Biochemistry π§ͺ Flashcards
What happens to old RBCs after approximately 120 days in the circulation?
- After approximately 120 days in the circulation, old RBCs are taken up and degraded by the reticuloendothelial system (macrophages) particularly in the liver, spleen and bone marrow.
- The globin is degraded to amino acids β reutilized by the body. β’ Heme releases:
- iron β returns to the bodyβs iron stores.
- tetrapyrrole component β converted to biliverdin, then to bilirubin.
How is bilirubin carried in blood?
βBilirubin is lipid solubleβ
- Carried in the blood by albumin β unconjugated (indirect) bilirubin.
Where is bilirubin uptakin and conjugated?
βWith glocuronic acidβ
- Uptaken & conjugated in the liver β conjugated (direct) bilirubin.
Where is bilirubin excreted?
- Excreted in the bile.
What is jaundice?
- Jaundice is a yellow discoloration of membrane due to an increase in the level of blood bilirubin (hyperbilirubinemia) beyond normal level.
What are the normal levels for total bilirubin and direct bilirubin?
β Normal total bilirubin β up to 1 mg/dl. βToo lowβ
β Normal direct bilirubin β up to 0.25 mg/dl.
What are the types of jaundice?
Hemolytic (Prehepatic) jaundice
Hepatocellular (Hepatic) jaundice
Obstructive (Posthepatic) jaundice
What is the biochemical basis of hemolytic (prehepatic) jaundice?
βDue to excess hemolysis of RBCsβ
- Excess production of bilirubin exceeding the capacity of hepatocytes for uptake, conjugation and excretion
What is the type of raised bilirubin in hemolytic jaundice?
Unconjugated (indirect)
What are the causes of hemolytic jaundice?
- G-6-P-D deficiency
- Sickle cell anemia
- Incompatible blood transfusion
What is the biochemical basis of hepatocellular (hepatic) jaundice?
- Hepatocyte dysfunction β impaired hepatic uptake, conjugation or secretion of bilirubin
What is the type of raised bilirubin in Hepatocellular (Hepatic) jaundice?
- Both unconjugated & conjugated (direct & indirect)
What are the causes of Hepatocellular (Hepatic) jaundice?
- Infection (viral hepatitis)
- Liver cirrhosis
What is the biochemical basis of Obstructive (Posthepatic) jaundice?
- obstruction in the passage of conjugated bilirubin from the liver to the intestine β regurgitation of bilirubin to blood
What is the type of raised bilirubin in Obstructive (Posthepatic) jaundice?
Conjugated (direct)
What are the causes of Obstructive (Posthepatic) jaundice?
- Tumor βpancreas cancerβ
- Bile stones
What is the importance of estimation of Bilirubin levels?
β Used to assess presence of jaundice and to detect type of jaundice
β One of liver function laboratory tests ( used to assess excretory function of the liver
What are liver function laboratory tests?
β TOTAL PROTEIN
β ALBUMIN
β BILIRUBIN - TOTAL/DIRECT/INDIRECT
β LIVER ENZYMES β SGOT (AST) βSGPT(ALT) βtheir presence in plasma indicates problemsβ
What is the principle of colorimetric estimation of bilirubin Level
- Bilirubin reacts with diazotized sulfanilic acid to form a red colored azobilirubin.
- The intensity of the color produced is directly proportional to the concentration of bilirubin in the sample.
How is reading of colorimetric estimation of total bilirubin level done?
- Measure the absorbance of sample against blank at wave length 578 nm (560-600 nm).
How is total bilirubin concentration calculated?
- Total bilirubin concentration (mg/dl) = A(sample) Γ 10.8
How is reading of colorimetric estimation of direct bilirubin level done?
- Measure the absorbance of sample against blank at wave length 546 nm (530-555 nm).
How is direct bilirubin concentration calculated?
- Direct bilirubin concentration (mg/dl) = A(sample) Γ 14.4
What does indirect bilirubin concentration equal?
- Indirect bilirubin can be calculated by subtracting direct bilirubin from total bilirubin.
What is the reference range of each of?
