Transcript Cell Boundaries

Cell Boundaries
How is a window screen like a
cell membrane?

What are some things that can pass
through a window screen?

What are some things that cannot?

Why is it important for a cell membrane to
regulate what moves into and out of a
cell?
PSRs
Prefixes, Suffixes, Roots
Cyto – cell
Hyper – above
Iso – equal
Phag – eat
Semi – half
Endo – within/inside
Hypo – beneith
Trans – across
Exo – outside
Per – through/beyond
Write these PSRs in your journal
Cell Borders

Cell Membrane (semi-permeable)
Controls what enters and leaves cell.
made of Phospholipid bilayer
2 layers of phospholipids with a “mosaic” of
proteins and carbs. (In ALL cells!)

Cell Wall – (in plants)
Provides support and protection.
made of cellulose – a tough carb.
2 Ways to Cross the Membrane

Passive Transport – NO energy is
required to move a substance across the
membrane (moves along gradient)

Active Transport – Energy IS
REQUIRED to move a substance across
the membrane (moves against gradient)
Passive Transport - Diffusion

Diffusion - movement of particles from
areas of high concentration of solute to areas
of low concentration of solute.
 What
is concentration? What is a solute?

When the concentration is the same
throughout, equilibrium is reached.

Temperature and size of molecule affect the
rate of diffusion.
Diffusion Animation
Passive Transport - Osmosis

Osmosis – the diffusion of water particles
across a membrane.

Water moves from low solute to high
solute.

Why is osmosis important for cells?
Animated demonstration
How Osmosis Works in the Cell

Isotonic – Concentration of solutes
outside and inside cell are equal.
– water moves in and out at
the same rate
 Equilibrium

Hypertonic - Concentration of solutes
outside is higher than inside the cell.
 Water

out
Hypotonic - Concentration of solutes
outside is lower than it is inside the cell.
 Water
in
1. Animated Review of Hypertonic, Hypotonic and
Isotonic Solutions
What type of solution are these cells in?
A
Hypertonic
B
Isotonic
C
Hypotonic
Passive Transport:
Facilitated Diffusion

Facilitated Diffusion – Large molecules
(like glucose) move across the membrane
with the help of protein channels.

Moves from high concentration of
molecules to low – no energy required.
Diffusion / Passive Transport
Active Transport = ATP
Active Transport

Larger molecules (sugar) and ions (Na+,
K+, Ca+2) pass across the membrane
using proteins using ENERGY.

Substances move from low to high
concentrations.
Active Transport:
Exocytosis and Endocytosis
 Exocytosis
- Wastes and products are
packaged in vesicle by the Golgi and sent
OUT of cell
 Endocytosis
– cell membrane forms
vesicle and brings things INTO the cell.
7. TRANSPORT of LARGE
PARTICLES
WATCH VIDEO OF ENDOCYTOSIS, FORMATION OF FOOD VACUOLES OF PARAMECIUM
 Endocytosis (Endo = In):
cell surrounds and takes in
material from environment. Material does not pass through the
membrane; instead, it is engulfed and closed by a portion of
membrane and cytoplasm.
 Pinocytosis: water
 Phagocytosis: food/ minerals/
large particles
 Exocytosis (Exo = Out):
transport of materials out of cell
across cell membrane.
WATCH VIDEO OF EXOCYTOSIS, SECRETION OF FOOD VACUOLES FROM PARAMECIUM
Exocytosis
secreted
material
(extracellular fluid)
plasma membrane
plasma membrane
2
3
1
vesicle
(cytoplasm)
0.2 micrometer
Types of Endocytosis
– engulfs by surrounding
membrane around solids.
 Phagocytosis

“Phago-” means “to eat”
– pinches membrane and
brings in liquids.
 Pinocytosis

“Pino-” think “to pinch”
(a)
pinocytosis
(extracellular fluid)
Click on Active Transport, watch the
brief overview of Active Transport and
then click on Endocytosis in the bar
below the animation
1
2
Animated Review of Phagocytosis,
Pinocytosis and Receptor Mediated
Endocytosis.
3
vesicle containing
extracellular
fluid
(cytoplasm)
cell
(b)
phagocytosis
food particle
pseudopod
1
2
3
particle
enclosed in vesicle