GEM / MSCAA Module 1 Reworked Notes Foundation: Structure, Function and Defence

Master summary flashcards covering cell biology, tissues, genetics, immunology, microbiology, and pharmacology basics for MSCAA Module 1.

What is the core chain used to reduce difficult topics in Module 1?

Structure -> function -> mechanism -> clinical consequence -> test or treatment.

What is the clinical definition of homeostasis?

Keeping the internal environment within a narrow range despite external change.

What anatomical plane divides the body into left and right?

Sagittal plane.

Which ribs are classified as 'true ribs' and why?

Ribs 1-7, because they attach directly to the sternum through costal cartilage.

Why does the parietal pleura cause sharp chest pain when inflamed?

Because the parietal pleura is pain-sensitive, whereas the visceral pleura is not.

What are the four basic tissue types in the body?

Epithelial, connective, muscle, and nervous tissue.

What is the term for epithelium that has no direct blood supply and is nourished by diffusion?

Avascular.

Which type of epithelium acts as a thin diffusion barrier for gas exchange in the alveoli?

Simple squamous epithelium.

Where is pseudostratified ciliated columnar epithelium primarily found?

The respiratory tract.

What is the function of 'umbrella cells' in transitional epithelium (urothelium)?

They flatten as the bladder fills to provide a stretch and urine barrier.

How do cilia differ from microvilli in function?

Cilia are motile projections that move material (like mucus), whereas microvilli are non-motile and increase surface area for absorption.

What are the components of the basement membrane?

Type IV collagen, glycoproteins (such as laminin), and proteoglycans/glycosaminoglycans.

What acronym is used to remember cell adhesion molecules?

SAMMI (Selectins, Cadherins, Ig superfamily, Mucins, Integrins).

Which cell junction type is targeted in the disease Pemphigus vulgaris?

Desmosomes.

What is the functional difference between a desmosome and a hemidesmosome?

Desmosomes connect cells to other cells; hemidesmosomes anchor basal epithelial cells to the basement membrane.

What is the purpose of gap junctions in cardiac muscle?

They allow small ions and molecules to pass directly between cells for electrical coupling.

What prevents the free passage of charged or polar substances across the plasma membrane?

The hydrophobic core of the phospholipid bilayer.

How many sodium and potassium ions does the Sodium-potassium ATPase move?

It moves 3 sodium ions ($Na^+$) out and 2 potassium ions ($K^+$) in using ATP.

What is the specific mechanism used by glucose to enter cells via GLUT transporters?

Facilitated diffusion.

What characterizes 'secondary active transport'?

It uses an ion gradient created by primary active transport rather than using ATP directly.

What is the difference between paracrine and autocrine signaling?

Paracrine signals act locally on nearby cells; autocrine signals act on the same cell that released them.

Which type of ligand typically binds to intracellular/nuclear receptors?

Lipophilic ligands, such as steroid hormones, thyroid hormone, and vitamin D.

What is the function of second messengers like cAMP and $IP_{3}$?

They amplify intracellular signals from a receptor to produce a large cellular response.

What is the difference between anabolic and catabolic reactions?

Anabolic reactions build larger molecules and require energy; catabolic reactions break molecules down and release energy.

Which vitamins are fat-soluble?

Vitamins A, D, E, and K.

What is the clinical role of Vitamin K?

It is needed for gamma-carboxylation of clotting factors II, VII, IX, and X, plus proteins C and S.

How do competitive inhibitors affect enzyme kinetics?

They increase $K_m$ (reduce apparent affinity) but leave $V_{max}$ unchanged.

How do non-competitive inhibitors affect enzyme kinetics?

They decrease $V_{max}$ but leave $K_m$ unchanged.

What defines the primary structure of a protein?

The amino acid sequence.

What are the base-pairing rules for DNA?

A-T (Adenine-Thymine) and C-G (Cytosine-Guanine).

What is the difference between a missense mutation and a nonsense mutation?

A missense mutation changes one amino acid; a nonsense mutation changes a codon into a stop codon, resulting in a truncated protein.

What is the inheritance risk for an autosomal recessive condition if both parents are carriers?

25% affected, 50% carrier, and 25% unaffected non-carrier for each pregnancy.

Classic Phenylketonuria (PKU) is caused by a deficiency in which enzyme?

Phenylalanine hydroxylase.

What is the clinical consequence of untreated PKU?

Intellectual disability, seizures, musty/mousy odour, and fairer skin/hair.

Which pathway is defective in Familial Hypercholesterolaemia (FH)?

The LDL receptor pathway.

What are tendon xanthomas?

Highly specific cholesterol deposits in tendons (like the Achilles) often seen in Familial Hypercholesterolaemia.

