Principles of Biomedical Science Study Guide Flashcards

Experimental Design and Scientific Methodology

The fundamental components of a controlled experiment are essential for validating scientific hypotheses. A hypothesis is defined as a testable explanation derived from scientific reasoning, typically formatted as: "If [independent variable]…, then [dependent variable]…, because [scientific reasoning]." For instance, a strong hypothesis would be: "If plants receive more sunlight, then plants will grow taller because sunlight increases photosynthesis, which helps make energy."

Variable definitions and specific roles within an experiment include:

Independent Variable (IV): The variable the scientist changes (e.g., the amount of UV light or the use of fertilizer).
Dependent Variable (DV): The variable being measured as the result (e.g., the number of mutations, plant height, or count of dead cancer cells).
Control Group: The group that does not receive the treatment, used for comparison (e.g., plants without fertilizer or cells with $0\,mg/mL$ drug exposure).
Experimental Group: The group receiving the treatment (e.g., plants with fertilizer or cells exposed to cancer drugs).
Constant Variables: Factors kept identical across all groups to ensure results are due to the IV (e.g., same temperature, cell type, soil type, amount of water, and duration of sunlight).
Positive Control: A group expected to show a positive result (e.g., cells treated with a known cancer drug).
Negative Control: A group expected to show no result (e.g., cells with no drug exposure).
Sample Size ( $n$ ): The number of subjects or samples tested (e.g., $1,000,000$ cancer cells). Large sample sizes are important because they reduce the impact of random chance, making results more reliable and accurate.
Replication: Repeating the experiment multiple times (e.g., testing three times) to verify results.

Possible sources of error in experiments, such as uneven sunlight exposure, should be mitigated by placing all subjects in the same location. The iterative design process in biomedical science involves repeating steps to improve a design based on understanding. The steps include: 1. Define the Problem; 2. Research; 3. Brainstorm Solutions; 4. Select and Plan; 5. Build/Implement; 6. Test and Evaluate; 7. Redesign and Repeat. During this process, a Criterion is a feature the design must have to be successful, while a Constraint is a limit the design must follow.

Data Display, Analysis, and Mathematical Applications

Statistical tools and graphs are used to summarize and interpret experimental data:

Line graph: Best for showing change over time or across a continuous IV (e.g., drug concentration versus cell death).
Bar graph: Best for comparing distinct categories or groups.
Standard curve: A graph of known concentrations used to calculate unknown values from absorbance readings (e.g., ELISA or spectrophotometer).
Mean/Average: Calculated as the sum of all values divided by the total number of values to summarize a data set.
Percent change: Calculated as $\frac{\text{Final} - \text{Initial}}{\text{Initial}} \times 100$ to show the magnitude of change.
Conclusion: This must reference the data, state whether the hypothesis was supported or refuted, and address possible sources of error.

Quantitative Calculation Examples:

Percent Error ( $PE$ ): Calculated as $\frac{|\text{Experimental} - \text{Theoretical}|}{\text{Theoretical}} \times 100$ . For an experimental concentration of $3.5\,mg/mL$ versus an expected $4.0\,mg/mL$ , the percent error is: $\text{Percent Error} = \frac{|3.5 - 4.0|}{4.0} \times 100 = 12.5\%$ Potential discrepancies in such measurements can be caused by pipetting mistakes, bubbles, fingerprints, or failing to zero the spectrophotometer.
Algor Mortis (Time of Death): The formula used is: $\text{Time since death (hrs)} = \frac{98.6 - \text{Rectal Temp } ^\circ\text{F}}{1.5}$ Example A: A body discovered at 10:00 PM with a rectal temperature of $93.2\,^\circ\text{F}$ . $\text{Work: } (98.6 - 93.2) \div 1.5 = 3.6\text{ hours}$ Estimated time of death: 6:24 PM. Example B: A body discovered at 8:00 AM with a rectal temperature of $95.2\,^\circ\text{F}$ . $(98.6 - 95.2) \div 1.5 = 2.26... \approx 2.3\text{ hours}$ Estimated time of death: 5:40 AM.
Heart Rate ( $HR$ ) from EKG: Count the number of R-peaks (QRS complexes) in a 6-second strip and multiply by 10.

