krit.club logo

Biology: Human Physiology, Health, and Response - Disease, Pathogens, Immunity, Vaccination, and Autoimmune Disorders

Grade 8IB

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

•

Pathogens: Microorganisms that cause infectious disease. The four main types are bacteria, viruses, fungi, and protists. Bacteria are prokaryotic and reproduce via binary fission, while viruses require a host cell to replicate by injecting their genetic material (DNADNA or RNARNA).

•

First Line of Defense: Physical and chemical barriers that prevent pathogen entry. These include the skin, mucous membranes, and stomach acid (Hydrochloric acid, HClHCl, with a pH≈2pH \approx 2).

•

Second Line of Defense (Innate Immunity): A non-specific response involving phagocytes (white blood cells) that engulf and digest pathogens through phagocytosis. This often results in inflammation and fever.

•

Third Line of Defense (Adaptive Immunity): A specific response involving Lymphocytes. B-cells produce YY-shaped proteins called antibodies that bind to specific antigens. T-cells identify and destroy infected body cells.

•

Vaccination: The process of inducing artificial active immunity. A weakened or inactive form of a pathogen is introduced, stimulating the production of memory cells. This ensures that a secondary immune response is much faster and stronger than the primary response.

•

Autoimmune Disorders: A condition where the immune system fails to distinguish 'self' from 'non-self.' It produces antibodies that attack the body's own healthy tissues (e.g., Type 1 Diabetes, where the immune system destroys insulin-producing cells in the pancreas).

•

Antibiotics vs. Antivirals: Antibiotics (like Penicillin) kill bacteria by disrupting cell wall synthesis or metabolism but are ineffective against viruses because viruses lack these structures and reside inside host cells.

📐Formulae

N=N0×2nN = N_0 \times 2^n (Bacterial growth through binary fission, where nn is the number of generations)

n=TtotalTgenerationn = \frac{T_{total}}{T_{generation}} (Calculating number of generations over time)

BMI=mass (kg)height2 (m2)BMI = \frac{mass\text{ (kg)}}{height^2\text{ (m}^2\text{)}} (Body Mass Index used to assess health risks)

Efficiency of Vaccine (%)=Infection Rateunvaccinated−Infection RatevaccinatedInfection Rateunvaccinated×100\text{Efficiency of Vaccine (\%)} = \frac{\text{Infection Rate}_{unvaccinated} - \text{Infection Rate}_{vaccinated}}{\text{Infection Rate}_{unvaccinated}} \times 100

💡Examples

Problem 1:

A population of bacteria starts with N0=500N_0 = 500 cells. If the bacteria divide every 2020 minutes, calculate the total number of bacteria (NN) after 22 hours.

Solution:

First, find the number of generations (nn): 2 hours=120 minutes2\text{ hours} = 120\text{ minutes} n=12020=6 generationsn = \frac{120}{20} = 6\text{ generations} Now, use the growth formula: N=500×26N = 500 \times 2^6 N=500×64N = 500 \times 64 N=32,000 bacteriaN = 32,000\text{ bacteria}

Explanation:

Since bacteria double every generation, we use an exponential growth model based on the number of 2020-minute intervals in 22 hours.

Problem 2:

An individual has a mass of 70 kg70\text{ kg} and a height of 1.75 m1.75\text{ m}. Calculate their BMIBMI and determine if it falls within the healthy range (18.518.5 to 24.924.9).

Solution:

BMI=701.752BMI = \frac{70}{1.75^2} BMI=703.0625BMI = \frac{70}{3.0625} BMI≈22.86BMI \approx 22.86

Explanation:

The calculated BMIBMI is approximately 22.8622.86. Since 18.5<22.86<24.918.5 < 22.86 < 24.9, the individual is within the healthy weight range.

Problem 3:

Describe the difference between the primary and secondary immune response in terms of antibody concentration.

Solution:

In the primary response, there is a lag phase while B-cells identify the antigen; antibody concentration rises slowly and peaks at a lower level. In the secondary response (upon re-exposure), memory cells recognize the antigen immediately. This leads to a rate of production where Ratesecondary≫RateprimaryRate_{secondary} \gg Rate_{primary}, and the peak concentration is significantly higher.

Explanation:

This demonstrates the effectiveness of immunological memory provided by vaccinations or previous infections.