PLTW Principles of Biomedical Science End of Course Review Notes

Crime Scene Evidence and Death Investigation

• Obtaining Evidence at a Crime Scene (1.1.1): Five primary pieces of evidence that may be obtained from a crime scene to assist in solving a crime include:     * Hair.     * Fingerprints.     * Blood spatter patterns.     * Saliva.     * Digital evidence.     * DNA.

• Roles of a Medical Examiner (1.2.1): When performing an autopsy, the medical examiner looks for evidence regarding how a person died. This includes:     * Determining the manner, cause, and mechanism of death.     * Analyzing toxicology in blood and urine.     * Identifying evidence of disease.     * Identifying evidence of injury.

• Differentiating Manner, Cause, and Mechanism of Death (1.2.1):     * Manner of Death: The overarching reason a person died, categorized broadly as natural or unnatural.     * Cause of Death: The specific reason for death, such as a stroke, cardiac arrest, or a gunshot wound.     * Mechanism of Death: The specific physiological way the body died, such as exsanguination (bleeding out), asphyxiation (deprivation of oxygen), or lack of blood flow to the brain.

• Calculating Time of Death (1.2.2): Time of death can be estimated using the Glaister equation based on body temperature. For a body found at $8:00\,\text{A.M.}$ with a rectal temperature of $95.2\,^{\circ}\text{F}$:     * Equation: $\frac{98.4 - 95.2}{1.5} = 2.13\,\text{hours since death}$     * Estimation: The death occurred approximately $2\,\text{hours}$ prior, around $6:00\,\text{A.M.}$

DNA Structure, Function, and Analysis

• Nucleotide Structure (1.1.5): A nucleotide consists of three main parts:     * Phosphate group: Carries a negative charge, giving the overall DNA molecule a slightly negative charge.     * Nitrogenous base: Can be one of four types.     * Deoxyribose sugar: The five-carbon sugar found in DNA.

• DNA Bases and Structure (1.1.5):     * Purines: Adenine ($A$) and Guanine ($G$). These possess a double-ring structure.     * Pyrimidines: Cytosine ($C$) and Thymine ($T$). These possess a single-ring structure.     * Chargaff’s Rule: Complementary base pairing occurs as $A-T$ and $G-C$.     * Genetic Variation: DNA differs from person to person based on the specific sequence of these base pairs.

• RNA Comparison (1.1.5): In RNA, Thymine ($T$) is not present; it is replaced by the base Uracil ($U$).

• Complementary Strands (1.1.5): For a DNA strand with the sequence $GAATACGAT$, the binding strand is $CTTATGCTA$.

• Restriction Enzymes (1.1.5): Naturally produced by bacteria as a defense mechanism, these enzymes cut or digest DNA at particular sequences. For example, the enzyme HaeIII looks for the $GGCC$ pattern and cuts between the $GG$ and $CC$.

• Gel Electrophoresis (1.1.6): This process separates DNA molecules so they can be stained and visually analyzed.     * Purpose: To match a person to an unknown sample or view alleles in a genotype.     * DNA Migration: DNA runs from the negative end to the positive end because it is attracted to the positive side due to the negative charge of the phosphate groups.

• Restriction Fragment Length Polymorphism (1.1.6): RFLP refers to the differences in the lengths of DNA fragments created by digesting DNA with restriction enzymes. These fragments are run through gel electrophoresis to identify suspects or alleles.

• Polymerase Chain Reaction (1.1.5): PCR enables scientists to produce millions of copies of a specific DNA sequence from an originally small amount of DNA. It is used for research and diagnosing diseases or disorders.

• Using Enzymes for Genetic Diagnosis: Restriction enzymes can determine if a person has a mutation for a genetic disease, such as Familial Hypercholesterolemia ($FH$). In a gel electrophoresis test for $FH$:     * Lane 3: $Ff$     * Lane 4: $ff$     * Lane 5: $FF$     * Lane 6: $ff$     * Lane 7: $FF$     * Lane 8: $Ff$

Experimental Design

• Components of an Experiment (1.2.2): In an experiment testing a new drug to inhibit ovarian cancer cell growth where $1,000,000$ cells are grown in vitro and treated with varying concentrations:     * Independent Variable: The drug concentration.     * Dependent Variable: The number of dead cells counted after $24\,\text{hours}$.     * Control Group: The group with $0\,\%$ drug concentration added.

