BIOCHEMISTRY • Proteins and Enzymes • Electrolytes and Acid-Base Balance • Case Studies PROTEINS and ENZYMES

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Erythrocyte Sedimentation Rate (ESR): A high ESR occurs when the body is infected or under stress, and the
liver is releasing acute-phase proteins into the blood.
ACUTE-PHASE PROTEINS: Proteins released by the liver when the body is under stress.
• alpha1-Antitrypsin: Protease inhibitor. When there is tissue damage, the dead tissue releases proteases, so
the anti-proteases help to prevent further damage.
• alpha2-Macroglobulin: Indirect anti-protease that fixes proteases and allows macrophages to engulf them.
• C-Reactive Protein (CRP): Opsonin, help to fix antibodies to antigen to facilitate phagocytosis.
• Ceruloplasmin: Copper-carrying protein, and anti-oxidant.
• Complement Proteins: Inflammatory mediators.
• Ferritin: Iron protein-carrier.
• Fibrinogen: Clotting factor.
• Haptoglobin: Binds to hemoglobin in blood.
• Serum Amyloid A Protein: Apolipoprotein.
PROTEIN ELECTROPHORESIS: alpha1, alpha2, beta, and gamma zones all have distinct proteins.
• alpha1 Zone: Closest to the anode (right).
o Albumin: Albumin is the tall peak closest to the anode.
 Normal properties:
 50% of liver protein production; primary determinant of oncotic pressure.
 20-day lifespan in circulation. If albumin decreases, it won't show up until 20
days later.
 MW = 68 kDa, which is right at the margin for glomerular filtration. That's why
even mild glomerular disease leads to albuminuria.
 Albumin is decreased under a lot of circumstances:
 Renal disease, proteinuria.
 Times of stress or disease.
 Malnutrition, Kwarshiorkor.
 Albumin binds to bilirubin and Ca+2.
 A decreased albumin levels can significantly alter the laboratory values for
bilirubin and calcium. If albumin is low, then these lab-values will be falsely
low, and you must adjust them upward to get the real value.
o Pre-Albumin: Fetal albumin is called pre-albumin. It consists of two proteins.
 alpha-Fetoprotein (AFP):
 Anencephaly, Spina Bifida: AFP leaks out of the fetus and into the maternal
circulation, thus AFP is increased in maternal blood.
 Liver Cancer, Endodermal Sinus (Yolk-Sac) Tumor: The tumors contain
immature tissue thxat releases pre-albumin, thus AFP is increased.
 Transtherytin: Fetal form of TBG that carries T3 and T4 in fetal blood.
• alpha2 Zone:
o alpha2-Macroglobulin: Huge molecule that binds to proteases and thus allows macrophages to
engulf them, getting rid of the proteases.
o Haptoglobin: Binds to free hemoglobin in the plasma. Its maximum binding-capacity is about
10% of all hemoglobin in blood.
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 If free haptoglobin is decreased (all bound up) and free hemoglobin is increased, then
that indicates intravascular hemolysis, such as that caused by blood-type incompatibility
or artifical heart valves.
o Ceruloplasmin
o GC Globulin
• beta Zone:
o LDL Lipoprotein
o Transferrin: Iron transporting protein.
o C3 Complement Factor
o beta2-Microglobulin: Part of the Major Histocompatibility Complex.
o Hemopexin: Binds free heme (hemoglobin degradation product) -- not hemoglobin itself, as in
Haptoglobin.
• gamma Zone: Closest to cathode (left).
o Immunoglobulins (Ig):
o C-Reactive Protein (CRP): Good marker during wound-healing. If it increases during woundhealing,
then the wound is probably getting infected.
 Originally discovered as a protein that binds to Streptococcus Pneumoniae.
o Fibrinogen:
o Lysozyme:
GAMMOPATHIES:
• Polyclonal Gammopathy: Broad gamma peak, indicating infection.
