1.3.7 Transport Summary & Applications

1. Diffusion:

• Definition: The movement of particles from an area of higher concentration to an area of lower concentration until equilibrium is reached.
• Type: Passive (no energy required).
• Example: Oxygen diffusing from the alveoli into the blood.

2. Osmosis:

• Definition: The diffusion of water molecules across a partially permeable membrane from an area of higher water concentration (lower solute concentration) to an area of lower water concentration (higher solute concentration).
• Type: Passive (no energy required).
• Example: Water moving into plant roots from the soil.

3. Active Transport:

• Definition: The movement of particles from an area of lower concentration to an area of higher concentration, against the concentration gradient, using energy from respiration.
• Type: Active (energy required).
• Example: Mineral ions being absorbed into root hair cells from the soil.

Applications of Transport Mechanisms:

1. In Plants:

• Water Uptake and Nutrient Absorption:
• Osmosis allows water to enter plant roots from the soil, keeping the plant hydrated and supporting cell turgidity.
• Active transport is used to absorb essential mineral ions like potassium and nitrate from the soil, even when their concentration in the soil is lower than in the root cells. This is vital for plant growth and development.
• Photosynthesis:
• Diffusion of carbon dioxide into leaf cells is essential for photosynthesis, where it is used to produce glucose and oxygen.

2. In Humans:

• Gas Exchange in the Lungs:

• Diffusion of oxygen from the alveoli into the blood and carbon dioxide from the blood into the alveoli is crucial for respiration.

  

• Nutrient Absorption in the Gut:

• Active transport is used to absorb glucose and amino acids from the small intestine into the blood, ensuring that the body can access energy and building blocks for growth, even when nutrient concentrations in the gut are low.

• Kidney Function:

• Osmosis helps in the reabsorption of water in the kidneys, regulating water balance in the body and forming concentrated urine.

• Active transport is used to reabsorb useful substances like glucose and ions back into the blood from the kidney tubules.

3. Cellular Homeostasis:

• All cells rely on diffusion, osmosis, and active transport to maintain a stable internal environment, or homeostasis. This includes balancing ion concentrations, nutrient levels, and water content, which are all essential for normal cell function and survival.

Summary:

• Diffusion and osmosis are passive processes that do not require energy, whereas active transport requires energy to move substances against their concentration gradient.
• These transport mechanisms are essential for various biological processes, such as nutrient absorption, gas exchange, water balance, and overall cellular homeostasis.
• Understanding these processes and their applications helps us appreciate how organisms maintain life and adapt to their environments.