Hematology: Blood Components and Typing

• Testing for Blood (1.1.4):     * Presumptive Tests: Initial testing that suggests a substance is probably blood. Examples include Leukocrystal violet ($LCV$), Luminol, and Kastle Meyer.     * Confirmatory Tests: Tests that definitively confirm a substance is blood based on reactions unique to blood chemicals.

• Components of Blood:     * Platelets (Thrombocytes): Tiny cell fragments that assist in blood clotting.     * Red Blood Cells (Erythrocytes): Transport nutrients and oxygen ($O_2$) and remove wastes from the body.     * White Blood Cells (Leukocytes): Active in the immune response. Types include lymphocytes, monocytes, neutrophils, eosinophils, and basophils.     * Plasma: A pale yellowish liquid portion of blood that contains all other components including sugars, lipids, amino acids, and hormones.     * Hemoglobin: A protein in erythrocytes that binds with oxygen for transport.     * Hematocrit: The proportion of red blood cells relative to total blood volume.

• Blood Typing and Compatibility:     * Universal Donor: Blood type $O\,\text{Negative}$.     * Universal Recipient: Blood type $AB$. They can accept any blood type because they do not have antibodies to $A$ or $B$ blood, preventing an immune attack on donor blood.     * Agglutination: If testing shows no agglutination with anti-A or anti-B antibodies, the blood type is $O$ because no antigens are present to react.

Diabetes and Homeostasis

• Comparison of Type 1 and Type 2 Diabetes (2.1.5):     * Symptoms: Both types result in fatigue, dizziness, excessive thirst, and excessive urination.     * Type 1 Treatment: Daily insulin shots or wearing an insulin pump; careful diet and exercise.     * Type 2 Treatment: Weight loss, exercise, oral or injected medications, and careful diet.     * Type 1 Mechanism: The body produces little to no insulin because the beta cells in the pancreas have been damaged (autoimmune response).     * Type 2 Mechanism: Body cells lose receptors for insulin or the receptors are damaged. The body often produces excess insulin to compensate.     * Type 1 Demographic: Can affect anyone, but usually genetic and discovered prior to adulthood.     * Type 2 Demographic: Often adults (middle-aged or older). Overweight contributes, but causes can also be genetic, running in families or specific population groups.

• Feedback Mechanisms:     * Negative Feedback: Mechanisms that return a system to a set point, such as sweating to lower body temperature or increasing respiration when oxygen levels are low. Most body mechanisms are negative.     * Positive Feedback: Mechanisms that amplify a response, such as blood clotting factors attracting more factors or the processes of labor and breastfeeding.

• Macromolecules:     * Lipids: Monomers include fatty acids and glycerol; polymer is triglyceride.     * Carbohydrates: Monomers are monosaccharides; polymers are polysaccharides.     * Proteins: Monomers are amino acids; polymers are proteins.

• Osmosis and Diabetes: Osmosis is the movement of water from high to low concentration. Diabetics experience dehydration because high blood sugar pulls water from cells and tissues into the blood. This causes the kidneys to process more blood and pull out more water for urination, leading to thirst.

• Complications of Diabetes:     * Nerve Damage (Nervous System): High sugar damages nerves, often in the periphery, which can lead to foot amputations.     * Kidney Damage (Urinary System): Overuse and damage to tiny vasculature due to sugar, often accompanied by high blood pressure.     * Heart Disease (Cardiovascular System): Sugar speeds up the buildup of plaque in the arteries.

• Diagnostic Tests for Diabetes:     * Hemoglobin A1C: The definitive test showing average sugar levels over the past $3\,\text{months}$.     * Glucose Tolerance Test ($GTT$): Used to observe glucose tolerance.     * Insulin Level Measurements: To determine insulin production levels.

• Sugar Levels:     * Hyperglycemia: High blood sugar.     * Hypoglycemia: Low blood sugar.