• Monoclonal Gammopathy: Narrow gamma peak. Differential:
o Multiple Myeloma, 60%. Malignancy of IgG-secreting plasma cells.
o Waldenstrom Macroglobulinemia, 10%. Hypersecretion of IgM.
o Lymphomas, Leukemias, 10%
o Monoclonal Gammopathy of Unknown Significance (MGUS), 10%
o Rare causes: Heavy chain disease, primary amyloidosis, solitary plasmacytoma.
• Hypogammaglobulinemia: No peak or shallow peak in gamma range.
o Due to inherited immune deficiency:
 X-Linked IgA Deficiency: Common, 1/750 births.
 Agammaglobulinemia: Rare.
o Acquired causes: Malignancies, immunosuppressive drugs, HIV, measles, malnutrition.
PLASMA ENZYMES:
• Alkaline Phosphatase (Alk.Phos.): Increased Alk.Phos. indicates:
o Cholestasis
o Increased bone growth or reformatuion. Osteoblasts secrete Alk.Phos.
• Alanine Aminotransferase (ALT): Increased ALT indicates liver damage. It is released into circulation
from damaged or necrotic liver cells.
• Aspartate Aminotransferase (AST): AST is released from a variety of damaged cells. Increased ALT
indicates:
o Liver damage
o Post-MI
o General cellular injury.
• Myocardial Infarct (MI): CAL is a mnemonic to remember the order in which enzymes increase:
o Creatinine Kinase (CK): 4-8 hrs. post-MI
o Aspartate Aminotransferase (AST): Goes up next.
o Lactate Dehydrogenase (LDH): Last one to go up.
• Creatinine Kinase (CK): Isozymes
o CK-MM: 99% of skeletal muscle, and about 77% of myocardium.
o CK-MB: About 22% of myocardium, but it is not found in any other tissues, so CK-MB is a
significant marker for myocardial infarct.
o CK-BB: Forms greater than 90% of CK in other tissues, such as CNS, colon, and ileum.
• Lactate Dehydrogenase (LDH): Isozymes
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o LDH-1: The predominant isozyme in myocardial tissue. High LDH-1 indicates MI.
• LDH-Flip: LDH-5 is normally highest, but in cases of MI LDH-1 may be higher. This is called an LDHflip
and is suggestive of MI.
o LDH-2 thru LDH-4: Minor isozymes.
o LDH-5: The predominant isozyme in liver and skeletal muscle. It is normally the highest, except
in cases of MI LDH-1 may be higher.
PROTEINURIA: Can be caused by three mechanisms:
• OVERFLOW:
o Normal proteins in blood: hemoglobinuria, myoglobinuria.
o Abnormal proteins in blood: Bence-Jones protein (IgG light-chains found in Mutiple Myeloma).
• GLOMERULAR: Primarily albuminuria.
o Fever, glomerulonephritis cause higher renal permeability.
o Altered hemodynamics (such as exercise) can transiently cause proteinuria.
• TUBULAR:
o Tubular damage due to heavy-metal poisoning, drug toxicities.
o Interstitial nephritis, pyelonephritis.
o beta2 and alpha1 Microglobulin will be found in urine. They are normally filtered and
reabsorbed, but with tubular disease they won't be reabsorbed.
ELECTROLYTES and ACID-BASE
TOTAL BODY WATER:
• TBW is normally 60% of body weight. 60% of 70 kg = 42L
o INTRACELLULAR: Intracellular fluid is normally two thirds of TBW. 67% of 42L = 28L
o EXTRACELLULAR: Extracellular fluid is normally one third of TBW. 33% of 42L = 14L
 PLASMA VOLUME: Plasma is normally about 5% of TBW. 5% of 42L = 2-3L
 INTERSTITIAL VOLUME: ISF is the rest of the volume. 14L - 3L = 10-11L.
POTASSIUM: Reference range 3.5 - 5.0 mEq / L
• HYPOKALEMIA: Decreased K+ in plasma
o Hypokalemia is usually accompanied by metabolic alkalosis.
• HYPERKALEMIA: Increased K+ in plasma
o Hyperkalemia is usually accompanied by metabolic acidosis.
SODIUM: Reference range 135 - 146 mEq / L
• HYPONATREMIA:
o Pitting Edema: Fluid has moved from vascular space into interstitial space. The intracellular
spaces are not affected.
