MRCOG Part 1: Biochemistry - Essential Study Guide

This is your essential guide to the Biochemistry section of the MRCOG Part 1 exam. We built it from our own experience of sitting the exam, the RCOG syllabus and the official reading list. It lists the biochemistry concepts most often tested, section by section.

Why Biochemistry matters in MRCOG Part 1

Biochemistry is crucial for understanding the molecular mechanisms underlying physiological processes in the human body, particularly in the context of obstetrics and gynaecology. For the MRCOG Part 1 exam, a strong grasp of biochemical principles is necessary to understand metabolism, hormone action, cell signalling, and the molecular basis of various diseases.

Biochemistry syllabus, section by section

ICell and Molecular Biology

Cellular Structure and Function

Organelles
  • Structure and function of nucleus, endoplasmic reticulum (rough and smooth), Golgi complex, mitochondria, lysosomes, peroxisomes
  • Role of ribosomes in protein synthesis
Plasma Membrane
  • Composition and function of the phospholipid bilayer
  • Role of membrane proteins (transporters, receptors)
  • Transport of molecules across the membrane
Cytoskeleton
  • Composition and function of microtubules, microfilaments, and intermediate filaments
  • Role in cell shape, movement, and intracellular transport

Cell Signaling

Types of Signaling
  • Endocrine, paracrine, autocrine
  • Signalling via membrane-attached proteins
  • Role of hormones and growth factors
Signal Transduction Pathways
  • Role of second messengers (cAMP, cGMP, IP3, Ca2+, diacylglycerol)
  • Activation of protein kinases (e.g., protein kinase C)
  • G-protein coupled receptors
  • MAP kinase pathway
  • Phospholipase C pathway
Eicosanoids
  • Synthesis and major groups: prostaglandins, prostacyclins, thromboxanes, leukotrienes

Cell-Cell Adhesion and Communication

Cell Adhesion Molecules
  • Cadherins, integrins, selectins, immunoglobulin-like molecules
  • Role in cell-cell and cell-matrix interactions
Cell Junctions
  • Tight junctions, adherens junctions, desmosomes, hemidesmosomes, gap junctions
  • Role in tissue integrity and intercellular communication
  • Role of gap junctions in myometrial contractility

Cell Cycle and Cancer

Cell Cycle
  • Phases of the cell cycle (G1, S, G2, M)
  • Role of cyclins and cyclin-dependent kinases (CDKs)
  • Cell cycle checkpoints (DNA damage, spindle)
Oncogenes and Tumor Suppressors
  • Role of proto-oncogenes and oncogenes in cancer development
  • Function of tumor suppressor genes (e.g., p53, APC)
  • Mechanisms of tumorigenesis

DNA, RNA and Protein Synthesis

DNA Structure and Replication
  • Base pairing rules (adenine-thymine, cytosine-guanine)
  • Process of DNA replication (leading and lagging strands, Okazaki fragments, DNA polymerase, helicase, DNA ligase)
RNA Synthesis and Processing
  • Process of transcription (RNA polymerase)
  • Role of mRNA, tRNA, and rRNA
  • Gene splicing (exons and introns)
Protein Synthesis
  • Process of translation (ribosomes, codons, anticodons)
  • Post-translational modifications

Laboratory Techniques

Molecular Biology Techniques
  • Southern blotting, Northern blotting, Western blotting
  • Polymerase chain reaction (PCR)
  • DNA microarrays

IISteroids and Prostaglandins

Steroid Hormones

Synthesis and Metabolism
  • Role of cholesterol as a precursor
  • Key enzymes in steroidogenesis (CYP enzymes, HSD enzymes)
  • Tissue-specific patterns of steroidogenesis (adrenal cortex, gonads, placenta)
  • Metabolism and clearance of steroid hormones
Mechanism of Action
  • Intracellular receptors
  • Genomic and non-genomic actions
  • Regulation of gene transcription
Classification and Examples
  • Mineralocorticoids (aldosterone)
  • Glucocorticoids (cortisol)
  • Androgens (testosterone, DHEA)
  • Estrogens (estradiol)
  • Progestogens (progesterone)

Prostaglandins

Synthesis and Metabolism
  • Role of arachidonic acid as a precursor
  • Cyclooxygenase (COX) enzymes (COX-1, COX-2)
  • Prostaglandin synthase enzymes
  • Metabolism by 15-hydroxyprostaglandin dehydrogenase
Mechanism of Action
  • G-protein-coupled receptors
  • Signal transduction pathways (cAMP, Ca2+)
  • Cellular effects
Physiological Roles
  • Regulation of myometrial contractility
  • Role in inflammation and pain
  • Effects on blood vessels

Regulation of Myometrial Contractility

Contractant Molecules
  • Oxytocin
  • Prostaglandin F2α
  • Mechanism of action on myometrial cells
Relaxant Molecules
  • Progesterone
  • Nitric oxide
  • Relaxin
  • Prostacyclin
  • Mechanism of action on myometrial cells

IIIFluid and Acid-Base Balance

Fluid and Electrolyte Balance

Fluid Compartments
  • Intracellular and extracellular fluid volumes
  • Changes in fluid distribution during pregnancy
Electrolyte Balance
  • Regulation of sodium, potassium, calcium, and phosphate levels
  • Role of aldosterone, PTH, and vitamin D