A strip with 7 complexes: $7 \times 10 = 70\,bpm$ (Normal range: $60-100\,bpm$ ).
A strip with 14 complexes: $14 \times 10 = 140\,bpm$ . This condition is called Tachycardia.

DNA Structure, Protein Synthesis, and Genetics

DNA (Deoxyribonucleic Acid) is composed of four bases. Adenine (A) pairs with Thymine (T), and Guanine (G) pairs with Cytosine (C). Bases are classified as Purines (A, G) or Pyrimidines (T, C). In RNA, Uracil (U) substitutes for Thymine.

Protein Synthesis Process:

Transcription: DNA is transcribed into mRNA in the Nucleus.
Translation: mRNA is translated into protein at the Ribosome. Example: DNA sequence $5'\text{-TAC GGG AGA CTA ATT-}3'$ mRNA: $AUG-CCC-UCU-CAU-UAA$ Amino Acids: Met-Pro-Ser-Asp-Stop

Cell Division Comparison:

Mitosis: Purpose is growth and repair. Resulting cells are 2 identical diploid cells. Chromosome count remains the same as the original ( $46$ ).
Meiosis: Purpose is to make gametes. Resulting cells are 4 genetically different haploid cells. Chromosome count is half the original ( $23$ ).

Genetic Inheritance and Disorders:

Trisomy 21: Results from nondisjunction, a meiosis error.
Sickle cell anemia: Follows an autosomal recessive inheritance pattern. In a cross of carrier parents ( $Bb \times Bb$ ), there is a $25\%$ probability of an affected child.
Best's disease: An autosomal dominant condition.
Familial Hypercholesterolemia (FH): A genetic disorder affecting the LDL receptor, preventing the removal of cholesterol from the blood.
Pedigree Analysis: Recessive traits can be identified if unaffected parents have affected children. Autosomal traits affect both males and females equally, whereas X-linked traits show a sex-dependent pattern.

Molecular Biology and DNA Profiling (MBG-D)

Creating a DNA profile involves four sequential steps:

DNA Extraction: Isolating DNA from cells.
PCR (Polymerase Chain Reaction): Copying specific regions of DNA.
Restriction Digestion: Using restriction enzymes to cut DNA at specific sequences.
Gel Electrophoresis: DNA migrates toward the positive end of the gel because DNA is negatively charged.

Restriction Fragment Length Polymorphism (RFLP) refers to the different sized DNA fragments created by digestion, which are used forensically to identify individuals. Bioinformatics is the use of computers to analyze biological data; Genbank is a common database used for this purpose.

Gel Electrophoresis Interpretation for Genetic Disease:

Disease Allele: Not cut by enzyme (1 band).
Normal Allele: Cut by enzyme (2 bands).
Lane 1 (1 band): Genotype DD (Has disease).
Lane 2 (2 bands): Genotype dd (No disease).
Lane 3 (3 bands - 1 large, 2 small): Genotype Dd (Carrier, no disease).

Cardiovascular Health, Vital Signs, and Pathophysiology

Blood components include Erythrocytes (RBCs) which carry oxygen, Leukocytes (WBCs) which fight infection, Thrombocytes (Platelets) for clotting, and Plasma which carries nutrients, hormones, and waste.

Blood Typing:

Type A: A antigens, Anti-B antibodies.
Type B: B antigens, Anti-A antibodies.
Type AB: A and B antigens, no antibodies. (Universal Recipient).
Type O: No antigens, Anti-A and Anti-B antibodies. (Universal Donor).