 It occurs because of an off-balance of Starlnig's Forces:
 Too much hydrostatic pressure: CHF
 Too little oncotic pressure: Nephrotic Syndrome, Liver Cirrhosis
 One usually finds hyponatremia with these conditions, because the patient has
gained more water than sodium, so the sodium levels are diluted.
o Cerebral Edema: In hyponatremia, water enters into neuron cells in brain ------> cerebral edema.
Potential for herniation if it is not corrected.
 Idiogenic Molecules are osmotically active molecules created by the cerebrum, to try to
compensate for the cerebral edema. They are excreted into the ISF to try to suck the
water out of the cells.
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o Syndrome of Inappropriate ADH (SIADH): It is the most common cause of hyponatremia with
a normal physical exam (no edema, no lost skin turgor).
 CAUSES: Ectopic production by a tumor, such as small-cell carcinoma of the lung.
 TREATMENT: Restrict intake of water. Electrolyte balance remains normal; no
electrolyte adjustments are needed. Treat with ADH antagonists.
• HYPERNATREMIA:
o Dehydration: Pure water loss, infantile diarrhea.
 TREATMENT: Don't give the calculated amount of fluid back to the patient. Always
give less, to prevent cerebral herniation. The brain will make osmotically active idiogenic
molecules to try to compensate for the dehydration. Then if you give too much fluid, the
brain can herniate.
o Diabetic Ketoacidosis (DKA):
 Due to increased osmotic force of hyperglycemia, fluid will move from the intracellular
space into the plasma.
 Sodium Concentration must be adjusted for the presence of hyperglycemia (which isn't
normally taken into account). The sodium concentration will be actually higher than what
is reported. This is true with blood sugar > 500.
• TOTAL BODY SODIUM (TBNa):
o Decreased TBNa ------> decreased fluid in interstitial space ------> decreased skin turgor. You
can pull on skin and it isn't as elastic or tight.
o Increased TBNa ------> increased fluid in interstitial space ------> pitting edema. Fluid
accumulated in interstitial space.
 Patient may still have Hyponatremia, because the sodium concentration in blood is
decreased. But, the total body sodium will be increased.
DEHYDRATION:
• Adult Diarrhea is isotonic, thus adult dehydration will show normal sodium levels.
o To rehydrate, give them what they lost -- an isotonic saline solution.
• Infantile Diarrhea is hypotonic, thus infantile diarrhea will show hypernatremia.
o To rehydrate, give them what they lost -- a pedialyte, or hypotonic saline solution.
EDEMA:
• Cellular Edema: Tissue Hypoxia leads to cellular edema. Hypoxia ------> Na+/K+-ATPase Pump failure --
----> Na+ collects inside cells and brings water with it ------> hydropic swelling of cells and cellular
edema.
• Pitting Edema: CHF, Nephrosis, Cirrhosis lead to pitting edema. Transudate collects in interstitial space,
either due to increased hydrostatic pressure (CHF) or decreased oncotic pressure (Nephrosis, cirrhosis,
malnutrition).
• Cerebral Edema: In hyponatremia, water enters into neuron cells in brain ------> cerebral edema. Potential
for herniation if it is not corrected.
o Idiogenic Molecules are osmotically active molecules created by the cerebrum, to try to
compensate for the cerebral edema. They are excreted into the ISF to try to suck the water out of
the cells.
OSMOLALITY: Normal value is about 289 mOsm.
ACID-BASE:
• METABOLIC ACIDOSIS: Decrease the HCO3
- ------> the pH goes down. Compensation: Respiratory
Alkalosis will bring the pH back near normal.
• METABOLIC ALKALOSIS: Increase the HCO3
- ------> the pH goes up. Compensation: Respiratory
Acidosis (hypoventilation) can help to bring the pH back near normal.
o CAUSES:
 Vomiting: Lose enough stomach acid to produce alkalosis.
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 Diuretics: Loop diuretics and thiazides can lead to hypokalemia ------> secondary
metabolic alkalosis.
