United States Medicine and Disease Olympiad (USMDO) Comprehensive Curriculum and Examination Study Guide

Study Guide: Cell Biology, Human Physiology, and Human Disease

Cell Biology & Genetics
1. Macromolecules

Types of Macromolecules: Macromolecules are large complex molecules that are fundamental to biological processes. They can be categorized into four main types:

Carbohydrates

Serve as energy sources and structural components.

  • Monosaccharides (e.g., glucose, fructose)

  • Disaccharides (e.g., sucrose, lactose)

  • Polysaccharides (e.g., starch, cellulose)  


    Figure: Structures of monosaccharides, disaccharides, and polysaccharides

Proteins

Composed of amino acids and perform various functions in the cell, including:

  • Enzymatic activity

  • Structural support

  • Signaling

Nucleic Acids

DNA and RNA are vital for storing and transmitting genetic information.

  • DNA: Deoxyribonucleic acid, contains the genetic blueprint.

  • RNA: Ribonucleic acid, involved in protein synthesis.

Lipids

Insoluble in water and include fats, oils, and phospholipids, which form cell membranes.   


Figure: Structures of triglycerides, phospholipids, and cholesterol

2. Structures of the Cell

A cell is the basic unit of life, and its structure is directly related to its function. Key components include:

  • Nucleus: Contains DNA, surrounded by a double membrane called the nuclear envelope.

  • Mitochondria: The powerhouse of the cell where ATP is produced through cellular respiration.

  • Endoplasmic Reticulum (ER): There are two types:

    • Rough ER: Has ribosomes and is involved in protein synthesis.

    • Smooth ER: Lacks ribosomes; synthesizes lipids and detoxifies certain chemicals.

  • Golgi Apparatus: Modifies, packages, and distributes proteins and lipids.

  • Ribosomes: Protein synthesis occurs here, can be free in the cytosol or bound to the rough ER.


Figure: Overview of cell structures and their functions

3. Cell Membrane

The cell membrane acts as a barrier that separates the interior of the cell from the external environment. Its structure comprises:

  1. Phospholipid Bilayer: Composed of hydrophilic heads and hydrophobic tails, creating a semi-permeable membrane.

    • Fluid Mosaic Model: Membrane proteins float in or on the fluid lipid bilayer like boats on a lake.

   


  Figure: Fluid mosaic model of the cell membrane

  1. Proteins: Integral and peripheral proteins perform various functions (e.g., transport, signaling).

  2. Carbohydrates: Used for cell recognition and signaling, often attached to proteins (glycoproteins) or lipids (glycolipids).

4. Transport Mechanisms

Passive Transport

This process doesn't require energy (ATP) when substances move down their concentration gradient.

  • Diffusion: Movement from high to low concentration (e.g., oxygen, carbon dioxide).

  • Osmosis: Diffusion of water across a selectively permeable membrane.

Active Transport

Requires energy to move substances against their concentration gradient:

  • Sodium-Potassium Pump: Pumps sodium ions out and potassium ions into the cell, crucial for maintaining cell potential.

   


  Figure: Passive vs. Active transport mechanisms

5. Cellular Respiration

The process of converting glucose into energy (ATP).

  1. Glycolysis:

    • Location: Cytoplasm

    • Breakdown of glucose → 2 molecules of pyruvate + 2 ATP (and NADH).

  2. Krebs Cycle (Citric Acid Cycle):

    • Location: Mitochondrial matrix

    • Converts acetyl-CoA into CO₂ and produces NADH and FADH₂.

  3. Electron Transport Chain:

    • Location: Inner mitochondrial membrane

    • Uses NADH and FADH₂ to produce ATP through oxidative phosphorylation.  


        Figure: Overview of cellular respiration stages

Human Physiology
1. Homeostasis

Homeostasis refers to the regulation of internal conditions (e.g., temperature, pH) to maintain life. Negative feedback loops are a key mechanism:

  • Example: Blood glucose regulation—insulin decreases blood glucose levels, while glucagon increases it.


Figure: Mechanism of homeostatic regulation

2. The Circulatory System

The circulatory system pumps blood to and from all areas of the body.

  • Heart: Four chambers (two atria and two ventricles) that pump blood.

  • Blood Vessels: Arteries (carry blood away), veins (carry blood towards).

  • Components of Blood: Red blood cells (O₂ transport), white blood cells (immune defense), platelets (clotting).

   


  Figure: Major components of the circulatory system

3. The Respiratory System

The respiratory system's primary function is gas exchange. Key components include:

  • Nasal Cavity: Filters, warms, and humidifies air.

  • Trachea and Bronchi: Air passageways leading to lungs.

  • Alveoli: Tiny air sacs where gas exchange occurs (O₂ in, CO₂ out).


Figure: Structure of the respiratory system

4. The Immune System

The immune system protects against pathogens. It includes:

  • Innate Immunity: Immediate and non-specific responses (e.g., skin barriers, white blood cells).

  • Adaptive Immunity: Specific targeting of invaders, involves memory cells.


Figure: Overview of immune system components and functions

5. Common Human Diseases

We can explore specific examples of diseases and their impacts on various systems:

  1. Cancer: Uncontrolled cell division; types include leukemia (blood cancer) and carcinoma (tumors in organs).

  2. Diabetes: A metabolic disorder characterized by high blood sugar due to insulin issues—Type 1 (autoimmune) vs. Type 2 (lifestyle related).

  3. Cardiovascular Diseases: Diseases affecting the heart and blood vessels, often caused by atherosclerosis (build-up of plaques).

  4. Respiratory Diseases: Conditions such as asthma (airway inflammation) and COPD (progressive lung disease).

  5. Infectious Diseases: Caused by pathogens, e.g., HIV (virus affecting immune system) and tuberculosis (bacterial infection).


Figure: Overview of common diseases and affected systems