BOTANY COURSE
CELL
TRANSPORTATION

Cell

Cell Transport
Cell transport is the
movement of
substances across the
cell membrane either
into or out of the cell.

Cell Membrane
The cell membrane, also known
as the plasma membrane, is a
double layer of lipids and proteins
that surrounds a cell. It is a
selectively permeable barrier,
meaning it allows some substances
to cross, but not others. Like a
drawbridge intended to protect a
castle and keep out enemies, the
cell membrane only allows certain
molecules to enter or exit.

Phospholipids are lipid
molecules made up of
a phosphate group head
and two fatty acid tails. It
is a molecule that forms
the characteristic- double
layer of the plasma
membrane.
Phospholipid Bilayer

1.Passive Transport
•Simple Diffusion
• Facilitated Diffusion
•Osmosis
2.Active Transport
•Sodium-Potassium
Pump
•Endocytosis
•Exocytosis
Types of Cell Transport

What is Passive Transport?
Passive transport occurs
naturally, as substances move
down a concentration gradient in
the absence of energy. Therefore,
the primary difference in active
transport vs passive transport is
the energy requirement.

Types of Passive Transport
• Simple Diffusion
A process of diffusion
that occurs without the
aid of an integral
membrane protein.
Allows substances to
pass through cell
membranes without any
energy.
• Facilitated Diffusion
A process that occurs
when molecules or ions
pass through a cell
membrane with the
assistance of an
embedded transport
protein.

Types of Passive Transport
• Osmosis
Osmosis is when a substance
crosses a semipermeable
membrane in order to balance the
concentrations of another
substance. In biology, this is
usually when a solvent such as
water flows into or out of
a cell depending on the
concentration of a solute such as
salt.

Types of Osmosis
Solutions
• Hypotonic Solution
• Hypertonic
Solution
• Isotonic Solution

Types of Osmosis Solutions
• Hypotonic Solution
Hypotonic solution, there is a
higher concentration of solutes
inside the cell than outside the
cell. When this occurs, more
solvent will enter the cell than
leave it to balance out the
concentration of solute.
Example: Plant cells need more
water than animal cells.
• Hypertonic Solution
Hypertonic solution is the
opposite of a hypotonic
solution; there is more solute
outside the cell than inside it.
In this type of solution, more
solvent will exit the cell than
enter it in order to lower the
concentration of solute outside
the cell

Types of Osmosis Solutions
• Isotonic Solution
Isotonic solution has the same concentration
of solutes both inside and outside the cell. For
example, a cell with the same concentration of
salt inside it as in the surrounding water/fluid
would be said to be in an isotonic solution.
Under these conditions, there is no net
movement of solvent; in this case, the amount
of water entering and exiting the cell’s
membrane is equal.

•Hypotonic. •Hypertonic. •Isotonic

What is Active Transport?
Active transport moves
substances from a region of lower
concentration to a higher
concentration, i.e., against the
concentration gradient. There is an
energy requirement for this
process, as it does not occur
naturally in the absence of active
forces.

Types of Active Transport
• Sodium - Potassium Pump
The ability of the sodium-potassium
pump to transport potassium into cells
while transporting sodium out of cells
is so important that some estimates
suggest we spend a total of 20-25% of
all the energy we get from food just
performing this one task! In neurons, a
great majority of the cell’s energy is
used to power sodium-potassium
pumps.

Types of Active Transport
• Endocytosis
Endocytosis, a cell “eats” something
by wrapping and re-forming its
membrane around the substance or
item.
It then “pinches off” to form a small
sphere of membrane called
a vesicle that contains
the molecule and transports it to
wherever it will be used in the cell.

Types of Active Transport
• Exocytosis
Exocytosis, a cell moves something
outside of itself in large quantities by
wrapping it in a membrane called a
vesicle and “spitting out” the
vesicle. This most commonly occurs
when a cell wants to “export” an
important product, such as cells that
synthesize and export enzymes and
hormones that are needed throughout
the body.