Download The Plasma Membrane

The Plasma Membrane
The Gateway to the Cell
GPS
 SB1.
Students will analyze the
nature of the relationships between
structures and functions in living
cells.
– A. Explain the role of cell organelles for
both prokaryotic and eukaryotic cells,
including the cell membrane, in
maintaining homeostasis and cell
reproduction
– D. Explain the impact of water on life
processes (i.e., osmosis, diffusion)
Recall that
 The
process of maintaining balance
in an organism’s internal
environment is called---homeostasis!
 Essential to survival
 One of the primary structures for this
is the…
 PLASMA MEMBRANE!
Vocabulary
 Homeostasis
 Cell
or plasma membrane
 Semipermeable
 Phospholipid
 Hypo-, Hyper-, Isotonic
 Diffusion
– Passive
– Facilitated
 Active
transport
Phospholipids
Phospholipids have a hydrophilic end
and a hydrophobic end.
Hydrophilic = water loving
Hydrophobic = water hating
TAILS
HEAD
The Hydrophilic ends rotate outward
toward the water.
The Hydrophobic ends rotate inward
toward each other.
This makes a double layer of
phospholipids—phospholipid bilayer!
Structure of Cell Membrane
PHOSPHOLIPID 
PHOSPHOLIPID
BILAYER
Cell Membrane 
(CELL)
Chapter 7
Cellular Structure and Function
7.2 The Plasma Membrane
Selective Permeability
 The plasma membrane controls the movement of
substances into
and out of the cell.
Plasma Membrane
 Controls the amount of a
substance entering the cell
 Controls the amount of a
substance leaving the cell
Chapter 7
Cellular Structure and Function
7.2 The Plasma Membrane
Plasma Membrane
 Thin, flexible boundary between the
cell and its environment
 Allows nutrients into the cell
 Allows waste to leave the cell
Chapter 7
Cellular Structure and Function
7.2 The Plasma Membrane
 The plasma membrane is composed of the
phospholipid bilayer.
 A phospholipid molecule is composed of a glycerol
backbone, two fatty acid chains, and a phosphate
group.
This membrane got moves!
 Structure
is not fixed (like a
brick wall) but moves around
– called a fluid mosaic
Chapter 7
Cellular Structure and Function
7.2 The Plasma Membrane
Fluid Mosaic Model
 The phospholipid
bilayer allows other
molecules to “float”
in the membrane.
Other Components
 Proteins
 Cholesterol
 Carbohydrates
Membrane Proteins
Marker Proteins – like nametags to identify
the cell to other cells. Works with the
immune system
 Transport Proteins – Move materials into and
out of the cell
 Receptor Proteins – Allows the cell to interact
with other cells.

Protein Channel
Ok, recap!!!
 Selective
permeability allows the
membrane to control what enters and
leaves the cell
 Plasma membrane composed of 2
layers of phospholipid molecules
 Cholesterol and transport proteins aid
in function of membrane
 Fluid mosaic model describes it
Fill in the blanks
 The
axillary border of the scapula is
________ to the vertebral border.
 The hips are __________ to the
shoulders.
 The knee is ___________ to the
ankle.
 The cranium is __________ to the
scalp.
How important is the receptor in
a negative feedback system?
Sinoatrial (SA) node?
Name that quadrant.
?
Movement of Molecules Across the
Cell Membrane
 Passive
Transport – requires no
cellular energy
Active Transport – Requires cellular
energy
Types of Passive Transport
 Diffusion
–
– Molecules move with a Concentration
Gradient, from high concentration to low
concentration.
– Requires no energy
– Molecules continue to move until an
equilibrium is reached
Cellular Structure and Function
7.4 Cellular Transport
Diffusion in a Cell
Osmosis
The Diffusion of Water Across a
Selectively Permeable
Membrane
Osmotic Pressure Gradients
 In
general, water moves toward the
area with a higher solute
concentration because it has a lower
water concentration.
Hypertonic Solutions
 Contain
a higher concentration of
solute outside of the cell than inside
of the cell.
 When a cell is placed in a hypertonic
solution, the water diffuses out of the
cell, causing the cell to shrivel.
Chapter 7
Cellular Structure and Function
7.4 Cellular Transport
Hypertonic Solution
 Solute concentration is higher outside the
cell.
 Water diffuses out of the cell.
Plant Cell
Blood Cell
13,000x
Hypotonic Solutions
 Contain
a low concentration of solute
outside of the cell as compared to
inside of the cell.
 When a cell is placed in a hypotonic
solution, the water diffuses into the
cell, causing the cell to swell and
possibly explode.
Chapter 7
Cellular Structure and Function
7.4 Cellular Transport
Hypotonic Solution
 Solute concentration is higher inside the
cell.
 Water diffuses into the cell.
Plant Cell
Blood Cell
13,000x
Isotonic Solution
 The
concentration of solute inside of
the cell is equal the concentration of
solute outside of the cell. Therefore,
water move equal into and out of the
cell.
Chapter 7
Cellular Structure and Function
7.4 Cellular Transport
Isotonic Solution
 Water and dissolved substances diffuse
into and out of the cell at the same rate.
Plant Cell
Blood Cell
11,397x
Facilitated Diffusion
 Diffusion
with help!!
 Uses Transport Proteins to move
large molecule across the plasma
membrane
Molecules
move with the
concentration
gradient.
Downhill !!
Chapter
7
Cellular Structure and Function
7.4 Cellular Transport
Carrier Proteins
Channel Proteins
Active Transport
 Move
molecule against the
concentration gradient. Uphill!!
 Known as solute or ion pumps
Cellular Structure
and Function
7.4 Cellular
Transport
Active Transport
 Movement of particles across the cell
membrane using energy
Active Transport Using Carrier
Proteins
2 Special Types of Active Transport
 Endocytosis
- large molecules are
engulfed by cell.
– Phagocytosis – cell eats
– Pinocytosis – cell drinks
 Exocytosis
– large molecules are
removed from the cell.
Cellular Structure and Function
7.4 Cellular Transport
Endocytosis
 Process by which the
cell surrounds and
takes particles into
the cell
Exocytosis
 Secretion of material
out of the plasma
membrane