Diffusion and Osmosis

To remain alive, cells, tissues, and organs must maintain a balance between themselves and the environment. This balance is called homeostasis.

Homeostasis occurs from the organism level all the way down to the cellular level

At the cellular level, homeostasis often begins with diffusion and osmosis

 Molecules are in constant motion. This motion is called Brownian motion. Molecules tend to move from areas of high concentration to areas of low concentration. This is called diffusion.

 

Examples:•Food coloring in water•Cream in coffee•Smoke in the air

Diffusion• Diffusion is the movement of particles

from an area of higher concentration to an area of lower concentration

• Solutions have two parts

oSolute- What is being dissolved.

oSolvent- The liquid in which things are being dissolved

Solutions

SolutionsThe concentration of a solution

is the amount of solute in a solution or over a space

Concentration gradient is the difference in concentration of a substance over a space

Equilibrium is when the amount of substance is equal over space.

In other words – diffusion is the movement of particles along a concentration gradient

•Passive Transport is the movement of molecules without using energy

Diffusion is a type of passive transport

Is there movement of molecules during

equilibrium?

 Diffusion across a membrane.

Some molecules move freely across membranes.

The membrane is called permeable if molecules can pass through

Some membranes are selectively permeable; they allow some molecules to pass through while others may not.

Cells have selectively permeable membranes. These membranes are flexible and are made from 2 layers of phospholipids phospholipidPhospholipid bilayer

Animal cells only have cell membranes

Plant cells have cell membranes and a cell wall

Osmosis 

Osmosis in the diffusion of water across a selectively permeable membrane

Regulating the water flow through the selectively permeable membrane of the cell is an important factor in maintaining homeostasis within a cell

• Most cells whether in multicellular or unicellular organisms, are subject to osmosis because they are surrounded by water solutions.