Transcript General Biology Chapter 4 Cellular Transport

General Biology
Chapter 4
Cellular Transport
Cells and Their Environment
Cellular Transports
Two Major Types
Passive Transport
– Diffusion
– Osmosis
– Facilitated Diffusion
Active Transport
– Sodium Potassium Pumps
– Endocytosis
– Exocytosis
CELL MEMBRANE
Membranes are selectively permeable and
allow only certain substances to move across
them.
The interior portion of a cell membrane forms a
nonpolar zone that prevents ions and most large
molecules from passing through the membrane.
Membranes have ion channel gates that close
the pores of some ion channels in response to
– Stretching of the cell membrane
– Change in electrical charge
– The binding of specific molecules to the channel
PASSIVE TRANSPORT
Passive Transport - requires NO ENERGY does
NOT use ATP to move molecules
– Diffusion = random dispersion of molecules from an
area of HIGH concentration to an area of LOW
concentration. (Molecules down the concentration
gradient)
– Osmosis = is the diffusion of WATER molecules from
an area of HIGH concentration to an area of LOW
concentration (water down the concentration gradient)
– Facilitated Diffusion = Uses CARRIER PROTEINS to
transport specific subs. (sugar/amino acids) down a
concentration gradient.
Diffusion-PASSIVE
As a result of diffusion, the concentration of
many types of substances eventually become
balanced on both sides of a membrane.
Dispersal of ink or sugar in a beaker of water is
an example of diffusion.
Cell does not expend energy (no energy used)
Substances always flow from an are of high
concentration to an area of LOW concentration.
Facilitated Diffusion-PASSIVE
Use of transport proteins called carrier
proteins that bind to a specific subs. Carry
the subs. across the membrane and then
release the subs.
Amino acids and Sugars cross the
membrane in this manner
NO energy is required to transport the
subs.
OSMOSIS-PASSIVE
Diffusion of WATER into or out of a cell
Is a type of PASSIVE transport.
Diffusion of water down the concentration
gradient. (from HIGH to LOW)
Three water concentrations.
– Hypertonic
– Hypotonic
– Isotonic
PASSIVE- Hypertonic
A solution that causes a cell to shrink
More solute than water
If a cell is placed into a hypertonic solution
water will flow out of the cell
When a plant cell shrinks it loses Turgor
pressure.
A strong salt solution = hypertonic
solution/more salt than water. Therefore
the cell would shrink.
PASSIVE -Hypotonic
When water diffuses into the cell and the
cell swells.
If a cell is placed into a hypotonic solution
the cell will swell and may burst.
When the concentration of water
molecules is higher outside a cell than
inside the cell, water will diffuse into the
cell
PASSIVE -ISOTONIC
No net water movement.
Water diffuses into and out of the cell at
the same rate.
Fluid inside and outside is the same.
The cell stays the same – equilibrium
ACTIVE TRANSPORT
USES ENERGY USES ATP
Moves against the concentration gradient.
Moves molecules from an area of LOW to
HIGH concentration
Energy is required to move a substance
across a cell membrane
Unlike passive active REQUIRES
ENERGY
ACTIVE TRANSPORT
Three types
Sodium Potassium Pumps
Endocytosis
Exocytosis
Cell will use energy supplied by
ATP
ENDOCYTOSIS-ACTIVE
Transports molecules that are to large to be
moved through the membrane can be
transported into the cell by Endocytosis
Requires Energy to carry out Endocytosis.
Usually supplied by ATP
Endocytosis is a process that uses vesicles to
capture substances and bring them into the cell
Endocytosis the cell membrane extends to
engulf substances that are too big to pass
through the cell membrane
EXOCYTOSIS - ACTIVE
Ridding the cell of materials by
discharging the materials in vesicles
Helps rid the cell of waste
Molecules that are to large to be moved
across the cell membrane can be removed
by Exocytosis
Exocytosis requires ENERGY to expel
proteins and other materials from the cell
Paramecium
Unicellular aquatic organisms
Paramecia are aquatic (live in water) unicellular protists.
They have a number of characteristics also found in
animals
–
–
–
–
Need to ingest food in order to obtain energy (Heterotrophs)
NO cell wall.
Surrounded by a cell membrane
Have some of the same organelles as animals (
nucleus/mitochondria/ribosomes/cilia)
– In addition – paramecium have CONTRACTILE VACUOLES
Contractile vacuoles expel excess water.
Contractile vacuoles are found in unicellular aquatic organisms.
Question A
How can you explain the
observed relationship between
the salt concentration and the rate
of contractile vacuole
concentration?
Answer A
When there is less salt there is
more water causing the
contractile vacuoles pump faster.
Question B
If something happened to a
paramecium that caused its
contractile vacuole to stop
contracting, what would you
expect to happen?
Answer B
The water would build up inside
the paramecium causing it to
swell and then burst resulting in
death.
Question C
Would this result occur more quickly if
the paramecium was in water with a
high salt concentration or in water
with a low salt concentration? Why?
Answer C
LOW concentration Because if
the salt content is low then the
water content is high and water
accumulates more rapidly.
Homework
Pp. 88
#’s 1-6; 8; 10
Pp 89
#’s 1-3; 5 & 6
Define Key Terms pp. 87
Pp. 80 Section 1 Review #’s 4 & 5
Pp. 86 Section 2 Review # 6