Cellular Transport and the
Cell Cycle
Unit 3
Chapter 8
Different ways of transporting
materials across a cell membrane
1. Passive transport
1.
2.
3.
Diffusion
Osmosis: water diffusion
Facilitated transport
2. Active transport
3. Exocytosis
4. Endocytosis
Cells in isotonic solutions
 Cell loses and gains
water at an equal rate.
 Net change to cell =
nothing
Isotonic solution
 Not ideal for plant cells
because the cells
become flaccid (limp)
 Ideal for animal cells or
cells without cell walls
Cells in a hypotonic solution
 More water moves into
the cell than moves out.
 Net change = cell mass
increases
Hypotonic solution
 Ideal for plant cell
where the cell becomes
turgid (swollen)
 Not ideal for animal
cells where the cell
lyses (bursts)
Cells in a hypertonic solution
 More water moves out
of the cell than moves
in
 Net change = cell mass
decreases
Hypertonic solution
 Not ideal for any cell
 Both shrink.
Passive transport
 Movement of materials
across a cell membrane
in the direction of
higher concentration
to lower concentration
 No ATP energy
required
Passive transport by proteins
 Facilitated transport
 Movement of chemicals
down a chemical
gradient (from high to
low concentration)
through a protein
Passive transport
Channel vs. carrier proteins
Click
on
image
to
view
video.
Active transport
 Requires energy to move substances across the
membrane against the concentration gradient
(from lower to higher concentration)
Click on image
to view video.
Exocytosis: transport of large particles
out of cell
Endocytosis: transport of large
particles inside of a cell
Cell reproduction: making new cells
by a process called cell division
 Cell cycle: sequence of
growth and division of a
cell
 Step 1: Interphase (G1,
S, G2)
 Step 2: Mitosis and
Cytokinesis (M)
Eukaryotic chromosome structure
 Double helix coiled and
twisted into a
condensed structure
 Bacterial DNA differs in
that it is circular and not
linear.
Step 1: Interphase
 Grows in size
 Copies DNA
 No visible DNA
 G1, S, G2 phases
Each chromosome makes a copy, and the two
resulting chromosomes are joined at the
centromere.
Step 2: Mitosis (nuclear division)
 Prophase
 Metaphase
 Anaphase
 Telophase
Prophase: spindle fibers extend,
nuclear membrane disintegrates,
chromosomes coil up and pair up
Metaphase: Meta means “middle”,
chromosomes aligned along the middle
Anaphase: chromosomes pulled apart
when spindle fibers become shorter
Telophase: two nucleus form at each
pole of the cell
Cytokinesis: forming two daughter
cells identical to the parent cell
 Animal cells:
cell pinches
down the
middle
 Plant cells:
cell plate
forms to make
new cell wall
Onion root tip showing phases of
mitosis
The cell cycle
Click on image to view video.