• RESPIRATORY ACIDOSIS: Increase the PCO2 ------> the pH goes down. Hypoventilation.
Compensation: Metabolic Alkalosis can help bring the pH back near normal.
• RESPIRATORY ALKALOSIS: Decrease the PCO2 ------> the pH goes up. Hyperventilation.
Compensation: Metabolic Acidosis can help bring the pH back near normal.
ANION GAP: Essentially, the difference between between the concentrations of cations (Na+ primarily) and anions
(Cl-, HCO3
-) in the blood.
• High Anion Gap: Metabolic Acidosis. It indicates that you have added acids to the blood: salicylic acid,
formic acid, lactic acid, oxalic acid, sulfuric acid.
• Normal Anion Gap: Respiratory Acidosis. It occurs when you ultimately become acidotic because of
losing HCO3
-.
NORMAL VALUES of ARTERIAL BLOOD-GASES:
Item Value
pH 7.4
[HCO3
-] 22 - 28 mEq / L
PaCO2 33 - 44 mEq / L
PaO2 90 - 100 mEq / L
CASE STUDIES
ACID-BASE CASE STUDIES:
Case # pCO2 PO2 HCO3
- pH Explanation
Case 1 70 low 27 7.2 Acute Barbiturate Overdose. PCO2 is high ------> respiratory acidosis from
hypoventilation. It is uncompensated because the HCO3
- is normal and the
pH is low.
Case 2 70 100 12 7.0 Code Arrest. High PCO2 ------> respiratory acidosis. Also, low HCO3
- ------
> metabolic acidosis. It's a mixed disorder.
Case 3 59 50 31 7.34 COPD. Partially compensated respiratory acidosis. High PCO2, high HCO3
-
(metabolic alkalosis) in compensation, near normal but slightly low pH.
Case 4 29 100 22 7.50 Hyperventilation. Uncompensated respiratory alkalosis.
Case 5 50 80 12 7.27 Chronic Renal Failure. Patient shows partially compensated metabolic
acidosis with high anion gap. Patient can't excrete all the acid he is creating.
Case 6 50 80 42 7.52 Diuretics in a non-smoking female. Metabolic Alkalosis (high HCO3
-) with
partially compensated respiratory acidosis (low PCO2).
Case 7 62 50 36 7.37 COPD, loop diuretic. Mixed disorder. Respiratory acidosis from COPD, and
metabolic alkalosis from loop diuretic. The pH is near normal but it should
not be called compensated, because full compensation never occurs, and the
pH is the result of two unrelated processes.
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CLINICAL BIOCHEMISTRY CASE STUDIES:
Case Pertinent Lab Values Explanation
1 Potassium Lab Error, Addison's
Disease
High K+
High Urea
Low Na+
K+ was high becuase of partial hemolysis of blood,
because blood was aged. Labs could indicate
Addison's Disease, but they need to be retaken.
2 Potassium Lab Error High K+ K+ of 45 is incompatible with life.
3 IDDM Glucose tolerance test: young kid most likely has a
transitory hyperglycemia, because he just ate. Next
day glucose is normal
4 Starvation, Dehydration ICF and ECF will shrink to the same extent.
Drink seawater: death due to hypernatremia,
diarrhea from magnesium in the sea-water.
5 Dehydration High Na+, high Cl-
High urea (pre-renal
failure)
Low HCO3
- (acidosis)
Man lost pure water ------> dehydration with
hypernatremia. He had hypotension, high pulse.
Pre-renal failure: Due to inadequate perfusion of
kidneys; uremia (high urea) is more prominent
than high creatinine.
6 Paraneoplastic SIADH Low serum osmolality,
low urine osmolality.
Low Na+, low Cl-
High K+ (aldosterone is
not being secreted at
all)
Differential should include Diabetic Ketoacidosis.
7 Dehydration High urea
All electrolytes are low.
Low HCO3
-, acidosis.
Uremia: pre-renal failure due to hypotension.
These labs would not be found in end-stage kidney
failure.
8 Injury with Lactic Acidosis High Na+
High K+
Low HCO3
-, metabolic
acidosis
Hyperkalemia is often associated with metabolic
acidosis.