Protein Synthesis and Genetics

• Protein Synthesis Process (2.2.2/2.2.3):     1. Transcription: DNA is transcribed into mRNA within the nucleus.     2. Translation: mRNA leaves the nucleus for the ribosomes. Here, it is translated into codons. tRNA binds to the codons to help synthesize the growing amino acid chain (protein).     * Note: "C" comes before "L" in the alphabet, so Transcription happens before Translation.

• Translation Example:     * DNA Sequence: $TAC\,GGG\,AGA\,CTA\,ATT$     * mRNA: $AUG\,CCC\,UCU\,GAU\,UAA$     * tRNA: $UAC\,GGG\,AGA\,CUA\,AUU$     * Amino Acid Sequence (using mRNA codons): Met/Pro/Ser/Asp/STOP

• Cell Division (2.2.6):     * Mitosis: Creates identical copies of the parent cell for repair and replacement. Results in body cells with $46$ chromosomes.     * Meiosis: Creates sex cells (sperm and egg/gametes) with $23$ chromosomes.

• Inheritance Patterns:     * Sickle Cell Disease (SCD): A recessive hemoglobinopathy (RBC protein disease). Since it is recessive, it may skip generations because individuals can be carriers without having the disease. It causes RBCs to "sickle," leading to anemia and "crises" of extreme pain in joints where vessels are pinched.     * Best’s Disease: A dominant disease. A cross between a woman without the disease ($bb$) and a man with two alleles for the disease ($BB$) results in a $100\,\%$ chance of the child having the disease (all offspring will be $Bb$).     * Familial Hypercholesterolemia ($FH$): A dominant disorder causing high LDL levels. It results from a point mutation in the LDLR gene, affecting the protein that clears LDL from the blood.     * Huntington’s Disease: A dominant disorder.

Cardiovascular Anatomy and Physiology

• Heart Anatomy (1.2.5):     1. Right Atrium.     2. Right Ventricle.     3. Left Atrium.     4. Left Ventricle.     5. Pulmonary Artery.     6. Aorta.     7. Superior Vena Cava.     8. Inferior Vena Cava.     9. Pulmonary Veins.

• Pathway of Blood Flow: Deoxygenated blood enters the superior and inferior vena cavae $\rightarrow$ Right Atrium $\rightarrow$ Tricuspid valve $\rightarrow$ Right Ventricle $\rightarrow$ Pulmonary Artery $\rightarrow$ Lungs $\rightarrow$ Oxygenated blood enters via Pulmonary Veins $\rightarrow$ Left Atrium $\rightarrow$ Bicuspid/Mitral valve $\rightarrow$ Left Ventricle $\rightarrow$ Aortic valve $\rightarrow$ Aorta $\rightarrow$ Body.

• Valve Function: Prevent the backflow of blood. Mitral valve prolapse occurs when valve leaflets do not close fully, causing regurgitation. This can lead to left ventricular hypertrophy (thickening) as the ventricle works harder to pump blood.

• Vital Signs:     * Heart Rate: Number of beats per minute ($\text{bpm}$). Normal range: $60-100\,\text{bpm}$.     * Blood Pressure: Force exerted by blood on artery walls, measured in $\text{mmHg}$. Normal range: $90-120/60-80\,\text{mmHg}$. Measured using a sphygmomanometer and stethoscope.     * Antihypertensives: Medications used to treat high blood pressure include diuretics, betablockers, and calcium channel blockers.

• Electrical Conduction (ECG/EKG): Measures electrical conductivity.     * Pathway: Sinoatrial ($SA$) node (the "pacemaker" at the top of the Right Atrium) $\rightarrow$ Atrioventricular ($AV$) node (bottom of Right Atrium near the septum) $\rightarrow$ Left and Right bundle branches (septum) $\rightarrow$ Purkinje fibers (bottom of ventricles).     * Waves:         1. $P\,\text{wave}$: Atrial contraction (depolarization).         2. $QRS\,\text{complex}$: Ventricular depolarization/contraction. Note: Atrial repolarization is hidden here. The QRS is large due to the size of the ventricles.         3. $T\,\text{wave}$: Ventricular repolarization (relaxation).

