UNIT 3 BIO211 ESSAY QUESTIONS

1. Describe the difference between innate and adaptive immunity. Give examples of each.

Innate immunity is the body’s first line of defense and is non-specific, meaning it attacks anything that looks foreign. Examples include physical barriers like skin, mucous membranes, and cells like macrophages and neutrophils that eat pathogens. Adaptive immunity is specific and develops over time, targeting particular invaders with memory cells for faster future responses. Examples of adaptive immunity include B cells producing antibodies against a specific virus and T cells attacking infected cells.

1. Discuss cell mediated immunity versus humoral immunity. Give examples of each. 

Cell-mediated immunity involves T cells attacking infected or abnormal cells directly. It is effective against viruses, fungi, and cancer cells. Humoral immunity involves B cells producing antibodies that float in the blood or lymph to neutralize pathogens. Humoral immunity is mainly effective against bacteria and toxins in body fluids.

1. Explain the process of cell mediated immunity (specify the types of cells involved and the role of MHC proteins and CDs in this process).

Cell-mediated immunity starts when a pathogen infects a body cell, and that cell shows a piece of the pathogen on MHC class I proteins. Cytotoxic T cells (CD8+) recognize this and destroy the infected cell. Helper T cells (CD4+) can also help by releasing cytokines to activate other immune cells. This system is mainly for killing infected or abnormal cells rather than attacking pathogens in body fluids.

1. Explain the process of humoral or antibody mediated immunity. 

Humoral immunity begins when B cells encounter a specific antigen, sometimes with help from helper T cells. The B cells divide and turn into plasma cells that make antibodies specific to that antigen. Antibodies circulate in the blood and lymph, binding to pathogens to neutralize them or mark them for destruction by other immune cells. Some B cells become memory B cells, which respond faster if the pathogen returns.

1. What is an immunoglobulin (Ig)? Briefly describe its structure. List and describe the functions of the five major classes of immunoglobulins found in the body.

An immunoglobulin (Ig) is a protein antibody made by B cells that recognizes specific antigens. Structurally, it has two heavy chains and two light chains forming a Y shape, with variable regions that bind the antigen. The five major classes are:

• IgG – most common, crosses the placenta, fights bacteria and viruses.

• IgA – found in secretions like saliva and breast milk, protects mucosal surfaces.

• IgM – first antibody produced in an infection, very effective at clumping pathogens.

• IgE – involved in allergies and defense against parasites.

• IgD – mainly acts as a receptor on immature B cells to start immune responses.

1. Define active immunity and passive immunity and give examples of each. 

Active immunity happens when the body produces its own antibodies in response to an infection or vaccine. For example, getting the flu shot gives you active immunity against influenza. Passive immunity is when you receive antibodies made by another person or animal, which gives immediate protection but does not last long. An example is a baby receiving antibodies through breast milk or a patient getting an antibody injection after exposure to a virus.

1. Differentiate between: a) pulmonary ventilation and alveolar ventilation, b) alveolar gas exchange and systemic gas exchange, c) quiet and forced breathing and d) inhalation and exhalation.

Pulmonary ventilation is the total movement of air into and out of the lungs, basically breathing in and out. Alveolar ventilation is the amount of air that actually reaches the alveoli and participates in gas exchange. So, not all air we breathe in reaches the alveoli because some fills the airways (dead space). Alveolar ventilation is more important for determining how much oxygen enters the blood.

1. Discuss the general relationship between gas pressure and volume including Boyle’s law.

Boyle’s law says that gas pressure and volume are inversely related when temperature is constant. This means if volume goes up, pressure goes down, and if volume goes down, pressure goes up. In the lungs, expanding the thoracic cavity lowers pressure, so air flows in during inhalation. Decreasing thoracic volume raises pressure, pushing air out during exhalation.

1. Discuss the concept of Dalton's Law and its relation to partial pressure.  

Dalton’s Law says that the total pressure of a gas mixture is the sum of the pressures of each individual gas. Each gas in the mixture contributes a partial pressure based on its proportion. In the lungs, this is important because oxygen and carbon dioxide move according to their partial pressures. Gases always diffuse from areas of higher partial pressure to lower partial pressure.

1. Define Henry’s law and explain gas solubility. Which gas out of CO2, O2 and N2, is the most soluble and which one is the least soluble in blood?

Henry’s law states that the amount of gas that dissolves in a liquid is proportional to its partial pressure. Gas solubility also depends on the type of gas—some gases dissolve more easily in liquids than others. In blood, carbon dioxide (CO₂) is the most soluble, oxygen (O₂) is less soluble, and nitrogen (N₂) is the least soluble. This is why CO₂ moves easily between blood and tissues, while N₂ mostly stays in gas form.

1. How does partial pressure help gases move across the respiratory membrane during alveolar gas exchange? How does partial pressure help gases move across the capillary endothelium during systemic gas exchange?

During alveolar gas exchange, oxygen moves into the blood because its partial pressure is higher in the alveoli than in the blood, and carbon dioxide moves into the alveoli because its partial pressure is higher in the blood than in the alveoli. This pressure difference drives gas diffusion. During systemic gas exchange, oxygen moves from blood to tissues because blood has a higher oxygen partial pressure than the tissues, while carbon dioxide moves from tissues to blood because tissues have a higher carbon dioxide partial pressure than the blood. Gases always move from areas of higher partial pressure to lower partial pressure.

1. Explain how pressure gradients and resistance determine airflow. Include an example of a disease that would obstruct airflow.  

Airflow depends on pressure gradients and resistance in the airways. Air moves from areas of higher pressure to lower pressure, and the bigger the difference, the faster the airflow. Resistance, caused by airway size or obstruction, slows airflow, making breathing harder. For example, asthma increases airway resistance, reducing airflow and making it difficult to breathe.

1. Define the following terms: tidal volume, anatomical dead space, expiratory reserve volume, inspiratory reserve volume, and residual volume. Compare and contrast the formulas that calculate vital capacity and total lung capacity.

Tidal volume (TV) is the amount of air you breathe in or out during a normal breath, while anatomical dead space is the air in the airways that never reaches the alveoli and doesn’t participate in gas exchange. Expiratory reserve volume (ERV) is the extra air you can force out after a normal exhale, and inspiratory reserve volume (IRV) is the extra air you can force in after a normal inhale. Residual volume (RV) is the air that always stays in the lungs even after maximum exhalation. Vital capacity (VC) equals IRV + TV + ERV, which is the total usable air you can move, whereas total lung capacity (TLC) equals VC + RV, including all air in the lungs, so TLC is always larger than VC.