PLTW Principles of Biomedical Science - Ultimate Exam Prep Guide

Crime Scene Evidence & Analysis
- Key Evidence Types: hair, fingerprints, blood spatter, saliva, DNA
Medical Examiner Role: Determines manner, cause, and mechanism of death
- Manner: Natural vs. unnatural (homicide, suicide, accident)
- Cause: Specific reason (stroke, gunshot wound)
- Mechanism: How body died (exsanguination, asphyxiation)
- Time of Death:
  - Glaister Equation: $(98.6°F - body temp) ÷ 1.5 = hours since death$

DNA Structure:
- Nucleotide components: Phosphate group, deoxyribose sugar, nitrogenous base
- Base pairs: A-T, G-C (Chargaff's rule)
- Purines: Adenine, Guanine (double ring)
- Pyrimidines: Cytosine, Thymine (single ring)
- RNA difference: Uses Uracil instead of Thymine instead of Thymine
DNA Analysis Techniques:
- Restriction Enzymes: Cut DNA at specific sequences (e.g., HaeIII cuts at GG-CC)
- Gel Electrophoresis: Separates DNA fragments by size (moves negative → positive)
- RFLPs: Restriction Fragment Length Polymorphisms - different length fragments created by restriction enzymes
- PCR: Polymerase Chain Reaction - creates millions of copies from small DNA sample

Presumptive Tests: LCV, Luminol, Kastle Meyer (suggest presence of blood)
Confirmatory Tests: Verify substance is blood
Blood Components:
- RBCs (Erythrocytes): Oxygen transport, contain hemoglobin
- WBCs (Leukocytes): Immune response
- Platelets (Thrombocytes): Blood clotting
- Plasma: Liquid portion carrying nutrients, hormones, waste
- Hemoglobin: Oxygen-binding protein in RBCs
- Hematocrit: Proportion of RBCs to total blood volume
Blood Types
- Universal donor: O negative
- Universal recipient: AB positive (no anti-A or anti-B antibodies)
- Type O: No agglutination with anti-A or anti-B

Feature	Type 1	Type 2
Cause	Autoimmune destruction of beta cells	Insulin resistance/receptor problems
Insulin Production	Little to none	Often excess (compensation)
Treatment	Insulin injections/pump, diet, exercise	Weight loss, exercise, oral medication, diet
Onset	Often before adulthood	Usually middle-aged adults
Risk Factors	Genetic	Overweight, genetic, certain populations

Key Testing & Symptoms
- A1C Test: Gold standard - measures average glucose over 3 months
- Glucose Tolerance Test: Shows how body processes glucose
- Symptoms: Fatigue, dizziness, excessive thirst and urination
- Complications: Nerve damage (nervous system), Kidney damage (urinary system), Heart disease (cardiovascular)

Feedback Mechanisms:
- Negative feedback: Returns system to normal (most body systems)
- Positive feedback: Amplifies response (blood clotting, childbirth)
Osmosis: Movement of water from high to low concentration
- Explains diabetic dehydration: high blood sugar draws water from tissues
Cell Environment Types:
- Isotonic: Equal concentration inside/outside cell
- Hypotonic: Lower concentration outside cell (water enters)
- Hypertonic: Higher concentration outside cell (water leaves)

Protein Synthesis Process:
- DNA → mRNA (transcription in nucleus) → protein (translation at ribosomes)
- Remember: TransCription before TransLation (C comes before L)
Codon Chart: Memorize common start (AUG = Methionine) and stop codons (UAA, UAG, UGA)
Cell Division
- Mitosis: Creates identical body cells (46 chromosomes)
- Meiosis: Creates sex cells/gametes (23 chromosomes)

Dominant: Expressed when present (one copy sufficient)
Recessive: Only expressed with two copies
Pedigree Analysis: Square = male, Circle = female; Shaded = affected
Punnett Squares: Predict offspring genotypes/phenotypes
Genetic Disorders
- Sickle Cell: Recessive hemoglobinopathy causing sickle-shaped RBCs
- Familial Hypercholesterolemia: Dominant disorder with LDLR gene mutation affecting LDL clearance

Anatomy & Blood Flow
- Path of Blood Flow: Body → Superior/Inferior Vena Cava → Right Atrium → Tricuspid Valve → Right Ventricle → Pulmonary Artery → Lungs → Pulmonary Veins → Left Atrium → Bicuspid/Mitral Valve → Left Ventricle → Aortic Valve → Aorta → Body
- Heart Valves: Prevent backflow of blood
- Mitral Valve Prolapse: Incomplete closure causing regurgitation
Heart Electrical System
- SA Node: "Pacemaker" (top of right atrium)
- AV Node: Bottom of right atrium near septum
- Conduction Pathway: SA → AV → Bundle branches → Purkinje fibers
- EKG Components:
  - P wave: Atrial depolarization (contraction)
  - QRS complex: Ventricular depolarization (contraction)
  - T wave: Ventricular repolarization (relaxation)
- Normal Heart Rate: 60-100 bpm

Blood Pressure:
- Normal: 90-120/60-80 mmHg
- Measured with: Sphygmomanometer
Cholesterol:
- LDL ("bad"): <100 mg/dL ideal, <130 acceptable
- HDL ("good"): >40 mg/dL, >60 "heart protective"
Atherosclerosis: Fatty buildup in arteries increasing blood pressure
Treatment Options:
- CABG (bypass): Most invasive, requires open heart surgery
- Stents: Metal structures to hold arteries open
- Angioplasty: Balloon to expand arteries

Pathogen Types
- Living: Bacteria, Fungi, Helminths (worms), Protists
- Non-living: Viruses, Prions
Disease Transmission
- Routes: Airborne, contact, droplets, food/water, vectors
- Prevention: Hand washing, vaccination, isolation, disinfection
Immune System Defenses
- First Line (Non-specific): Skin, mucus, hairs/cilia, inflammation
- Second Line (Non-specific): White blood cells, phagocytes
- Third Line (Specific): T-cells, B-cells, antibodies
Bacteria Identification
- Gram Staining:
  - Crystal violet → all bacteria stain purple
  - Iodine → fixes stain
  - Alcohol wash → removes stain from gram-negative
  - Safranin → stains gram-negative pink/red
- Gram-positive: Thick peptidoglycan layer (stains purple)
- Gram-negative: Thin peptidoglycan layer (stains pink)
Culture Techniques
- Proper PPE: Essential for safety
- Streak Plate Method: Allows isolation of colonies
- Aseptic Technique: Prevent contamination

HIPAA Health Information Portability and Accountability Act
- Primary purpose: Protect patient confidentiality
- Exceptions: Law enforcement, public health concerns, extreme emergencies

Time of Death: $(98.6°F - body temp) ÷ 1.5 = hours since death$
Heart Rate from EKG: (# \text{ of beats in 6 seconds}) × 10 = \text{beats per minute}
Remember: For multiple choice questions, eliminate obviously wrong answers first, then carefully consider remaining options. For open-ended questions, organize your thoughts with bullet points before writing full responses.