ZOL2604
ASSIGNMENT 3 2025
UNIQUE NO.
DUE DATE: 2025
, ZOL2604 – Physiology and Embryology Concepts
Assessment 3 – 2025
Question 1 – Practical applications of osmosis and diffusion in nature (10)
Osmosis and diffusion are passive transport processes essential for life. They allow the
movement of water and solutes across membranes without requiring energy.
Example 1: Water absorption by plant roots
In plants, osmosis enables the uptake of water from the soil into root hair cells,
where the water potential inside the cell is lower than in the surrounding soil.
The absorbed water moves through the cortex into the xylem, contributing to the
transpiration stream. This maintains plant turgidity, enabling upright growth and
photosynthesis (Taiz et al., 2015).
Example 2: Gas exchange in the human lungs
In the alveoli, diffusion allows oxygen to move from an area of higher partial
pressure in inhaled air (~100 mmHg) into the deoxygenated blood (~40 mmHg),
while carbon dioxide diffuses in the opposite direction.
This process ensures efficient respiration without active transport, enabling
continuous supply of oxygen for cellular metabolism and removal of metabolic
waste gases (Hall & Hall, 2021).
Example 3: Kidney filtration
In the nephron, diffusion and osmosis regulate the movement of water and
solutes such as sodium, potassium, and urea.
Water reabsorption in the collecting ducts is largely osmotic, influenced by
antidiuretic hormone (ADH) (Guyton & Hall, 2021).
ASSIGNMENT 3 2025
UNIQUE NO.
DUE DATE: 2025
, ZOL2604 – Physiology and Embryology Concepts
Assessment 3 – 2025
Question 1 – Practical applications of osmosis and diffusion in nature (10)
Osmosis and diffusion are passive transport processes essential for life. They allow the
movement of water and solutes across membranes without requiring energy.
Example 1: Water absorption by plant roots
In plants, osmosis enables the uptake of water from the soil into root hair cells,
where the water potential inside the cell is lower than in the surrounding soil.
The absorbed water moves through the cortex into the xylem, contributing to the
transpiration stream. This maintains plant turgidity, enabling upright growth and
photosynthesis (Taiz et al., 2015).
Example 2: Gas exchange in the human lungs
In the alveoli, diffusion allows oxygen to move from an area of higher partial
pressure in inhaled air (~100 mmHg) into the deoxygenated blood (~40 mmHg),
while carbon dioxide diffuses in the opposite direction.
This process ensures efficient respiration without active transport, enabling
continuous supply of oxygen for cellular metabolism and removal of metabolic
waste gases (Hall & Hall, 2021).
Example 3: Kidney filtration
In the nephron, diffusion and osmosis regulate the movement of water and
solutes such as sodium, potassium, and urea.
Water reabsorption in the collecting ducts is largely osmotic, influenced by
antidiuretic hormone (ADH) (Guyton & Hall, 2021).
