Section Objectives

1

• Section Objectives
• Explain how the processes of diffusion, passive
  transport, and active transport occur and why
  they are important to cells.
• Predict the effect of a hypotonic, hypertonic, or
  isotonic solution on a cell.

2
Today you will learn about

1. Passive Transport
2. Osmosis
3. Osmosis within the 3 types of solutions.

3
Osmosis Movement of Water

• Diffusion is the movement of particles from an
  area of higher concentration to an area of lower
  concentration.
• In a cell, water always moves to reach an equal
  concentration on both sides of the membrane.

4
Osmosis Movement of Water

• The movement of water across a selectively
  permeable membrane is called osmosis.
• Regulating the water flow through the plasma
  membrane is an important factor in maintaining
  homeostasis within a cell.

5
What controls osmosis?

• Unequal distribution of particles, called a
  concentration gradient, is one factor that
  controls osmosis.
• .

After Osmosis
Before Osmosis
Selectively permeable membrane
Water molecule Sugar molecule
6
Osmosis Diffusion of Water

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

7
Types of Cellular Transport

• Passive Transport
• cell doesnt use energy
• Diffusion
• Facilitated Diffusion
• Osmosis
• Active Transport
• cell does use energy
• Protein Pumps
• Endocytosis
• Exocytosis

8
3 Types of Passive Transport

• Diffusion molecules move high to low.
• Facilitative Diffusion diffusion with the help
  of transport proteins.
• Osmosis Water moves high to low.

9
Passive Transport 1. Osmosis

• 1.Osmosis diffusion of water through a
  selectively permeable membrane.
• Water moves from high to low concentrations.

• Water moves freely through pores.
• Solute (green) too large to move across.

10
Effects of Osmosis on Life

• Osmosis- diffusion of water through a selectively
  permeable membrane.
• There are 3 types of solutions
• Isotonic
• Hypertonic
• Hypotonic

11
Isotonic Solution

• Solutions that contain the same concentration of
  solutes as the cytoplasm are called isotonic (or
  normal saline) solutions.
• There is no net movement of water either into or
  out of the cell.
• Cells maintain their normal shape.

WATCH VIDEO OF BLOOD IN AN ISOTONIC SOLUTION
12
Isotonic Solution

• Osmosis Animations for isotonic, hypertonic, and
  hypotonic solutions

Isotonic The concentration of solutes in the
external solution is equal to the concentration
of solutes inside the cell.
Result Water moves equally in both directions
and the cell remains same size! (Dynamic
Equilibrium)
13
Cells in an isotonic solution

• isotonic solution-
• ( concentrations)
• the concentration of dissolved substances in the
  solution is the same as the concentration of
  dissolved substances inside the cell.

H2O
H2O
Water Molecule Dissolved Molecule
14
Cells in an isotonic solution

• water molecules move into and out of the cell at
  the same rate, and cells retain their normal
  shape.

H2O
H2O
Water Molecule Dissolved Molecule
15
Cells in an isotonic solution

• A plant cell has its normal shape and pressure in
  an isotonic solution.

16
Hypotonic Solution

• A hypotonic solution contains less solute (thus,
  more water) than the cytoplasm of the cells.
• The water will move into the cells resulting in
  the swelling and lysis of the cells. 

WATCH VIDEO OF CRENATED RBCs SUBJECTED TO A
HYPOTONIC SOLUTION
17
Hypotonic Solution

• Osmosis Animations for isotonic, hypertonic, and
  hypotonic solutions

Hypotonic The solution has a lower
concentration of solutes and a higher
concentration of water than inside the cell.
(Low solute High water)
Result Water moves from the solution to inside
the cell) Cell Swells and bursts open
(cytolysis)!
18
Lets take a closer look!

• http//www.coolschool.ca/lor/BI12/unit4/U04L06/rbc
  .html

19
Cells in a hypotonic solution

• hypotonic solution dilute solution thus low
  solute concentration
• In a hypotonic solution, water enters a cell by
  osmosis, causing the cell to swell.

H2O
H2O
Water Molecule Dissolved Molecule
20
Cells in a hypotonic solution

• Plant cells swell beyond their normal size as
  pressure increases. (plants prefer this it makes
  the leaves firm)

21
Hypertonic Solution

• A hypertonic solution is a solution that contains
  more (hyper) solutes than the cytoplasm of the
  cell.
• Has less water than the cell and
• water moves out of the cell.
• The cells shrink.

WATCH VIDEO OF NORMAL RBCs SUBJECTED TO A
HYPERTONIC SOLUTION
22
Hypertonic Solution

• Osmosis Animations for isotonic, hypertonic, and
  hypotonic solutions

Hypertonic The solution has a higher
concentration of solutes and a lower
concentration of water than inside the cell.
(High solute Low water)
shrinks
Result Water moves from inside the cell into
the solution Cell shrinks (Plasmolysis/crenatio
n)!
23
Cells in a hypertonic solution

• hypertonic solution
• concentrated solution, thus a high solute
  concentration
• In a hypertonic solution, water leaves a cell by
  osmosis, causing the cell to shrink

H2O
H2O
Water Molecule Dissolved Molecule
24
Cells in a hypertonic solution

• Plant cells lose pressure as the plasma membrane
  shrinks away from the cell wall. PLASMOLYSIS

25
Passive Transport

• When a cell uses no energy to move particles
  across a membrane passive transport occurs
• Particles go DOWN their concentration gradient.
• Diffusion osmosis are passive transport.

Plasma membrane
Concentration gradient
26
Passive Transport by proteins

• Passive transport of materials across the
  membrane using transport proteins is called
  facilitated diffusion.

Channel proteins
Plasma membrane
Concentration gradient
27
Passive Transport by proteins

• Some transport proteins, called channel proteins,
  form channels that allow specific molecules to
  flow through.

28
Active Transport

• active transport Movement of materials through a
  membrane against a concentration gradient and
  requires energy from the cell.

Cellular energy
Carrier proteins
Plasma membrane
Concentration gradient
Cellular energy
29
How active transport occurs

• a transport protein called a carrier protein
  first binds with a particle of the substance to
  be transported.
• Each type of carrier protein has a shape that
  fits a specific molecule or ion.

30
Transport of Large Particles

• Endocytosis is a process by which a cell
  surrounds and takes in material from its
  environment.
• The material is engulfed and enclosed by a
  portion of the cells plasma membrane.
• resulting vacuole with its contents moves to the
  inside of the cell
• Exocytosis is the expulsion or secretion of
  materials from a cell.

Endocytosis
Exocytose
31
Study the diagram below.Which arrow shows the
direction the solute molecules would move to
achieve homeostasis?
32
If the membrane shown is permeable to molecules
of X, but impermeable to molecules of Y, what
will be the result of diffusion over time?

• Molecules of X on each side of the membrane will
  become equal in concentration.
• Molecules of Y on each side of the membrane will
  become equal in concentration.
• Molecules of X will increase in
• concentration on the right side.
• Molecules of Y will increase in
• concentration on the right side.

33
Cellular Transport Osmosis
34
What type of solution are these cells in?
C
B
A
Hypertonic
Isotonic
Hypotonic
35
Summary

• What is osmosis?
• Is osmosis considered passive or active
  transport?
• What are the 3 types of solutions involved in
  osmosis?
• 1.
• 2.
• 3.

36
How well did you do today?

• What is Osmosis?
• The movement of molecules.
• The movement of molecules from an area of high
  concentration to low concentration.
• The movement of water from a low concentration
  to a high concentration.
• The movement of water from a high concentration
  to a low concentration.