Gas Exchange in Biology PDF

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.