Download 7.4 Cellular Transport Cellular Structure and Function

7.4 – Cellular Transport
Remember from 7.2…..
• Selective Permeability – substances do
NOT enter the cell indiscriminately.
– Nonpolar molecules tend to cross membrane
easily
– Polar molecules (water, glucose) cross
membrane slowly
Chapter 7
Cellular Structure and Function
7.4 Cellular Transport
Passive Transport
 Movement of particles across the cell
membrane without using energy
Three Modes of Passive Transport
 Diffusion
 Facilitated Diffusion
 Osmosis
Chapter 7
Cellular Structure and Function
7.4 Cellular Transport
Diffusion
 Movement of particles from an area of high
concentration to an area of lower
concentration
 Tendency to spread evenly through space
Starting
Conditions
Diffusion
Low
High
High
Low
Chapter 7
Cellular Structure and Function
7.4 Cellular Transport
 Diffusion is controlled by:
 Temperature
 Pressure
 Concentration
Dynamic Equilibrium
 Reached when diffusion of material into the
cell equals diffusion of material out of the
cell
 Molecules continue to move, but the
concentrations of molecule on both sides
stays the same.
DIFFUSION DEMO
MOLECULES FROM THE SPRAY ARE HIGHLY
CONCENTRATED CLOSEST TO ME. OVER TIME, THEY
WILL DIFFUSE THROUGH THE AIR TO THE BACK OF
THE ROOM.
Chapter 7
Cellular Structure and Function
7.4 Cellular Transport
Facilitated Diffusion - Still no energy needed
 Movement of materials across the plasma
membrane using transport proteins
Two main types of
proteins used =
Carrier proteins and
Channel Proteins
Chapter 7
Cellular Structure and Function
7.4 Cellular Transport
Channel Proteins
Carrier Proteins
Channel Proteins – a hollow protein that spans the width of the cell membrane and
acts as a tunnel for small particles.
Carrier Proteins - A protein that transports specific substance through intracellular
compartments, into the extracellular fluid, or across the cell membrane.
Chapter 7
Cellular Structure and Function
7.4 Cellular Transport
Osmosis
 Diffusion of water across a selectively
permeable membrane
Three Types of Solutions
 Isotonic
 Hypotonic
 Hypertonic
Osmosis
• Water always moves from an area of LOW
solute concentration to an area of HIGH
solute concentration.
OR
• From an area of HIGH water to an area of
LOW water
LEFT SIDE = 15 Sugar Molecules
10 H2O Molecules
Ratio = 1.5 Sugar per H2O
RIGHT SIDE = 3 Sugar Molecules
27 H2O Molecules
Ratio = 0.1 Sugar per H2O
LEFT SIDE = 15 Sugar Molecules
23 H2O Molecules
Ratio = 0.65 Sugar per H2O
RIGHT SIDE = 3 Sugar Molecules
14 H2O Molecules
Ratio = 0.2 Sugar per H2O
Eventually, both sides of the partially permeable membrane will have equal
concentration of sugar and water molecules.
Osmosis in Plant and Animal
Cells….
• Tonicity – ability of a cell to gain or lose
water
• Three types:
– Isotonic
– Hypertonic
– Hypotonic
• In plant cells, the cell wall makes sure only
so much water is allowed to enter the cell.
The wall maintains balance.
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
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
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