Passive Transport cont...
C. Facilitated diffusion
- Movement of molecules that can't easily
diffuse across membrane (too large, insoluble
in lipids)
- facilitated by carrier proteins
A. Slower than regular diffusion
B. Still no energy required
(going from high to low)
C. Ex. Glucose
How is a crossing guard like a carrier
protein?
Glucose binds to protein, changes shape
so it can cross hydrophobic interior, then
released
Types of Active Transport:
Basics:
- Movement of material up a concentration
gradient (requires energy input)
- Most energy needed is ATP
- Carried by Cell Membrane “Pumps” that
move material from low to high
concentrations
A. Sodium – Potassium Pump
1. Transports Sodium and Potassium against
their concentration gradients
a) 3 Na+ move out of the cell
b) 2 K+ move into the cell
c) This creates an electrical gradient (cell is
positively charged)
* Used in many things including creating
nerve impulses
Sodium – Potassium pump (see 2 K+ and
3 Na+ ions moving)
Active Transport cont.
B. Endocytosis and Exocytosis
1. Endocytosis – cells ingest macromolecules &
large particles
a) Can even be other cells
b) Cell membrane folds over the particle &
forms a vesicle
c) 2 types:
1. Pinocytosis – engulfing of small
solutes or fluids
(cellular drinking)
2. Phagocytosis – engulfing of big
particles (cellular eating)
Once particle has been engulfed, it will fuse
with a lysosome to digest it
* How body destroys harmful bacteria &
viruses
Which picture below shows pinocytosis
and which shows phagocytosis?
The dots are
liquids
B
A
How does Pac
Man feed?
2. Exocytosis – releases particles into
external environment
a) Used by the nervous system and
endocrine(glands) system
- releases hormones & molecules that
control activities of other cells
Exocytosis releases material outside of cell