Gas Exchange in Biology PDF
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St. Augustine Catholic High School
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Summary
This document explains the process of gas exchange in the lungs and tissues. It also discusses partial pressure and the role it plays in gas exchange. Finally, it describes inhalation, exhalation, and the different respiratory systems.
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1. How Gas Exchange Works Definition: Gas exchange is the diffusion of gases (oxygen and carbon dioxide) across thin membranes in the lungs (alveoli) and tissues. In the Lungs (Alveoli): ○ Oxygen from inhaled air diffuses from the alveoli (high oxygen concentration) into the capi...
1. How Gas Exchange Works Definition: Gas exchange is the diffusion of gases (oxygen and carbon dioxide) across thin membranes in the lungs (alveoli) and tissues. In the Lungs (Alveoli): ○ Oxygen from inhaled air diffuses from the alveoli (high oxygen concentration) into the capillaries (low oxygen concentration). ○ Carbon dioxide moves from the blood (high concentration) to the alveoli (low concentration) to be exhaled. In Tissues: ○ Oxygen from blood diffuses into cells where it’s used for cellular respiration, and carbon dioxide, a waste product, diffuses from cells into the blood. 2. Partial Pressure Definition: Partial pressure is the pressure exerted by each gas in a mixture (e.g., oxygen in air). Role in Gas Exchange: Gases move from areas of higher partial pressure to lower partial pressure. ○ In the Lungs: High partial pressure of oxygen in the alveoli pushes oxygen into the blood. ○ In Tissues: Higher partial pressure of oxygen in the blood drives oxygen into cells, while carbon dioxide moves from cells into the blood. 3. Inhalation (Breathing In) Process: ○ Diaphragm contracts and moves down: Increases the volume of the chest cavity. ○ Intercostal muscles (between ribs) contract: Expands the ribcage outward. Volume and Pressure: ○ Increased volume in the chest cavity lowers pressure in the lungs (compared to the outside air), pulling air in. Air Pathway: Air flows from high pressure (outside) to low pressure (inside lungs) through the nose/mouth → trachea → bronchi → bronchioles → alveoli. 4. Exhalation (Breathing Out) Process: ○ Diaphragm relaxes and moves up: Decreases the volume of the chest cavity. ○ Intercostal muscles relax: The ribcage moves inward. Volume and Pressure: ○ Decreased volume in the chest cavity increases pressure in the lungs, pushing air out. Air Pathway: Air flows from high pressure (inside lungs) to low pressure (outside) through alveoli → bronchioles → bronchi → trachea → nose/mouth. 5. Animal Respiratory Systems (One Multiple Choice Question) Review one key detail for each: ○ Birds: Air sacs allow continuous airflow through lungs, providing a high oxygen level needed for flight. ○ Fish: Gills with counter-current exchange maximize oxygen absorption from water. ○ Insects: Spiracles and tracheae allow direct oxygen delivery to cells. ○ Frogs: Use lungs and skin for gas exchange; skin is effective in water. ○ Humans: Lungs with alveoli provide large surface area for gas exchange. 6. Respiratory System Diagram Pathway: ○ Nasal Cavity → Pharynx → Larynx → Trachea → Bronchi → Bronchioles → Alveoli Key Parts to label: ○ Nasal cavity: Warms and filters air. ○ Trachea: Windpipe carrying air to lungs. ○ Bronchi and Bronchioles: Airways that branch and carry air into the lungs. ○ Alveoli: Tiny sacs where gas exchange happens.