Simple Diffusion

By R Marsh, Ph.D.

Simple Diffusion In Cells

Homeostasis:

A process by which biological systems maintain stability while adjusting to changing external conditions

Diffusion

Diffusion

• The net movement of molecules or atoms from one area of high concentration to an area of low concentration.

• ​Caused by random movement.

Gradient: High to Low

Gradient:

The difference in the concentration of a substance between two areas is called the concentration gradient

​

​The bigger the difference, the steeper the concentration gradient and the faster the molecules of a substance will diffuse.

Equilibrium

Equilibrium:

The state in which the concentrations of the diffusing substance in the two compartments are the same or become equal.

​

Equilibrium

Rate of Diffusion:

Can be affected by:

• ​Changes in temperature

• ​Changes in concentration difference (number of atoms)

• ​The medium or what the molecules are diffusing through

Simple Diffusion

The particles move along a concentration gradient in a solution through a semipermeable membrane (barrier that will only allow some molecules to pass through while blocking the passage of other molecules) attain equilibrium on both sides.

​

Simple Diffusion:

​Characteristics

• Across a semipermeable membrane, does not allow everything through.

• ​Requires a concentration gradient across the cell membrane

• ​It is a passive transport mechanism, require no energy

• ​Does not need a carrier transport protein

• ​Random motion

Multiple Choice

Passive Transport uses ____ energy

• no

• a lot of

• a little bit of

• some

Multiple Choice

Passive Transport is the movement of particles across the membrane from an area of [ ___ ] to an area of [ ___ ]

• high to low

• low to high

• low to low

• high to high

Multiple Choice

The condition in which all acting influences are balanced.

• equilibrium

• see-saw

• net movement

• hydrolysis

Multiple Choice

What's another word for equilibrium that means "balanced internal condition of cells?"

• equality

• hydrolysis

• hypertonic

• homeostasis

Multiple Choice

This is when the concentration of particles is higher in one area than another.

• concentration gradient

• concentration

• osmosis

Multiple Choice

What does a 'region with high concentration' mean?

• An area with a SMALL number of particles

• An area with a LARGE number of particles

• An area with an UNEVEN number of particles

• An area with no particles

Multiple Choice

Where is there a low concentration of dye?

• at the bottom of cup

• in the color

• at the top of cup

• no concenteraion gradient

Multiple Choice

When does diffusion stop?

• After a day and a night

• When the particles are evenly spread out

• When there are no particles left

• When all the particles leave the system

Multiple Choice

What happens to particles when they are heated?

• They speed up and spread out
• They slow down and compress
• They stop moving
• They move closer together and speed up

Multiple Choice

What type of diffusion is this:

• simple diffusion

• facilitated diffusion

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