What occurs during the S phase of the cell cycle?

DNA replication.

What are the three germ layers created during gastrulation?

Ectoderm, mesoderm, and endoderm.

What are the major derivatives of the endoderm?

Epithelial lining of the gut and respiratory tract, liver, pancreas, and thyroid follicular cells.

What is the difference between serum and plasma?

Serum is plasma after clotting factors have been removed.

What is the average lifespan of a Red Blood Cell (erythrocyte)?

Approximately 120 days.

Which white blood cell is most associated with acute bacterial infection and phagocytosis?

Neutrophils.

Define 'metaplasia'.

The replacement of one differentiated cell type by another better suited to stress (e.g., squamous metaplasia in the bronchi of smokers).

What is the difference between hypertrophy and hyperplasia?

Hypertrophy is an increase in cell size; hyperplasia is an increase in cell number.

Which type of necrosis is characteristic of ischaemic infarction in solid organs (except the brain)?

Coagulative necrosis.

What is the hallmark of liquefactive necrosis?

Tissue is digested into liquid, typically seen in brain infarcts or abscesses.

Define 'apoptosis'.

Programmed cell death that occurs without major inflammation, characterized by cell shrinkage and chromatin condensation.

What is the purpose of PAMPs and DAMPs in the immune response?

PAMPs (pathogen-associated) and DAMPs (damage-associated) are patterns detected by pattern recognition receptors to trigger innate immunity.

What is the difference between exudate and transudate?

Exudate is protein-rich inflammatory fluid; transudate is low-protein fluid caused by hydrostatic or oncotic pressure imbalances.

What are the steps of leukocyte recruitment during inflammation?

Margination -> Rolling -> Firm adhesion -> Diapedesis/transmigration -> Chemotaxis.

What are the roles of C3a and C5a in the complement system?

They act as anaphylatoxins to promote inflammation and mast cell degranulation; C5a is also a neutrophil chemoattractant.

Which antibody class is the first to appear in a primary immune response?

IgM.

Which antibody class is responsible for mucosal immunity and is found in saliva and breast milk?

IgA.

What is the mechanism of Type I Hypersensitivity?

IgE-mediated mast cell degranulation, seen in anaphylaxis and allergies.

Where does the thoracic duct drain into the venous system?

The left venous angle.

What is the structural difference between continuous, fenestrated, and sinusoidal capillaries?

Continuous have a solid lining; fenestrated have pores; sinusoidal have large gaps in the endothelium and basement membrane.

What is the main component of the Gram-negative bacterial outer membrane that acts as an endotoxin?

Lipopolysaccharide (LPS).

Which antibiotic class inhibits bacterial DNA replication by targeting DNA gyrase?

Fluoroquinolones (e.g., ciprofloxacin).

What is a specific side effect/caution associated with gentamicin?

Nephrotoxicity and ototoxicity.

Why are enveloped viruses more vulnerable to alcohol and soap than non-enveloped viruses?

Disrupting the host-derived lipid envelope removes their ability to infect cells.

How do retroviruses like HIV persist in the host?

They use reverse transcriptase to create DNA that integrates into the host genome as a provirus.

What is the latent site for the Varicella-zoster virus (VZV)?

Dorsal root or cranial nerve sensory ganglia.

Why does shingles (Herpes zoster) present in a dermatomal pattern?

Because the virus reactivates in a single sensory ganglion and travels down the corresponding sensory nerve to the skin.

What is the difference between pharmacodynamics and pharmacokinetics?

Pharmacodynamics is what the drug does to the body; pharmacokinetics is what the body does to the drug (ADME).

What does 'efficacy' mean in pharmacology?

The maximum effect a drug can produce.

What is the mechanism of action for local anaesthetics?

They block voltage-gated sodium channels ($Na^+$), preventing signal propagation.

Which autonomic receptor is responsible for slowing the heart rate?

Muscarinic $M_2$ receptors.

What are the effects of sympathetic stimulation on the bronchi?

Bronchodilation via $\beta_2$ adrenergic receptors.

In diagnostic testing, what does 'SnNout' stand for?

Sensitive test Negative rules out (high sensitivity).

What is lead-time bias in screening?

Diagnosis appears earlier, making survival look longer even if the time of death is unchanged.

How do NSAIDs like ibuprofen cause gastric ulcers mechanistically?

By inhibiting COX enzymes, they reduce protective prostaglandins in the stomach lining.

What connects the actin cytoskeleton between neighbouring cells?

Adherens junctions.

Which complement product forms the membrane attack complex (MAC)?

C5b-9.

What is the primary function of albumin?

Maintains intravascular oncotic pressure and carries molecules like bilirubin and hormones.