Lesson #3.4-Active Transport
NOT going with the
flow…
• Since some molecules are NOT able to
pass through the cell membrane (via
passive transport), another mechanism
is used to ensure the cell gets the
nutrients it needs
– This is called Active Transport
Active Transport
• Requires cellular energy
since substances are now moving
AGAINST the concentration gradient
(UPhill)
– From low to high concentration
• There are 2 main types:
1. Protein Carriers
2. Bulk Transport
1. Protein Carriers
• Uses transport proteins,
just like facilitated
diffusion
– BUT substance moves from low to high
concentration
• Energy is needed for this to happen
• Ex. Uptake of glucose by intestines
– A pump, using energy, forces more glucose
molecules to be absorbed into cells that
already have glucose
2. Bulk Transport
• Involves the movement of large
volumes of substances OR very large
molecules across the cell membrane
• The cell membrane changes shape and
actually wraps around the substance to
bring it into or out of the cell
2. Bulk Transport
• There are 2 types of bulk transport
A. Endocytosis
B. Exocytosis
A. Endocytosis
• Involves substances ENTERING the cell
• The cell engulfs material by wrapping
its membrane around it
– The membrane forms a small vesicle
around the substance, then “pinches” off
A. Endocytosis
• Next, the small vesicle fuses with a
lysosome (that is filled with enzymes)
– The lysosome digests the material inside
• There are 2 types of Endocytosis
i. Pinocytosis
ii. Phagocytosis
i. Pinocytosis
• Latin term for “Cell Drinking”
• Cell takes up large volumes of dissolved
or suspended molecules
– Ex. Intestinal cells take up fat droplets
ii. Phagocytosis
• Latin term for “Cell Eating”
• Cell engulfs large, solid particles
– Ex. WBC (which blood cells) “eat” bacteria
and viruses
B. Exocytosis
• Method by which large molecules and
large volumes of molecules exit the cell
• This is done by small vesicles breaking
off from Golgi Apparatus, fuse with the
cell membrane and then are released
out of the ell
– Ex. Insulin
hormone (protein)
is transported out
of pancreas cells
Video
• http://www.youtube.com/watch?v=kf
y92hdaAH0#t=105
• Adenine (nitrogenous base from DNA/RNA)
• Ribose sugar (found in RNA)
• 3 phosphate groups linked by high energy bonds
= Adenosine triphosphate (ATP)
Activity and Homework
• Read pages 56-58
• Answer questions on page 57 # 4-6
• Copy and answer questions on “Active
Transport Review” (next slide)
Active Transport Review
1. Which type of protein is involved in Active
Transport?
2. Describe the concentration gradient in the picture.
3. Why must cells use energy to move particles from a
region of lower concentration to a region of higher
concentration?
4. Describe the process of Active Transport (A.T).
5. What is the source of energy used in A.T?
6. How does the process of endocytosis differ from
the one show in the picture?
7. Why is endocytosis considered a type of A.T?
8. What process of A.T is the reverse of endocytosis?
Explain.