Give calcium chloride immediately to prevent
arrhythmias associated with the hyperkalemia.
9 Volume depletion after surgery Low Na+ Her sodium was depleted from surgery. Her
responses to the low sodium included all things
except reduced GFR.
10 Creatinine Clearance Erroneous collection of urine is most common
mistake in measuring creatinine.
11 Diabetes Insipidus Normal electrolytes
(more or less).
Lack of ADH. ADH effects osmolality and plasma
volume, but not electrolyte balance.
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(more or less).
High serum osmolality.
Low urine osmolality.
volume, but not electrolyte balance.
12 Septicemia with acidosis, prerenal
failure
High K+
High urea
High serum osmolality
High K+ is associated with acidosis. Renal
disturbance is due to pre-renal failure. Serum urea
is also increased because patient is in a state of
excessive catabolism.
13 Renal Osteodystrophy High urea, high
creatinine
Chronic renal failure ------> low, calcium and
Vitamin-D ------> high PTH.
14 Compensated Metabolic
Alkalosis
High HCO3
- (alkalosis),
low PCO2
(compensatory
acidosis).
pH is high, but variable.
Low K+
Patient had severe vomiting, and later had shallow
respirations.
Low K+ is associated with alkalosis.
15 Respiratory Acidosis High PCO2 (respiratory
acidosis).
High HCO3
-
(compensatory
alkalosis)
16 Compensated Respiratory
Acidosis
High PCO2 (respiratory
acidosis).
High HCO3
-
(compensatory
alkalosis)
pH is closer to normal, hence compensated.
17 Diuretic-induced hypokalemia
with Metabolic Alkalosis
Low K+
High HCO3
-
18 Membranous Nephropathy,
Albuminuria
Albuminuria
19 Multiple Myeloma Hypercalcemia
20 Myocardial Infarct Increased CK, AST,
LDH.
Creatinine Kinase MB (CK-MB) is most useful
isoenzyme for diagnosis.
21 Metastatic Breast Cancer High Alk.Phos, AST,
ALT.
Normal albumin
Cancer metastases to bone.
22 Obstructive Jaundice, caused by
Carcinoma of Head of Pancreas
Very high alk.phos,
indicated of cholestasis.
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High AST and ALT
High Bilirubin
23 Acute Viral Hepatitis Very high AST and
ALT
Moderate Alk.Phos.
High gamma-GT
Dark color of urine is due to conjugated bilirubin.
Patient should recover from the hepatitis without
consequences.
24 NIDDM glucose tolerance test
25 Diabetic Ketacidosis Odor on breath
26 Nocturnal Hypoglycemia in a
Diabetic
Low blood sugar at
night after taking
insulin.
Measuring blood sugar during a hypoglycemia
attack isn't practical. Can measure catecholamines
in the blood to estabolish diagnosis.
Treatment: adjust insulin levels.
27 Osteomalacia Low Ca+2
Low adjusted Ca+2
High alk.phos. would be found if ordered, to
establish diagnosis.
28 Paraneoplastic Hypercalcemia High Ca+2
Low phosphate
Normal PTH
Normal PTH was found on further investigation,
so they took X-rays looking for metastases.
29 Hypomagnesemia with
scondary Hypoparathyroidism.
Low Mg+2
Low PTH secondarily
Mg+2 is required for PTH secretion!
30 Paget's Disease of Bone High alk.phos.
31 Lactotrope Adenoma with Panhypopituitarism
High Prolactin
The rest of the pituitary
hormones are low
Compression atrophy of the rest of the pituitary.
32 Possible Growth Deficiency Repeat test. GH levels can fluctuate, and erroneous
results can happen after a single random
measurement.
33 Cystic Cold Thyroid Nodule in
woman on ERT.
High T4
Low TSH
Taking estrogen ------> TBG is higher ------> T4
baseline must be higher to compensate for the
increased TBG.
Perform fine-needle aspiration biopsy to evaluate
the nodule.