• Diagnosis and Conditions:     * Tachycardia: An irregular or high heart rate (e.g., $120\,\text{bpm}$ calculated from $12\,\text{beats}$ in a $6\,\text{second}$ EKG strip).     * Atherosclerosis: Buildup of waxy/fatty substances on vessel walls causing constriction and higher pressure.     * Cholesterol Management:         * LDL: Bad cholesterol; carrier of cholesterol; target level below $100\,\text{mg/dL}$.         * HDL: Good cholesterol; contains more protein; heart protective if above $60\,\text{mg/dL}$ (target above $40-50\,\text{mg/dL}$).         * Medication: Statins like Lipitor.     * Heart Procedures:         * Coronary Artery Bypass Graft (CABG): Most invasive; involves open-heart surgery to bypass blockages using a leg vein.         * Stents: Firm structures placed to hold arteries open.         * Angioplasty: Using a balloon to expand/open the artery.     * Specific Abnormalities: Myocardial infarction (heart attack), Aortic valve stenosis (narrowing), Patent foramen ovale (hole in atria), Ventricular septal defect (hole in septum), and Myocarditis (inflammation).

HIPAA and Ethics

• Definition (2.1.6): Health Information Portability and Accountability Act. Originally created to allow patients to keep insurance coverage when changing jobs; now focused on patient confidentiality.

• Breach Exceptions: HIPAA can legally be broken if:     1. Law enforcement requires it for legal issues.     2. Reporting to the health department for public concern.     3. In an extreme emergency situation.

Infectious Disease and Microbiology

• Disease Transmission: Spread through airborne particles, contact, droplets, food, or vectors.

• Prevention: Hand washing, surface cleaning, vaccination, staying home when sick, and proper food temperature.

• Classes of Pathogens:     * Prions (Non-living): Tiny folded proteins; spread by meat (e.g., Mad Cow/Creutzfeldt Jacob Disease); no treatment.     * Viruses (Non-living): Particles containing DNA/RNA that replicate inside host cells; spread via contact, body fluids, droplets (e.g., COVID, measles, flu).     * Bacteria (Living): Single-celled organisms; treated with antibiotics (e.g., tuberculosis, salmonella, strep throat).     * Fungi (Living): Multicellular plant-like organisms; spread via spores or skin contact; treated with antifungals (e.g., athlete’s foot).     * Helminths (Living): Parasitic worms; spread via food, water, or soil; treated with ivermectin (e.g., tape worms).     * Protists (Living): Single-celled organisms often in water; spread via mosquitoes or stagnant water (e.g., Malaria).

• Bacterial Identification:     * Gram Staining:         * Gram-Positive: Thick peptidoglycan layer traps crystal violet stain; appears blue/dark purple.         * Gram-Negative: Thin peptidoglycan layer; loses crystal violet and takes up Safranin counterstain; appears pink/red.     * Gram Stain Steps: Heat fix $\rightarrow$ Crystal violet ($1\,\text{min}$) $\rightarrow$ Water rinse $\rightarrow$ Iodine ($1\,\text{min}$) to create complex $\rightarrow$ Water rinse $\rightarrow$ Alcohol destain ($6-8\,\text{seconds}$) $\rightarrow$ Water rinse $\rightarrow$ Safranin ($1\,\text{min}$) $\rightarrow$ Water rinse $\rightarrow$ Microscopy.

• Immune System Lines of Defense:     * First Line (Non-specific): Skin, mucus, cilia, inflammation.     * Second Line (Non-specific): White blood cells, phagocytes (macrophages).     * Third Line (Specific): T-cells, B-cells, and antibodies. Vaccines aim to elicit this specific response to create "memory" for future exposure.

• Laboratory Techniques (Culturing): Requires Personal Protective Equipment ($PPE$) and aseptic technique. Involves using a sterile loop to streak bacteria across four quarters of an agar plate to isolate individual colonies.

Critical Study Skills for Assessment

• Utilize health files to differentiate symptoms/diagnoses.

• Identify karyotypes (Male: $XY$, Female: $XX$).

• Understand organ to organ system relationships.

• Calculate using the Glaister Equation for time of death.

• Recognize normal and abnormal vital sign ranges.

• Identify experimental variables: independent, dependent, control, and constants.