Diffusion Revision Notes

Particles such as molecules and ions are constantly moving in all directions unpredictably due to their kinetic energy.

This random motion means particles collide and spread out over time.

• Particles move in random directions
• Movement is continuous and constant

When there is a difference in particle concentration between two areas, particles tend to spread from the area with more particles (higher concentration) to the area with fewer particles (lower concentration).

This results in a net movement of particles down the concentration gradient.

• Particles move from high to low concentration
• Movement continues until concentrations equalize

Diffusion does not require energy input from cells or organisms; it happens naturally due to particle motion.

It is essential for processes like gas exchange and nutrient absorption in living organisms.

• No energy required
• Important for biological functions

Molecules and ions possess kinetic energy, which is the energy of motion.

This energy causes them to move randomly in all directions constantly.

• Kinetic energy = energy of motion
• Particles move unpredictably due to kinetic energy

Because particles move randomly, they spread out from crowded areas to less crowded areas.

This spreading out is the basis of diffusion, moving substances down their concentration gradient.

• Random motion causes particles to spread
• Leads to net movement from high to low concentration

Diffusion is a passive process powered by the particles' own kinetic energy.

Cells do not need to use energy to make diffusion happen.

• Diffusion requires no external energy
• Energy comes from particle motion itself

The cell membrane controls what substances can enter or leave the cell.

It allows small molecules like oxygen and carbon dioxide to pass through by diffusion.

Larger molecules usually cannot diffuse directly through the membrane.

• Cell membrane is selectively permeable
• Allows small molecules to diffuse
• Blocks large molecules

Oxygen moves from outside the cell, where its concentration is higher, into the cell by diffusion.

Carbon dioxide moves from inside the cell, where its concentration is higher, out into the surroundings by diffusion.

This exchange supports cellular respiration and waste removal.

• Oxygen enters cells by diffusion
• Carbon dioxide leaves cells by diffusion

Diffusion across the cell membrane is a passive process and does not require energy from the cell.

Movement occurs down concentration gradients until equilibrium is reached.

• No energy required
• Movement down concentration gradient

Oxygen diffuses from areas of higher concentration outside cells into cells where it is used for respiration.

Carbon dioxide, a waste product of respiration, diffuses out of cells where its concentration is higher into the surrounding fluid where it is lower.

This exchange is critical for cellular energy production and waste removal.

• Oxygen enters cells by diffusion
• Carbon dioxide leaves cells by diffusion

Nutrients dissolved in body fluids diffuse into cells to provide materials for growth and metabolism.

Waste substances produced by cells diffuse out into body fluids to be eliminated.

Diffusion maintains the balance of substances needed for cell survival.

• Nutrients enter cells by diffusion
• Waste products leave cells by diffusion

Diffusion is a passive process that does not require energy from cells.

It helps maintain stable internal conditions by regulating the movement of gases and solutes.

In large organisms, diffusion is supplemented by circulatory systems to transport substances efficiently.

• No energy required
• Maintains homeostasis
• Supports respiration and metabolism

A larger surface area allows more particles to diffuse simultaneously, increasing the overall rate of diffusion. Biological structures like alveoli have large surface areas to maximize diffusion efficiency.

• More surface area means more space for particles to cross.
• Increasing surface area speeds up diffusion.

Higher temperatures increase the kinetic energy of particles, causing them to move faster and collide more often, which speeds up diffusion.

• Temperature rise increases particle movement speed.
• Diffusion rate increases with temperature until other factors limit it.

A steeper concentration gradient means a larger difference in concentration between two areas, providing a stronger driving force for particles to move from high to low concentration.

• Greater concentration difference increases diffusion rate.
• As gradient decreases, diffusion slows down.

The shorter the distance particles must travel, the faster diffusion occurs because particles have less space to cover.

• Thin membranes reduce diffusion distance.
• Shorter distance increases diffusion speed.