Heart Function and Disease:

Blood Flow Path: Body $\rightarrow$ Vena Cava $\rightarrow$ Right Atrium $\rightarrow$ Tricuspid Valve $\rightarrow$ Right Ventricle $\rightarrow$ Pulmonary Artery $\rightarrow$ Lungs $\rightarrow$ Pulmonary Vein $\rightarrow$ Left Atrium $\rightarrow$ Mitral Valve $\rightarrow$ Left Ventricle $\rightarrow$ Aorta $\rightarrow$ Body.
Conduction Path: SA Node $\rightarrow$ AV Node $\rightarrow$ Bundle of His $\rightarrow$ Purkinje Fibers.
EKG Waves: P wave (atrial), QRS (ventricular), T wave (ventricular recovery).
Mitral Valve Prolapse: The valve doesn't close properly, letting blood leak backward. This causes the left ventricle to work harder, leading to left ventricular hypertrophy.
Cholesterol: LDL ("Bad") delivers cholesterol to tissues; healthy targets are low. HDL ("Good") removes cholesterol from blood; healthy targets are high. Atherosclerosis is plaque buildup restricting blood flow.
Treatments for coronary blockage: Least to most invasive include lifestyle changes, medication, and stents.

Homeostasis, Diabetes, and Tonicity

Homeostasis is maintained through feedback loops:

Negative Feedback: Works to counteract a change (e.g., insulin lowering blood glucose, glucagon raising it, or sweating when hot).
Positive Feedback: Works to amplify a change (e.g., clotting factors attracting more factors or labor contractions involving oxytocin).

Diabetes Mellitus:

Type 1: The immune system destroys cells; affects children/teens; treated with insulin injections.
Type 2: Cells become insulin-resistant; affects adults; treated with diet, exercise, and medication.
Diagnosis: Fasting blood glucose threshold is $126\,mg/dL$ . Patient Maria (52) with fasting glucose of $210\,mg/dL$ and HbA1c of $8.2\%$ most likely has Type 2.
Osmosis and Dehydration: High blood glucose pulls water out of cells by osmosis, causing constant dehydration and increased urination.

Osmosis and Tonicity Patient Scenarios:

Isotonic ( $0.9\%\,NaCl$ ): Cells stay the same; no net water movement.
Hypotonic ( $0.45\%\,NaCl$ ): Cells swell; water enters cells.
Hypertonic ( $3\%\,NaCl$ ): Cells shrink; water leaves cells.

Microbiology and Infectious Disease

Classification of Pathogens:

Bacteria: Living; Example - Strep; Treatment - Antibiotics.
Virus: Non-living; Example - Influenza; Treatment - Antivirals/Vaccines.
Fungi: Living; Example - Ringworm; Treatment - Antifungals.
Prion: Non-living; Example - CJD; No cure.

Gram Staining:

Steps: Crystal violet $\rightarrow$ Iodine $\rightarrow$ Alcohol wash $\rightarrow$ Safranin.
Gram Positive: Stains purple due to a thick peptidoglycan layer.
Gram Negative: Stains pink because the alcohol wash removes the outer membrane.

Immune Defense:

1st Line: Skin, mucus, tears (Non-specific).
2nd Line: Inflammation, fever (Non-specific).
3rd Line: B-cells, T-cells, antibodies (Specific). Vaccines rely on this line to provide a safe version of the pathogen for future recognition.

HIPAA and Forensic Science

HIPAA (Health Insurance Portability and Accountability Act) protects patient privacy. It can be broken in specific circumstances such as abuse or public safety. Accurate patient documentation is vital for effective treatment.

Forensic Science Concepts:

Forensic evidence types: Blood, hair, fingerprints, footprints, fibers.
Presumptive Test: Suggests a substance might be present.
Confirmatory Test: Specifically identifies the substance.
Death Classifications: - Cause of Death: What physically caused the death. - Manner of Death: Category (Homicide, Natural, Accident, Suicide, Undetermined). - Mechanism of Death: The physiological body failure.

Questions & Discussion

Q: How does a vaccine work and why does it rely on the 3rd line of defense? A: A vaccine provides a safe version of a pathogen, allowing the specific immune response (B-cells and T-cells) to recognize and remember the pathogen without the patient getting sick.

Q: Identify the organ systems for: Alveoli, Nephron, SA node, Islets of Langerhans, Thymus, Cerebellum, Villus. A: Alveoli (Respiratory), Nephron (Urinary), SA node (Cardiovascular), Islets of Langerhans (Endocrine), Thymus (Immune), Cerebellum (Nervous), Villus (Digestive).