Liver as a hub of cholesterol metabolism All nucleated cells have the capacity to synthesize cholesterol from acetyl-CoA (like most biological lipids). 90% of synthesis occurs in liver and intestine. The cholesterol biosynthesis pathway involves enzymes that are in the cytoplasm, microsomes (ER), and peroxisomes. Liver obtains cholesterol from 3…
Tag: Biochemistry
PGMEE, MRCS, USMLE, MBBS, MD/MS 
Lipoprotein Metabolism Simplified
Lipoproteins Composition of Lipoproteins: Non-polar core – mainly triglycerides and cholesteryl esters Single surface layer – amphipathic phospholipids and cholesterol Apoprotein or Apolipoprotein Class Abbreviation Density Protein Lipid content Electrophoretic mobility Chylomicrons CM lowest lowest highest (exogenous triacylglycerol) don’t migrate Very low density lipoproteins VLDL .. .. .. (endogenous triacylglycerol)…
PGMEE, MRCS, USMLE, MBBS, MD/MS 
Inheritance of Disease – Mnemonics
Lets work with some generalizations 1. X-linked dominant, mitochondrial and Y-linked conditions are rare. You need to remember them. 2. Usually inherited in autosomal dominant pattern are: Mostly mutations in non-enzymatic structural proteins (e.g. collagen, fibrillin, cytoskeletal proteins of RBC) or in membrane receptors (e.g. LDL receptor) Diseases due to diminished…
PGMEE, MRCS, USMLE, MBBS, MD/MS 
Polymerase Chain Reaction (PCR) Made Easy
What is Polymerase Chain Reaction ? It is a process of artificial DNA replication (amplification of a selected part of DNA). As the name suggests: Polymerase: It requires DNA polymerase for extending the added primers to complete DNA replication. Chain Reaction: PCR is run in cycles. The number of molecules…
PGMEE, MRCS, USMLE, MBBS, MD/MS 
Amino Acids Mnemonics
What are amino acids ? Amino acids are molecules containing: An amine group A carboxylic acid group A side chain that varies between different amino acids Assign the names of these amino acids to 20 different alphabets The technique that you are going to use to remember all these are given…
PGMEE, MRCS, USMLE, MBBS, MD/MS 
Cell Cycle Made Easy
Stages of Cell Cycle Interphase Mnemonic: Go Sally Go! Make Children 1. G1 phase 2. S phase 3. G2 phase 4. Mitosis 5. Cytokinesis 1. G1 (Gap 1) phase: Early and late phase divided by Restriction (R) point Functions: Preparation for DNA replication (synthesis of replication proteins cyclin D) Thymidine…
PGMEE, MRCS, USMLE, MBBS, MD/MS 
Urea Cycle and Defects with Mnemonics
Mnemonic for Urea Cycle Intermediates Orange Cola, Coffee, Alcohol of Argentina For Aggressive Urine Orange: Ornithine Cola: Carbamoyl Phosphate Coffee: Citrulline Alcohol: Aspartate (enters cycle) Argentina: Arginosuccinate For: Fumarate (leaves cycle) Aggressive: Arginine Urine: Urea (leaves cycle) Structure of Urea NH2-CO-NH2 (1 amide from aspartate and 1 from ammonia) Amide…
PGMEE, MRCS, USMLE, MBBS, MD/MS 
Electron Transport Chain (ETC) and Oxidative Phosphorylation : Mnemonic
General concepts of ETC and Oxidative Phosphorylation: 1. Occurs in cell cytosol: Glycolysis 2. Occurs in mytochondrial matrix: Kreb’s (TCA) cycle 3. Occurs in mitochondrial inner membrane: ETC – Stepwise movement of electrons from high energy to low energy that activates proton pump which transports proton from the mitochondrial matrix to mitochondrial inter-membrane and…