Prepared By: Wong, F.M.B.
Carbohydrates
and Lipids
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CARBOHYDRATES
Carbohydrates
Composed of hydrogen, carbon, and oxygen (CHO)
Classified as Monosaccharides, Disaccharides, and Polysaccharides
GLUCOSE is the only carbohydrate to be directly used for energy or
stored as glycogen.
The brain is completely dependent on blood glucose for energy
production.
SUCROSE is the most common nonreducing sugar.
Pancreas (as an endocrine gland) secretes the hormones' insulin,
glucagon, and somatostatin from the cells in the islets of Langerhans.
Pancreas (as an exocrine gland) produces and secretes amylase
which is responsible for the breakdown of complex carbohydrates.
Glucose
Metabolism
The LIVER plays a major role in
the regulation of blood glucose
levels.
Glycolysis
Glycogenesis
conversion of glucose into lactate or pyruvate
conversion of excess glucose into glycogen in the liver for storage
Glycogenolysis
Lipogenesis
breaking down of stored glycogen to glucose for use as energy
conversation of carbohydrates to fatty acids
Lipolysis
conversation of fatty acids to carbohydrates
Regulation
of Blood
Glucose
Insulin
Glucagon
Somatostatin
Growth hormone
ACTH
Cortisol
Catecholamines
Thyroid hormones
Insulin
Growth Hormone
Glucagon
ACTH
Somatostatin
Cortisol
the only hypoglycemic hormone
synthesized by the B-cells of the
islets of Langerhans in the pancreas.
primary hyperglycemic hormone
synthesized by the a-cells of the
islets of Langerhans.
inhibits the action of insulin,
glucagon, and growth hormone. It is
produced by the delta cells of the
islets of Langerhans.
secreted by the anterior pituitary
gland (adenohypophysis).
produced by the anterior pituitary
gland (adenohypophysis).
secreted by the cells of the zona
fasciculata and zona reticularis of
the adrenal cortex.
Catecholamines
released from the chromaffin cells of
the adrenal medulla
Thyroid Hormones
produced by the thyroid glands
which promotes glycogenolysis,
gluconeogenesis, and intestinal
absorption of glucose
Glucose
Methodologies
CHEMICAL METHODS
Alkaline Copper Reduction
Method
Alkaline Ferric Reduction
Method
Condensation Method
ENZYMATIC METHODS
Glucose Oxidase Method
Hexokinase Method
Things to consider:
Fasting glucose in whole blood is 12-15% lower than in serum or plasma.
Glucose determinations are generally performed on serum or plasma rather than
whole blood.
more convenient because it does not require mixing
greater stability because glycolysis is minimized
Serum must be separated from the cells within 30 minutes.
Sodium fluoride (NaF) inhibits glycolysis.
At room temperature (20-25°C), glycolysis decreases glucoses by 7mg/dL/hr.
At refrigerated temperature (4°C), glucose is metabolized at the rate of about 2
mg/dL/hr.
As little as 10% contamination of 5% Dextrose will increase the glucose by 500mg/dL.
A. Chemical Methods
1. Alkaline Copper Reduction Method
a. Folin Wu - uses phosphomolybdenum blue as a reagent
b. Nelson Somogyi - most commonly used chemical method for glucose;
uses arsenomolybdenum blue
c. Neocuproine Method - yellow or yellow orange cuprous-neocuproine
complex
d. Benedict's Method - modification of Folin Wu; uses citrate or tartrate as
stabilizer
2. Alkaline Ferric Reduction Method
a. Hagedorn Jensen Method
b. Reduction of yellow ferricyanide to a colorless ferrocyanide
3. Condensation Method
a. Ortho-toluidine Method
b. Dubowski Method - chemical method that is still widely used today
B. Enzymatic Method
1. Glucose Oxidase Method
- measured B-D glucose
- MUTAROTASE: converts other form of glucose to B-D glucose
- coupled-enzymatic reaction
2. Hexokinase Method
- REFERENCE METHOD
- most specific method with an increased specificity due to glucose-6phosphate dehydrogenase (G6PD) derived from yeast (most specific
reagent)
- coupled enzymatic reaction
- requires protein free filtrate; for routine clinical use: serum is used directly
without deproteinization
Glucose
Measurement
Random Blood Sugar (RBS)
Glucose Tolerance Test
Fasting Blood Sugar (FBS)
Glycosylated Hemoglobin
(HbA1c)
2-Hour Post Prandial Blood Sugar
(2-Hours PPBS)
Fructosamine
Random Blood Sugar
- for emergency cases
- requested during insulin shock
- for patients with diabetic coma
Fasting Blood Sugar
- measure of overall glucose homeostasis
- achieved after 8-12 hours fasting
2-Hour Post Prandial Blood
Sugar
- 2 hours after eating
- measures how well the body metabolizes glucose
Glucose Tolerance Test
- multiple blood sugar test
- performed to diagnose gestational diabetes
Glycosylated Hemoglobin
- largest fraction of glycated hemoglobin A1
- specimen: EDTA whole blood
- reflects the average blood glucose level over the previous 2-4
months (120 days)
- monitors LONG-TERM GLUCOSE CONTROL
Fructosamine
- also known as glycated albumin or plasma protein ketoamine
- reflection of SHORT TERM GLUCOSE CONTROL (3-6 weeks)
- for monitoring patients with chronic hemolytic anemia, Hgb
variants Hgb S or Hgb C, and shortened RBC lifespan.