AST
CK
LDH
AST: 8-20 U/L
CK: 20-110U/L
LDH: 120-240U/L
What are cardiac biomarkers?
- Cardiac biomarkers are proteins from heart muscle cells that have leaked out into the bloodstream after an injury to the cardiac muscle
- Blood tests for them are used to detect damage to heart cells
What are examples of cardiac biomarkers?
ο 1-Creatine Kinase (CK-MB)
ο 2- Lactate Dehydrogenase
ο 3- Transaminases
ο 4- Troponin βnot an enzymeβ
What does creatine kinase catalyze?
- It is an enzyme that catalyzes phosphorylation of creatine To creatine phosphate
What are the subunits that form creatine kinase?
- CK is formed of 2 subunit
B βββ brain
M βββ Muscle
What does increase in creatine kinase indicate?
CK has 3 isoenzymes
1- CK BB which increases in brain tumors.
2- CK MB which increases in heart diseases.
3- CK MM which increases in skeletal muscle diseases.
- So, CK isoenzymes are clinically important to differentiate between brain, heart and skeletal muscle diseases
What is the significance of the short duration of creatine Kinase?
Since it has a short duration, it cannot be used for late diagnosis of acute MI but can be used to suggest infarction extension if levels rise again.
What are transaminases?
Transaminases are intracellular enzymes.
What is the levels in plasma of transaminases under normal conditions?
Their levels in plasma are low under normal
conditions.
What are types of transaminases and where are they present?
There are two types of transaminases:-
1- Alanine transaminases (ALT or GPT) is present mainly in the cytoplasm of liver .
2- Aspartate transaminases (AST or GOT) is present in
both cytoplasm and mitochondria in liver, heart, and skeletal muscles.
Which transaminase increases in case of myocardial infarction?
In MI there is an increase in AST or GOT.
What is the effect of lactate dehydrogenase?
LDH is responsible for changing lactic acid into pyruvic acid
What are LDH isoenzymes?
LDH1 is formed of HHHH. It increases in myocardial infarction
LDH2 is formed of HHHM. It increases in myocardial infarction.
LDH3 is formed of HHMM. It increases in leukaemia.
LDH4 is formed of HMMM. It increases in viral hepatitis.
LDH5 is formed of MMMM. It increases in viral hepatitis.
- So, LDH isoenzymes are clinically important to differentiate between heart, liver and blood diseases.
What are heart-specific isoenzymes of LDH?
LDH1 and LDH2 are called heart-type or heart-specific isoenzymes
Where are LDH1 and LDH2 normally found?
- LDH-1 isozyme is normally found in the heart muscle
- LDH-2 is found more in blood serum.
What is the most significant biomarker in diagnosis of myocardial infarction?
rise in LDH1 is the most significant in diagnosis of MI
What is the time of the start of rise in each of the following?
CK-MB
AST
LDH(heart-specific)
- 4-6h
- 6-8h
- 12-24h
What is the time of the peak of elevation in each of the following?
CK-MB
AST
LDH(heart-specific)
- 1 day
- 1-2 days
- 2-3 days
What is the duration in each of the following?
CK-MB
AST
LDH(heart-specific)
- 3-5 days
- 4-6 days
- 10-14 days
What are cardiac specific troponin I and Troponin T? And where are they normally present?
- Troponin is a type of protein found in the muscles of your heart.
- Troponin isnβt normally found in the blood.
- When heart muscles become damaged, troponin is sent into the bloodstream. As heart damage increases, greater
amounts of troponin are released in the blood.
Give a note about the levels of troponin.
elevated in the blood within 3 to 6 hours after heart injury and may remain elevated for 10 to 14 days.
Why is the level of LDH normal in a patient if the sample is taken after 12 hours of onset of chest pain?
As it starts to rise after 12-24h, so its level wouldnβt be elevated
What happens to enzymes Activity over time?
- With time the enzyme activity increase up to certain limits after which the activity well decrease due to accumulation of end products
- How is the concentration of biomarkers calculated?
What is the principle, procedure and calculation of the estimation of creatine kinase and lactate dehydrogenase?
Check the βestimation of cardiac biomarkes summaryβ