Acid-Base Balance

Definitions
  • Acids, bases, pH
  • Acidosis, alkalosis, acidaemia, alkalaemia
Buffer Systems
  • Bicarbonate buffer system
  • Hemoglobin as a buffer
  • Role of the kidneys and lungs in acid-base regulation
Acid-Base Disturbances
  • Respiratory acidosis and alkalosis
  • Metabolic acidosis and alkalosis
  • Interpretation of blood gas results
  • Compensation mechanisms
Acid-Base Balance in Pregnancy
  • Physiological respiratory alkalosis
  • Effects of hyperventilation during labor
  • Fetal acid-base abnormalities

IVCalcium Homeostasis and Bones

Calcium Homeostasis

Regulation of Serum Calcium
  • Role of parathyroid hormone (PTH)
  • Role of vitamin D (calcitriol)
  • Role of calcitonin
  • Calcium-sensing receptor (CaSR)
Calcium Absorption and Excretion
  • Intestinal absorption (transcellular and paracellular pathways)
  • Renal reabsorption
  • Factors affecting calcium balance

Bone Metabolism

Bone Structure
  • Types of bone tissue (trabecular, cortical)
  • Bone matrix (osteoid, hydroxyapatite)
  • Bone cells (osteoblasts, osteoclasts, osteocytes)
Bone Remodeling
  • Process of bone resorption and formation
  • Regulation by hormones (PTH, vitamin D, calcitonin, estrogen)
  • Role of RANKL, RANK, and OPG
Osteoporosis and Osteopenia
  • Definition and diagnosis
  • Risk factors and causes
  • Biochemical measures of bone turnover
  • Management and prevention

Phosphate Homeostasis

Regulation of Phosphate
  • Role of PTH and vitamin D
  • Fibroblast growth factor 23 (FGF23)

Pregnancy and Calcium Balance

Maternal Adaptations
  • Changes in calcium absorption and excretion
  • Alterations in bone mineral density
  • Role of PTHrP
Fetal Calcium Requirements
  • Placental calcium transport

VHuman Metabolism: Carbohydrates, Fats, and Proteins

Carbohydrate Metabolism

Forms of Carbohydrate
  • Monosaccharides, disaccharides, polysaccharides
  • Dietary sources of carbohydrates
Glycolysis
  • Anaerobic pathway for glucose metabolism
  • Production of pyruvate and lactate
  • Net ATP yield
  • Regulation of glycolysis
Aerobic Respiration
  • Pyruvate dehydrogenase (PDH) reaction
  • Tricarboxylic acid (TCA) cycle
  • Electron transport chain
  • ATP yield from glucose oxidation
Gluconeogenesis
  • Synthesis of glucose from non-carbohydrate precursors
  • Role of the liver in gluconeogenesis
Glycogen Metabolism
  • Glycogen synthesis and breakdown
  • Role of liver and muscle glycogen
Carbohydrate Metabolism During Starvation
  • Depletion of glycogen stores
  • Activation of gluconeogenesis
  • Role of muscle protein breakdown

Fat Metabolism

Forms and Functions of Fats
  • Triacylglycerols (TAGs), phospholipids, cholesterol
  • Roles in energy storage, membrane structure, hormone synthesis
Lipolysis
  • Mobilization of fatty acids from TAGs
  • Role of hormone-sensitive lipase (HSL)
  • Regulation by insulin, glucagon, and adrenaline
Transport of Fats
  • Lipoproteins (chylomicrons, VLDL, LDL, HDL)
  • Role of albumin in fatty acid transport
Beta-Oxidation
  • Oxidation of fatty acids in mitochondria
  • Production of acetyl CoA, NADH, and FADH2
  • ATP yield from fatty acid oxidation
Ketogenesis
  • Synthesis of ketone bodies (acetoacetate, D-3-hydroxybutyrate) in the liver
  • Role of ketone bodies during starvation
  • Regulation of ketogenesis

Protein Metabolism

Amino Acid Degradation
  • Transamination and deamination reactions
  • Role of glutamate dehydrogenase
Urea Cycle
  • Detoxification of ammonia
  • Synthesis of urea in the liver
Fate of Carbon Skeletons
  • Glucogenic and ketogenic amino acids
  • Intermediates of the TCA cycle and gluconeogenic pathway

Metabolic Adaptations

Metabolism in the Maternal-Fetal Unit
  • Maternal insulin resistance
  • Fetal glucose utilization
Metabolism in the Newborn Baby
  • Activation of gluconeogenesis and lipolysis
  • Role of brown adipose tissue in thermogenesis

Inborn Errors of Metabolism

Phenylketonuria
  • Defect in phenylalanine hydroxylase
  • Consequences of phenylalanine accumulation
  • Importance of early diagnosis and dietary management
Other Inborn Errors
  • Disorders affecting urea cycle
  • Disorders affecting amino acid metabolism

Diabetes Mellitus

Diabetic Ketoacidosis
  • Uncontrolled lipolysis and ketogenesis
  • Metabolic acidosis and its consequences
  • Management of diabetic ketoacidosis
Gestational Diabetes Mellitus
  • Insulin resistance during pregnancy
  • Impact on fetal growth and development

How to master Biochemistry

  • Review: work through each section systematically and understand the core concepts before moving on.
  • Active learning: draw diagrams, build mind maps and explain concepts to someone else.
  • Test yourself: try our free practice questions, then work through the biochemistry questions in the Uterio question bank.

Additional resources