34 Hypothyroidism
35 Thyrotoxicosis Order free T3 and T4 tests to evaluate status.
36 Acute Adrenal Cortical Failure Low Na+, High K+ Low Na+ and high K+ result from no aldosterone.
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Hypotension
Acidosis
Acidosis is secondary to the hyperkalemia.
Give ACTH (Synachten) test to confirm diagnosis.
37 Auto-immune Adrenalitis
(Addison's Disease)
Low Na+, High K+
Hypotension
Acidosis
38 ACTH-Secreting Carcinoma of
Lung, Cushing's Disease
Carcinoid tumor.
39 Polycystic Ovary Syndrome High testosterone, High
LH, low FSH
40 Chronic Malnutrition Vitamin-K malabsorption
41 Pernicious Anemia with
Hypothyroidism
42 Total Parenteral Nutrition,
secondary hyperglycemia
High blood sugar Can see hyperglycemia in patients who are on
TPN, due to poor or no stimulation of insulin
release.
43 MVA with tissue injury High K+ High K+ is released from tissues, from tissue
injury.
Measure creatinine kinase to document muscle cell
necrosis (rhabdomyolsysis).
44 Osteomalacia High alk.phos.
Low Ca+2, low Vit-D
Most likely caused y malnutrition, or
malabsorption of Vitamin-D.
45 Iron-Deficiency Anemia Low Fe+2
Low transferrin
saturation (high binding
capacity)
Low ferritin.
46 Wilson's Disease Liver failure.
47 Digoxin Toxicity, Renal Failure Patient had elevated serum urea due to pre-renal
failure, secondary to heart failure.
48 Salicylate Poisoning Low HCO3
-
High anion gap
Metabolic Acidosis with Respiratory Alkalosis.
Anion gap is increased because it is metabolic
acidosis.
49 Lead Poisoning Measure protoporphyrin in blood cells to confirm
diagnosis.
50 Alcoholism There is no lab test that is specific for alcoholism.
gamma-GT comes close but is not diagnostic.
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51 Diabetic Hypoglycemia after
drinking alcohol
Patient was hypoglycemia, due to mixing alcohol
with insulin. Treat with IV glucose.
52 Hyperlipidemia Low electrolytes
High amylase
High triglycerides
Pseudohyponatremia: Low Na+ due to abnormally
low water-content of plasma (i.e. plasma had way
too much lipid in it).
Genetic disorder involves Apolipoprotein-B
Patient is at risking of forming a volvulus.
53 Obesity, hyperlipidemia,
NIDDM, Alcohol
High cholesterol, lipids
High glucose
High gamma-GT
Treat with dietary measures. Man is at increased
risk for coronary artery disease.
54 Heterozygous Familial
Hypercholesterolemia
High fasting
cholesterol, Normal
lipids, Low HDL
Hypercholesterolemia is also found in patients
with Hypothyroidism.
55 Pheochromocytoma VMA in urine.
HTN
56 ACTH-secreting tumor,
Cushing's Disease
High HCO3
-
Low K+, High Na+
High creatinine
Metabolic Alkalosis secondary to hypokalemia,
from increased aldosterone activity.
Probably comes from oat-cell carcinoma of lung.
57 Alcoholic Liver Disease,
Hepatoma
High liver enzymes
High gamma-GT
alpha-Fetoprotein was normal in this case (it's
usually elevated)
Can also measure Carcinoembryonic Antigen
(CEA)
58 Thyroid Carcinoma Severe headache
High Ca+2
59 Septic Arthritis posing as Gout Uric acid came back normal.
Give antibiotics to treat septic arthritis.
60 Hemolysis, Tissue Damage High LDH, high CK
Low haptoglobin
LDH, CK = damage to: muscle, liver, or
erythrocytes.
61 Cystic Fibrosis High Cl- in sweat
62 Rh-Incompatibility Disease Measure bilirubin in amniotic fluid to diagnose
erythroblastosis fetalis. High bilirubin would
indicate hemolysis in the fetal blood.
63 Pre-Eclampsia Progressive
albuminuria, HTN
64 Cretinism Baby came back normal. TSH must be above 100
before follow-up test is required.
65 IRDS in premature infant