Biochemistry | Master Of Medicine

Category Archives: Biochemistry

Biochemical tests

  1. Fouchets test – bile pigments(urobilinogen and porphobilinogen)
  2. Hay’s Sulphur test- Bile salts
  3. Benedicts test – Blood sugar
  4. Rothera’s test – Ketone bodies
  5. Biuret test – Protein

Biuret reagent- CuSO4,Sodium potassium tartarate,Potassium iodide in sodium hydroxide

Test for glucose

  1. Benedict’s test
  2. Glucose oxidase test(Beta D glucose estimation-quantitative)
  3. Dextrostix test
  4. Follin and wu method

Glycogen storage disorders mnemonic

Glycogen storage diseases from1 to 6 can be remembered using the below mentioned mnemonic.

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  1. Von Gierke’s
  2. Pompe’s
  3. Cori’s
  4. Anderson’s
  5. McArdle’s
  6. Her’s

Anderson’s (IV) vs. Cori’s (III) enzyme defect

ABCD
Anderson’s=Branching enzyme.

Cori’s=Debranching enzyme.

Also see: Glycogen Storage diseases.

Metallo-enzymes

Metals and corresponding enzymes is one of the frequently  asked questions in MCQ exams.

Zinc

  1. Carbonic anhydrase
  2. Dehydrogenases(LDH,Alcohol dehydrogenase)
  3. Kinases
  4. Peptidases

Magnesium

  1. Hexokinase
  2. Enolase

Copper

  1. Tyrosinase
  2. Cytochrome Oxidase

Iron

  1. Cytochrome oxidase
  2. Catalase
  3. Peroxidase

Molybdenum

  1. Xanthine oxidase

Manganese

  1. Superoxide dismutase

Calcium

  1. Lecithinase
  2. Lipase

Co Factors of enzymes

Glutathion peroxidase- selinium
carbonic anhydrase- zinc
tyrosinase- copper
cytochrome oxidase- copper
xanthine oxidase- Mo
Superoxidase dismutase- Mn
Dehydrogenases- Zn
Kinases & peptidases- Mg
KG dehydrogenases- TPP

carboxylation – Biotin
transamination – Pyridoxin

Rate Limiting steps in biochemical reactions.

Rate limiting steps in various biochemical reactions taking place inside cells is of vital importance while formulating drugs to fight specific diseases affecting these reactions. So these rate limiting steps are frequently asked in various entrance exams.
Glycolysis – Phosphofructokinase
Glycogen synthesis - Glycogen synthetase
Glycogenolysis - Glycogen Phosphorylase
Gluconeogenesis – Phosphoenolepyruvate; Fructose 1,6 biphosphatase
TCA cycle- Isocitrate dehydrogenase
Cholesterol synthesis- HMG CoA Reductase
Bile acid synthesis – 7 alpha hydroxylase
Fatty acid synthesis - acetyl CoA carboxylase

Ketone body synthesis -HMG CoA synthetase
Uric acid synthesis - Xanthine Oxidase
Norepinephrine(catecholamine) synthesis- Tyrosine hydroxylase
Tyrosine———–>DOPA(Tyrosine hydroxylase)
Acetylcholine synthesis- Uptake of choline
Urea synthesis – Carbamoyl transferase

 

Glucose transporters

Glucose enters cells by facilitated diffusion or by secondary active transport with Sodium(in intestine and kidneys)

Glucose transporters(Glut 1-7) are responsible for facilitated diffusion of glucose across cell membranes.

They differ from sodium dependant glucose transporters(SGLT1 and 2)

Glucose Transporters and their functions

GLUT-1

Basal glucose uptake

Present in brain,kidney,colon,placenta and erythrocytes.

GLUT 2

Beta cell glucose sensor

Transport glucose out of intestinal and renal epithelial cells

Beta cells of pancreas,liver,Small Intestine,Kidneys.

GLUT 3

Basal glucose uptake

Brain,placenta,Kidney

GLUT4

Insulin stimulated glucose uptake

Present in skeletal and cardiac muscle,adipose tissue.

GLUT 5

Fructose transport

Jejunum and sperm

Glut 6

Pseudogene

GLUT 7

Glucose 6 phosphate transporter in endoplasmic reticulum.

Liver

Na+ Glucose co-transporters

SGLT 1

Absorption of glucose from Small Intestine and renal tubules

SGLT 2

Absorption of glucose from renal tubules.

Important points

  1. Basal glucose uptake by- GLUT1 and GLUT3
  2. GLUT 2 is present in beta cells of pancreas, so it controls postprandial hyperglycemia
  3. GLUT4 is insulin dependent so no of GLUT4 decreases after overnight fasting.

Glycogen Storage diseases

Liver Glycogenoses

Disorders with hepatomegaly and hypoglycemia

  1. Type I-Von Gierke -Glucose 6 phosphatase
  2. Type III-Cori/Forbe limit dextrinosis- Debranching enzyme deficiency
  3. Type VI-Her’s Liver phosphorylase
  4. Type IX-Phosphorylase Kinase deficiency
  5. Type XI-Fancon/Bickel Glut 2 deficiency

With Liver cirrhosis

Type IV-Anderson’s -Branching enzyme deficiency

Muscle Glycogenoses

With muscle energy impairment

  1. Type V- Mc Ardle – muscle phosphorylase
  2. Type VII-Tarui-Phosphofructokinase deficiency

With progressive skeletal muscle myopathy/cardiomyopathy

Type II-Pompe’s Lysosomal acid Alpha glucosidase deficiency

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