toluidine method)
glucose is converted into hydroxymethylfurfural in hot strong acid and reacts with the enol tautomer of anthrone to form a green product
Anthrone condensatio
Enzymatic Methods
Glucose Oxidase (GOD) Coupled Reaction
Polarographic GOD Method
converts glucose, in the presence of oxygen, into gluconic acid and hydrogen peroxide. In the presence of the enzyme peroxidase, a reduced chromogen is oxidized to give a colored compound; vitamin C interferes in the test.
GOD
oxidized to a quinone imine dye (pink
to red)
p-aminophenazone (PAP)
which is oxidized to an orange product
o-dianisidine
which is oxidized to a green product
o-toluidine
which is oxidized to a blue product
indophenol blue
which is oxidized into a purple product.
iodide
This is based on the consumption of oxygen during the enzyme catalysis of glucose conversion.
Polarographic GOD Method
The oxygen consumed in polarographic GOD method is monitored using a
Clark electrode (amperometric technique)
The most specific method and therefore the reference method for glucose determination.
Hexokinase Method
Glucose is phosphorylated in the presence of__________ to form glucose-6-phosphate
hexokinase and magnesium ions
a group of diseases in which blood glucose levels are elevated due to deficiency in insulin action.
Diabetes Mellitus
Classical manifestations (3 Ps) of Diabetes Mellitus
Polyuria
Polydipsia
Polyphagia
excessive urine volume
Polyuria
excessive thirst
Polydipsia
excessive eating
Polyphagia
