Osmosis

LEARNING GOAL #4

OSMOSIS

L1.3 CELL TRANSPORT

Open Ended

BELLRINGER:

The picture shows the transfer of molecules across the cell membrane.

1. Identify and Describe the process by which O₂ molecules pass through the membrane.

2. Explain how the movement of Na⁺ ions in the picture is different than the movement of O₂ molecules.

LEARNING GOAL #4 - Be sure your notes today can answer these!

•PREDICT HOW OSMOTIC PRESSURE AFFECTS THE
MOVEMENT OF WATER INTO THE CELL.

a.

EXPLAIN OSMOSIS, WITH REGARD TO TONICITY.

b.

DESCRIBE THE THREE DIFFERENT TYPES OF TONICITY
SOLUTIONS.

c.

DESCRIBE WHAT HAPPENS TO PLANT & ANIMAL CELLS WHEN
PLACED IN DIFFERENT TONICITY SOLUTIONS.

d.

EXPLAIN HOW CELLS REGULATE THE AMOUNT OF WATER
WITHIN THE CELL.

OSMOSIS

• OSMOSIS IS THE DIFFUSION OF WATER ACROSS A

SELECTIVELY PERMEABLE MEMBRANE.

• AS TYPE OF PASSIVE TRANSPORT, IT WILL OCCUR UNTIL THE

SOLUTE CONCENTRATION IS BALANCED ON BOTH SIDES OF
THE MEMBRANE.

• POLAR WATER MOLECULES DO NOT DIFFUSE DIRECTLY

THROUGH THE BILAYER

• PASS THROUGH THE CELL MEMBRANE USING CHANNEL

PROTEINS THAT ONLY WATER MOLECULES CAN PASS
THROUGH

• A FORM OF FACILITATED DIFFUSION

OSMOSIS

OSMOSIS - DIFFUSION OF WATER
• AFFECTS THE TURGIDITY OF CELLS
• DIFFERENT SOLUTIONS CAN AFFECT THE INTERNAL

WATER AMOUNT IN THE CELL

Salt Sucks!

Turgidity = the state of the cell being turgid or swollen,
especially due to high fluid
content.

Tonicity = the difference
in solute concentrations
between two solutions

Osmotic pressure = a force
produced by the net movement
of water out of or into a cell
which is driven by differences
in solute concentration.

Simple rule of osmosis

Match

Match the following

• Tonicity

• Turgidity

• Osmotic Pressure

the difference in solute concentrations between two solutions

the state of being turgid or swollen, especially due to high fluid content

a force produced by the movement of water in or out of a cell

• the difference in solute concentrations between two solutions

• the state of being turgid or swollen, especially due to high fluid content

• a force produced by the movement of water in or out of a cell

Dropdown

In osmosis, water moves from a ​

Select answer

solute concentration to ​a

Select answer

solute concentration because it is trying to dilute the solutes.

• ISOTONIC - NO NET MOVEMENT OF WATER MOLECULES

• HYPOTONIC - WATER MOVES INTO THE CELL, & CELL COULD BURST

• HYPERTONIC - WATER MOVES OUT OF THE CELL, & CELL SHRINKS

salty outside

THREE TYPES OF TONICITY

HYPERTONIC

A cell is in a hypertonic solution if
the concentration of solute outside
the cell is HIGHER than the
concentration inside the cell.

Water leaves the cell.

Cell shrinks.

This is why you should NEVER
drink salt water. Doing so will
severely dehydrate you!

Think “SALT SUCKS”

Multiple Choice

Why should you never drink salt water?

• The water will leave your cells because of the isotonic solution surrounding them.

• The water will enter your cells because they are in an hypotonic solution.

• The water will leave your cells because of the hypertonic solution surrounding them.

• Nothing will happen, that's a myth.

HYPOTONIC

•A CELL IS IN A HYPOTONIC
SOLUTION IF THE
CONCENTRATION OF SOLUTE
OUTSIDE THE CELL IS LOWER
THAN THE CONCENTRATION
INSIDE THE CELL.

•WATER ENTERS THE CELL.

•THE CELL CAN BURST IF IT
GETS TOO FULL!

Multiple Choice

True or False: A cell has a high turgidity when it is in a hypotonic solution.

• True

• False

ISOTONIC

SOLUTE CONCENTRATION
STAYS EQUAL INSIDE AND
OUTSIDE THE CELL.

WATER ENTERS AND
LEAVES THE CELL AT
EQUAL RATES.

NO NET MOVEMENT.

Multiple Choice

True or False: there is very little difference in osmotic pressure when a cell is in an isotonic solution.

• True

• False

Open Ended

When a patient is give IV fluids at the hospital, what tonicity should the solution be? Provide a claim to answer the question and justify that claim with reasoning from your notes today.

Turgor pressure occurs in plants cells as their

central vacuoles fill with water.

THE WALLED CELLS OF PLANTS, BACTERIA & FUNGI

Multiple Choice

What happens if you water a plant with salt water?

• It wilts.

• Nothing happens.

• It becomes turgid.

Explain how cells regulate the amount of water

within the cell.

CONTRACTILE VACUOLES
ARE FOUND IN FRESHWATER
MICROORGANISMS - THEY
PUMP OUT EXCESS WATER

Multiple Select

A CELL WAS POISONED BY A SUBSTANCE THAT DESTROYED ALL OF ITS MITOCHONDRIA. WHICH OF THE FOLLOWING CELL TRANSPORT PROCESSES LISTED WOULD STILL BE ABLE TO CONTINUE

• Osmosis

• Simple Diffusion

• Facilitated Diffusion

• Na⁺/K⁺ Pumps

• Phagocytosis

Open Ended

Why did you choose the answers that you did on the last slide?

Open Ended

Chose one of the following to answer based on your notes:

a. explain osmosis, with regard to tonicity,

b. describe the three different types of tonicity solutions,

c. describe what happens to plant and animal cells when placed in different, tonicity solutions,

d. explain how cells regulate the amount of water within the cell.