CONCEPT 2: ANALYZING THE
STRUCTURE AND FUNCTION
OF THE CELL MEMBRANE
Chapter 7 in Campbell
Pg. 53-58, 294-296 in Holtzclaw
Practice Questions: #1-12, p 70-71; #1, 4, 6 p. 74/75;
1-2 p. 296 Holtz
All Concept Checkpoints (Ch 7), #1-9 p. 141 Campbell
TRY THIS!
Which molecular movements are due to diffusion
or osmosis?
A. Ten minutes after a perfume bottle is dropped
in a room, a person can smell the scent in the
opposite corner of the room.
B. Oxygen moves from an alveolus into a capillary
within the lung.
C. When a plant cell is placed in salt water, water
moves out of the central vacuole of the cell.
D. When a cell is placed in a solution that is
hypotonic to the cell contents, water moves into
the cell through an aquaporin channel.

TRY THIS!
Which molecular movements are due to diffusion
or osmosis?
a.Ten minutes after a perfume bottle is dropped in
a room, a person can smell the scent in the
opposite corner of the room.
b.Oxygen moves from an alveolus into a capillary
within the lung.
c. When a plant cell is placed in salt water, water
moves out of the central vacuole of the cell.
d.When a cell is placed in a solution that is
hypotonic to the cell contents, water moves into
the cell through an aquaporin channel.

ANALYZING THE STRUCTURE AND
FUNCTION OF THE CELL MEMBRANE

You must know:
Why membranes are selectively permeable.
 The role of phospholipids, proteins, and
carbohydrates in membranes.
 How water will move if a cell is placed in an
isotonic, hypertonic, or hypotonic solution and
be able to predict the effect of different environments
on the organism
 How electrical gradients are
formed and their function in cells

WHY ARE MEMBRANES
SELECTIVELY PERMEABLE?

Cell (plasma) membranes allow some substances
to cross more easily than others
Fundamental to Life!
 Selectivity is due to the chemistry of the
phospholipid bilayer and embedded proteins

What is the role of phospholipids, proteins, and
carbohydrates in membranes?

Phospholipids
What is the role of phospholipids, proteins, and
carbohydrates in membranes?

Proteins
Globular shape!
 Primary, secondary, tertiary (and sometimes
quaternary) level of structure
 Shape determines function

What is the role of phospholipids, proteins, and
carbohydrates in membranes?

Proteins

are embedded in the phospholipid bilayer with their
hydrophophic and hydrophilic regions
What is the role of phospholipids, proteins, and
carbohydrates in membranes?

Proteins


are embedded in the phospholipid bilayer with their
hydrophophic and hydrophilic regions
AP Theme: Science as a Process
What is the role of phospholipids, proteins, and
carbohydrates in membranes?

Proteins


Move sideways within the plane of the phospholipid
bilayer
Science in ACTION
What is the role of phospholipids, proteins, and
carbohydrates in membranes?

Proteins

Many
different
functions
What is the role of phospholipids, proteins, and
carbohydrates in membranes?

Carbohydrates
Used for cell-to-cell signalling
 Can be attached to phospholipids: GLYCOLIPIDS
 Can be attached to proteins: GLYCOPROTEINS

What is the role of phospholipids, proteins, and
carbohydrates in membranes?

Carbohydrates

Attachment to
lipids or
proteins
HOW WATER WILL MOVE IF A CELL IS PLACED IN
AN ISOTONIC, HYPERTONIC, OR HYPOTONIC
SOLUTION?

You need to know the following terms:







Diffusion
Osmosis
Facilitated diffusion
Concentration gradient
Isotonic solution
Hypertonic solution
Hypotonic solution
ACTIVITY!
Observing Osmosis
WHAT DO YOU THINK OF THESE
QUESTIONS?
Identify each statement as TRUE or FALSE.
a.If a dead cell is placed in a solution hypotonic to
the cell contents, osmosis will not occur.
b.When two solutions separated by a selectively
permeable membrane reach osmotic equilibrium,
water molecules no longer move between the
solutions.
c. The rate of osmosis increases with increasing
differences in solute concentrations between two
solutions separated by a selectively permeable
membrane.
d.Osmosis is due to diffusion of water molecules
across a selectively permeable membrane.
WHAT DO YOU THINK OF THESE
QUESTIONS?
Identify each statement as TRUE or FALSE.
a.If a dead cell is placed in a solution hypotonic to
the cell contents, osmosis will not occur. False
b.When two solutions separated by a selectively
permeable membrane reach osmotic equilibrium,
water molecules no longer move between the
solutions. False
c. The rate of osmosis increases with increasing
differences in solute concentrations between two
solutions separated by a selectively permeable
membrane. True
d.Osmosis is due to diffusion of water molecules
across a selectively permeable membrane. True
WHAT DO YOU THINK OF THESE
QUESTIONS?
Are these statements correct or incorrect?
1. Osmosis can take place if a dead cell is placed in
a solution hypotonic to the cell contents.
2.Water movement into a cell through aquaporin
channels requires energy investment by the cell.
3.A solution of distilled water is hypotonic.
4.Diffusion is due to random movements of
molecules.
WHAT DO YOU THINK OF THESE
QUESTIONS?
1. Osmosis can take place if a dead cell is placed in a
solution hypotonic to the cell contents. Correct
2. Water movement into a cell through aquaporin
channels requires energy investment by the cell.
 Incorrect – Water moves into a cell through aquaporin
channels by diffusion, which does not require energy
investment by the cell.
3. A solution of distilled water is hypotonic.
 Incorrect – A solution of distilled water is hypotonic to
water containing solute molecules.
4. Diffusion is due to random movements of molecules.
Correct
Read Ahead - How electrical gradients
are formed?

You need to know the following terms:








Active transport
Sodium-potassium pump
Membrane potential
Electrochemical gradient
Electrogenic pump
Cotransport
Exocytosis
Endocytosis
Phagocytosis
 Pinocytosis
 Receptor-mediated endocytosis
