Gaseous Exchange in Living Organisms

Gaseous Exchange in Living Organisms

• Aerobic respiration requires a constant supply of oxygen and expulsion of carbon dioxide.
• Organisms have specialized gas exchange organs (like lungs or gills) for this process.
• Gas exchange occurs by diffusion, moving molecules from high to low concentration.
• Cellular respiration is the process of breaking down food molecules to release energy.
• Breathing involves moving air in and out, necessary for gas exchange.
• Diffusion is the movement of molecules from high to low concentration.
• Surface area-to-volume ratio significantly impacts gas exchange. Small organisms have a larger ratio, allowing for diffusion across their body surface, whereas larger organisms need specialised structures.
• Specialized structures like gills and lungs provide large surface areas for efficient gas exchange in larger organisms.

Key Concepts

• Cellular respiration: A chemical process in cells that breaks down food molecules to release energy.
• Breathing: The physical process of moving oxygen-rich air into the lungs and expelling carbon dioxide-rich air.
• Gas exchange: The process of oxygen and carbon dioxide diffusing across a surface or membrane.

Specialized Structures in Larger Organisms

• Gas exchange organs (like gills or lungs) with specialized surfaces offer a large surface area.

Gaseous Exchange In Specific Organisms

• Earthworms: Diffuse gases across their thin, permeable body surface, kept moist by mucus.
• Locusts: Utilize a tracheal system and spiracles for gas exchange, regulated via movements.
• Bony Fish: The gills, containing filaments and lamellae, provide a large surface area for efficient water-based gas exchange.
• Dicotyledonous Plants: Gas exchange mainly occurs through stomata, controlled by guard cells, within the leaves.
• Mammals: Alveoli in the lungs facilitate oxygen and carbon dioxide exchange.

The Breathing (Ventilation) System

• The nose leads to nasal passages.
• The nasal cavity contains conchae to increase surface area and warm/filter air.
• The pharynx connects the nasal cavity to the larynx (voice box).
• The larynx contains vocal cords.
• The epiglottis prevents food from entering the trachea.
• Bronchi branch from the trachea into each lung.
• Bronchioles are smaller branches of the bronchi, within the lungs.
• Alveoli are tiny air sacs within the lungs that facilitate gas exchange (with a network of capillaries).
• Cilia sweep mucus and trapped particles away from the lungs.
• The two lungs are spongy organs in the chest cavity. They each have multiple lobes.
• The alveoli have a large surface area for gas exchange.

Gaseous Exchange and Transport of Gases

• Blood brings deoxygenated blood to the alveoli.
• Oxygen diffuses from the alveoli into the blood.
• Oxygen binds to haemoglobin in red blood cells, becoming oxyhemoglobin.
• Oxygen is transported to body tissues.
• Carbon dioxide diffuses into the blood from body tissues (it's a byproduct of cellular activities)
• Carbon dioxide is transported in blood in various forms.

Transport of Carbon Dioxide

• Some CO2 dissolves in the blood plasma.
• Some binds to haemoglobin.
• Most is carried as bicarbonate ions.
• CO2 diffuses from the blood to the alveoli for exhalation.

Gaseous Exchange: A Detailed Overview

• Gaseous exchange is the process of obtaining oxygen for respiration and expelling carbon dioxide.
• It primarily happens through diffusion across respiratory surfaces from high to low concentrations.

Adaptations for Gas Exchange in Different Organisms

• Unicellular organisms use direct diffusion.
• Small multicellular organisms use their moist skin.
• Fish use gills with lamellae.
• Insects use a tracheal system.
• Plants use stomata.
• Mammals use lungs with alveoli.

Regulation of Breathing and Homeostasis

• The medulla oblongata controls breathing rates based on carbon dioxide levels.
• Breathing rates adjust to exercise and altitude.

Measurement of Lung Capacity

• Spirometers measure vital capacity and tidal volume.

Effects of Physical Activity on Breathing

• Breathing rate and depth increase during exercise.

Common Respiratory Diseases

• Tuberculosis
• Asthma
• Hay Fever
• Bronchitis
• Emphysema

Effects of Smoking on Health

• Nicotine, tar, and carbon monoxide negatively impact health.