Role of Osmosis and Diffusion in Living Things
Understanding Essential Transport Processes in Plants and Animals
1. Role of Osmosis in Living Things
What is Osmosis?
Osmosis is the movement of water molecules through a selectively permeable membrane from an area of lower solute concentration to an area of higher solute concentration.
1.1 In Plants - Osmosis plays the following roles:
a.  💧 Absorption of water from the soil
Roots absorb water from the soil by osmosis. The root hair cells contain a higher concentration of solutes compared to the surrounding soil water, creating a concentration gradient that drives water uptake into the plant's root system.
b.  🌿 Support
Some plants have cells that absorb water, become turgid hence providing support to the plants. This turgor pressure helps maintain the plant's upright structure and prevents wilting.
c.  🪲 Feeding in insectivorous plants
Insectivorous plants such as pitcher plant prey on insects. They trap insects when there is a sudden change in their stiffness when disturbed by the insect. Trapped insects are digested to provide the plant with nitrogen.
1.2 In Animals - Osmosis plays the following roles:
a. 💧 Absorption of water in the human body
Osmosis facilitates water absorption throughout the human body, including in the digestive system where water moves across cell membranes, and in maintaining proper cellular hydration.
b. 🚰 Excretion
This is the removal of waste products from the body. Urine is the main product through which excess water is excreted from the body. Kidneys filter urine to control the amount of water lost. This happens through osmosis.
2. Role of Diffusion in Living Things
What is Diffusion?
Diffusion is the movement of particles from an area of higher concentration to an area of lower concentration until equilibrium is reached.
2.1 In Plants - Diffusion plays the following roles:
a. 🌬️ Gas exchange during photosynthesis and respiration
Carbon dioxide diffuses from the air into plant leaves through stomata for photosynthesis, while oxygen produced during photosynthesis diffuses out of the leaves into the atmosphere.
b. 🌱 Transport of nutrients and minerals
Dissolved nutrients and minerals diffuse from areas of high concentration to areas of low concentration within plant tissues, ensuring proper distribution throughout the plant.
2.2 In Animals - Diffusion plays the following roles:
a.  🫁 Gas exchange in lungs
Oxygen diffuses from the air in the lungs into the bloodstream, while carbon dioxide diffuses from the blood into the lungs to be exhaled.
b. 🍎 Absorption of nutrients in the digestive system
Digested nutrients diffuse from the intestines into the bloodstream for distribution to body cells.
c. 🗑️ Removal of waste products
Waste products like urea diffuse from body cells into the bloodstream and are transported to excretory organs for removal.
3. Similarities and Differences between Osmosis and Diffusion
3.1 Similarities
1 Both are meant to equalize concentration of two solutions
2 Both are passive transport processes, i.e., they do not require any energy to occur
3 In both, particles move from an area of higher concentration to an area of low concentration
3.2 Differences
1 Medium of occurrence:
✓ Osmosis: Happens in liquid medium only
✓ Diffusion: Happens in liquids, gases and even solids
2 Membrane requirement:
✓ Osmosis: Semi-permeable membrane is required
✓ Diffusion: No membrane is needed
3 Water requirement:
✓ Osmosis: Requires water for movement of particles
✓ Diffusion: Does not require water
4 Direction of particle flow:
✓ Osmosis: There is only one way for particles to flow
✓ Diffusion: Particles can flow in any direction
🎯 Summary
Both osmosis and diffusion are essential biological processes that maintain life in plants and animals. While they share similarities as passive transport mechanisms, they differ in their requirements and applications. Understanding these processes helps us appreciate how living organisms maintain their cellular functions and survive in their environments.
Last modified: Thursday, 31 July 2025, 2:47 PM