Diffusion and Transport

Ms. KlinkhachornNovember 29, 2010

AP Biology

Announcements:

• Quiz on THURSDAY– Organelles– Eukaryotes and Prokaryotes– Plant Cells and Animal Cells– Membranes– Passive Transport

Identify the Parts

Phospholipid Bilayer - Characteristics

Permeability of the Bilayer

• Hydrophobic molecules can pass through, but hydrophilic molecules can not (at least not easily)– Polar molecules = hydrophilic• Examples: Sugars, charged atoms (K+) and molecules

– Nonpolar molecules = hydrophobic• Examples: oxygen, carbon dioxide

Transport Proteins

• Help materials that are big or hydrophilic pass through the membrane easily– Substance specific• If it’s supposed to translocate water and sugar, it will

only translocate water and sugar

• Two Kinds:– Channel Proteins– Carrier Proteins

Transport Proteins

Efficacy of Transport Proteins

• 3 billion water molecules can move across the membrane using an aquaporin per second

• Glucose moves across the membrane 50,000x faster with a transport protein than by itself

Passive Transport

• Diffusion ACROSS A MEMBRANE– Diffusion = movement of molecules so that they

spread out evenly in an available space • Does NOT require energy or use a transport protein• Once the molecules spread out they are in a state of

equilibrium

• Substances diffuse from a high concentration to a low concentration– They move down their own concentration

gradient

Diffusion of Sugar

Concentration Gradient

Types of Passive Transport

• Simple Diffusion• Facilitated Diffusion• Osmosis

Example: Gas Exchange

Simple Diffusion

Facilitated Diffusion

• Diffusion that requires a transport protein

Osmosis

• Diffusion of water across a selectively permeable membrane (where the solute cannot go through the membrane)

• Water will move from an area of lower solute concentration to an area of higher solute concentration– Wants to balance out the solute concentrations

Osmosis

Hypertonic Solutions

• “Hyper” means “above”• A hypertonic solution has a higher

concentration of solute– This means that water is less concentrated

• A cell placed in a hypertonic solution will SHRINK due to water loss.

Plant Cells in a Hypertonic Solution

Before and After

Hypotonic Solutions

• “Hypo” means “below”• A hypotonic solution has a lower

concentration of solute– This means that water is more concentrated

• A cell placed in a hypotonic solution will SWELL due to water intake.

Isotonic Solutions

• “Iso” means “equal”• An isotonic solution has an equal

concentration of solute• A cell placed in an isotonic solution will remain

unchanged• There will still be movement of water, though

there is NO NET GAIN.

DNA – November 30, 2010

Answer these on the back of your study guide:1. What is diffusion? How is it different from

passive transport?2. What do the word forms “hypo”, “hyper”,

“osmo” and “iso” mean?3. Describe what is happening in the picture.

Water Balance in Animal Cells

• If the cell swells too much, it can burst. – This is called lysis. The cell lyses.

• If the cell shrivels too much, it can die.

Examples (Animal Cell)

Water Balance in Plant Cells• Cells still swell in hypotonic environment, but the

wall is more rigid.– Water uptake makes the cell turgid (firm).

• This is a plant’s healthy state.• If the cell is in an isotonic environment, it is

flaccid (limp)• If the cell is in a hypertonic environment, it

plasmolyzes (a process called plasmolysis)– The cell membrane pulls away from the cell wall as

water is lost– Can cause death.

Examples (Plant Cell)

Saltwater fish – Predict what happens to fish in these environments.

Saltwater Fish

• Saltwater fish are constantly swimming in a hypertonic environment

• Fish are consistently losing water from their bodies

• In order to maintain water balance, the fish have to drink a lot of saltwater and pump salt out of their bodies

Freshwater fish – Predict what happens to fish in these environments.

Freshwater Fish

• Freshwater fish live in a hypotonic environment

• Water is constantly moving into their cells

• These fish pee regularly in order to get rid of this water

Osmoregulation

• Osmoregulation = the control of water balance

• Certain organisms are adapted to deal with this– Sea animals – Paramecium

Paramecium

• Paramecium lives in pond water, which is hypotonic to the cell.

• What effect does the hypotonic environment have on this?

• How might the paramecium adapt?

Contractile Vacuole

DNA – December 1, 2010

1. Give an example of how organisms have adapted to deal with hypertonic or hypotonic living conditions.

2. Explain what a hypertonic and a hypotonic environment will do to a piece of celery.

Osmosis Practice

Active Transport

• Active transport = movement of substances AGAINST their concentration gradient– Requires energy ATP– Uses a transport protein, specifically a carrier

protein

• This allows cells to maintain certain solute concentrations

Sodium-Potassium Pump