LIPIDS
Phospholipids | Cholesterol | Triglyceride | Lipoproteins
A. PHOSPHOLIPIDS
Similar to triglycerides in terms of structure
Composed of one glycerol and 2 fatty acid molecules
attached via ester bonds
Most abundant lipid; serves as major constituents of cell
membranes and outer shells of lipoprotein molecules
Acts as Lung Surfactant
L/S ratio of 2: Fetal Lung Maturity
L/S ratio of < 2: Respiratory Distress Syndrome, Infant's
Alveoli Collapse
Sphingolipids/Sphingomyelin - major lipids of the cell
membranes of the CNS
≥
B. CHOLESTEROL
Is an unsaturated steroid alcohol containing four rings, and it
has a single C-H side chain tail similar to fatty acid.
It is found on the surface of lipid layers; synthesized in the
liver
Not an energy source
2 Forms:
70% Esterified Form: fatty acid forms an ester bond at
carbon 3
30% Unesterified Form: no fatty acids attached to the ring
Precursor of 5 major classes of steroids: progestins,
glucocorticoids, mineralocorticoids, androgens, and
estrogen (ProGAME)
Considered as a secondary test for liver function and thyroid.
B. CHOLESTEROL
Reference values for Cholesterol
Normal or desirable: <200mg/dL
Borderline high: 200-239mg/dL
High: 240mg/dL
≥
Cholesterol
Methodologies
CHEMICAL METHODS
ENZYMATIC METHODS
REFERENCE METHOD
A. Chemical Methods
1. One-step Method
a. Colorimetry
b. Pearson, Stern and Mac Gavack
2. Two-step Method
a. Extraction, Colorimetry
b. Bloors
3. Three-step Method
a. Saponification, Extraction, Colorimetry
b. Abell - Kendal
4. Fourth-step Method
a. Precipitation, Saponification, Extraction, Colorimetry (PiSEC)
b. Schoenheimer Sperry
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A. Chemical Methods
1. Colorimetry
a. Liebermann Burchardt Reaction - uses Cholestedienyl Monosulfonic Acid;
green end color; most commonly used
b. Salkowski Reaction - uses Cholestedienyl Disulfonic Acid; red end color
2. Extraction - Petroleum Ether
3. Saponification - Alcoholic KOH
4. Precipitation - Acidic Solution
B. Enzymatic Methods
1. Cholesteryl Ester Hydrolase
a. Cholesterol Esters -> free cholesterol + fatty acids
2. Cholesterol Oxidase
- Reacts with free cholesterol only
- Routine method
- Most common method
C. Reference Method
1. Abell, Levy and Brodie Method
- Chemical Method
- Three-step Method
- Saponification: Alcoholic KOH
- Extraction: uses Hexane instead of Petroleum ether
- Colorimetry: Liebermann Burchardt Reagent
C. TRIGLYCERIDE
also known as triacylglycerol since it is composed of one
glycerol molecule with 3 fatty acid molecules
main storage lipid in man
constitutes 95% of all fats stored in adipose tissue
energy source and provides excellent insulation
C. TRIGLYCERIDE
Reference values for Triglyceride
Normal: <150mg/dL
Borderline high: 150-199mg/dL
High: 200-499mg/dL
Very high: 500mg/dL*
≥
*very high = acute pancreatitis
Triglyceride
Methodologies
CHEMICAL METHODS
ENZYMATIC METHOD
REFERENCE METHOD
A. Chemical Methods
1. Colorimetric Method
a. Van Handel and Zilversmith: (+) Blue color
2. Fluorometric Method
a. Hantzsch Condensation
B. Enzymatic Method
1. Coupled Enzymatic Reactions
a. Lipase: Triglyceride -> Glycerol + Fatty Acid
b. Glycerol Kinase
- Routine method
- Most common method
C. Reference Method
1. Modified Van Handel and Zilversmith
- chemical method: (+) pink product; original color is blue
D. LIPOPROTEINS
Please refer to next powerpoint
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