Passive Transport (no energy input required) Passive Transport - - PowerPoint PPT Presentation

Passive Transport

(no energy input required)

Passive Transport

• Passive transport is the movement of ions and
• ther molecules across cell membranes without

the need of energy input (ATP)

• Ions or molecules move from an area of higher

concentration to an area of lower concentration (with the gradient)

• Three types: simple diffusion, facilitated

diffusion, and osmosis

Passive Versus Active Transport

Important Vocabulary

• Concentration gradient – an unequal distribution of

solutes across the cell membrane

• Equilibrium – concentration of molecules is equal

inside and outside of the cell

Concentration Gradient

Simple Diffusion

Simple Diffusion

• Movement of molecules from an area of higher

concentration to an area of lower concentration (with the concentration gradient)

• Molecules will continue to diffuse until equilibrium

is reached

What type of molecules diffuse through the phospholipid bilayer?

• Small non-polar

molecules, such as O2 and CO2

• Some polar

molecules, such as H2O (slowly)

Example of Diffusion

• Simple diffusion is the process by which oxygen and

carbon dioxide are exchanged between the blood cells and body tissues

Facilitated Diffusion

Facilitated Diffusion

• Facilitated diffusion is diffusion that is assisted by

channel or carrier proteins

• Rate of diffusion depends on the number of

proteins available

• Molecules or ions are moving from high to low

concentration

What types of materials are transported by facilitated diffusion?

• Larger molecules such as glucose and amino acids
• Ions (Cl-, K+, Na+ and Ca2+)

Simple Versus Facilitated Diffusion

Complete the following:

• In your notes, create a Venn diagram to

compare and contrast simple and facilitated diffusion

• Watch the following video (3 minutes):

Simple and Facilitated Diffusion

Osmosis

Osmosis

• Diffusion of water across a semi-permeable

membrane

• Water will diffuse to reach equilibrium
• Utilizes specialized channel proteins called

aquaporins

Aquaporins

• Channel proteins that facilitate the diffusion of

water across the membrane

Osmosis

Osmosis and Cells

• Critical balance of water between a cell and its

environment

• Different solutions (environments) can affect a

cells internal water content

Tonicity and Osmosis

Isotonic Environment

• In an isotonic environment, the cell has the same

concentration of dissolved solutes as the surrounding solution

• No net movement of water into or out of the cell
• Cell will retain its shape

Hypotonic Environment

• In a hypotonic environment, the cell has a higher

concentration of dissolved solutes than the surrounding environment

• Water will diffuse into the cell until equilibrium is

reached

• The cell will swell and could possibly burst (lyse)

Hypertonic Environment

• In a hypertonic environment, the cell has a lower

concentration of dissolved solutes than the surrounding environment

• Water will diffuse out of the cell until equilibrium is

reached

• The cell will crenate (shrink)

Adaptations for Osmosis

• Fresh and salt water fish have the ability to
• smoregulate
• Paramecia have a contractile vacuole to control

water intake

Osmosis Reminder: SALT SUCKS!

Osmosis in Plant Cells

• Less affected by osmosis due to protection of

the cell by the cell wall

• Water content affects the size of the vacuole

Plasmolysis Turgid

Plasmolysis

• Cell membrane pulls

away from cell wall,

• ccurs in hypertonic

conditions Turgid (or Turgor Pressure)

• Cytoplasm and vacuole

press against cell wall,

• ccurs in hypotonic

conditions

Complete the following:

• Watch the following video (10 minutes):

Osmosis and Water Potential