Transport Mechanism in Cells

1. TRANSPORT
MECHANISM
IN CELLS
Prepared by: Ma’am Ronna Mae F.
Farinas

2. Introduction
Cells communicate with one another by
transmitting and receiving signals that can
cause changes in cellular behaviour. In this
chapter, we will describe the various modes of
transport that occur across cell membranes, the
many forms of connections that form between
cells, and the ways in which cells send and
receive signals.

3. Transport Across
Membranes

4. What is cell transport?
 Cellular transport is the process of movement of
substance across the cell membrane either into or out of
the cell.
 Cell membrane is a phospholipid bilayer that regulates
the entry and exit of molecules.
 Plasma membrane of cells defines the boundary of the
cell. Materials can enter and exit the cell if only the
plasma membrane allows it; in other words, the plasma
membrane is selectively permeable.

5. Phospholipid Bilayer
The plasma membrane is
composed mainly of
phospholipids, which consist of
fatty acids and alcohol. The
phospholipids in the plasma
membrane are arrange in two
layer, called a phospholipid
bilayer, with a hydrophobic, or
water-hating, interior and a
hydrophilic or water- loving
exterior.

6. Nevertheless, the two major factors
determine whether a molecule can cross
the plasma membrane are (1) size, smaller
molecules cross more easily than larger
ones (2) attraction to water: hydrophobic
(nonpolar) molecules cross more easily
than hydrophilic (polar) molecules.

7. Active Transport- requires energy
02
01
Two Basic Ways that Substances can Across the Plasma
Membrane
Passive Transport- requires no energy

8. Passive Transport
It occurs when substances cross the plasma
membrane without any input of energy from
the cell. Can only occur if the molecules
moving in and out of the cell are small,
uncharged and move from an area of high
concentration to an area of low concentration.

9. There are two types of Passive Transport
1. Diffusion
Simple Diffusion
 Movement of particles from an
area of higher concentration to
an area of lower concentration
until an equilibrium is
established.
 Doesn’t require energy.

10. There are two types of Passive Transport
Facilitated Diffusion
 Will still only occur if
concentration is higher on
one side of the membrane
than the other. It also
occurs when molecules
diffuse across membranes
with the help of transport
proteins.

11. Two Types of Transport Proteins Help with
Diffusion
1. Channel Proteins- Build the walls of the straw, creating an
open tunnel down the middle of the protein. Some channel
proteins remain open all the time, while others, known as
gated channel, open and close in response to signals.
2. Carrier proteins- When the right molecule binds to the
carrier protein, the protein changes shape and moves the
molecule to the other side of the membrane.

12. 2. Osmosis
 When the water molecules move from low
solute concentration to high solute or low
water concentration across a membrane
that is not permeable to the solute.
Examples: Red Blood Cells Placed into Freshwater

13. Hypertonic Solution
A solution that has a higher
solute concentration than
another solution. Water
particles will move out of
the cell causing crenation.

14. Isotonic Solution
A solution that has the same
solute concentration as
another solution. There is no
net movement of water
particles and the overall
concentration on both sides
of the cell membrane
remains constant.

15. Hypotonic Solution
A solution that has a lower
solute concentration than
another solution. Water
particles will move into the
cell, causing the cell to
expand and eventually lyse.

16. Prefixes mean
Iso- Equal
Hyper- High
Hypo- Low

18. Active Transport
The passing of molecules across a membrane
against the concentration gradient. It requires
energy. Small molecules are transported by
pumps and larger molecules are transported
by endocytosis.

19. Endocytosis
It is the process of taking material into the
cell by means of forming a vesicle or
pockets of the cell membrane. It takes place
when the material into the cell and it forms
a vacuole in the cell. Large molecules of
food and whole cells can be taken this way.

20. Two types of Endocytosis
Phagocytosis
 Means “cell eating”
 An extension of cytoplasm surrounds a particle and
package it into a food vacuole
 Requires an enormous amount of energy.
Pinocytosis
 Means “cell drinking”
 Tiny pockets from along the cell membrane fill with
liquid and form vacuoles with in the cell.
 Requires enormous of amounts of energy.

21. Exocytosis
The process where cells release large
amount of materials. Vacuole surrounding
material fuses with the cell membrane,
forcing the contents out of the cell and also
it requires energy.
1.

22. References
 https://www.ck12.org/biology/cell-transport/lesson/Cell-Transport-Advanced-BIO-
ADV/?fbclid=IwAR0KvyKYT-rkpzohUrQaOElGq7bc7IuOL0LAzja-
9AgT1CliKVqPCPcBQ1s#:~:text=What%20is%20cell%20transport%3F,to%20cross%20the%20cell%20m
embrane
 https://bio.libretexts.org/Bookshelves/Human_Biology/Book%3A_Human_Biology_(Wakim_and_Grewal)/0
5%3A_Cells/5.04%3A_Plasma_Membrane?fbclid=IwAR0IZITFle64Sk9d-
8azTA1p8XNiDl554jsXUUpD9iKURjuDZzN2YkowU_Y
 https://bio.libretexts.org/Bookshelves/Human_Biology/Book%3A_Human_Biology_(Wakim_and_Grewal)/0
5%3A_Cells/5.07%3A_Cell_Transport?fbclid=IwAR3VLlAH2pLc_eFJSKRqpf5-
cfv1T5u_qVY9ndiy61MmIbhWPGRCvP9WBhI#:~:text=There%20are%20two%20basic%20ways,active%2
0transport%2C%20which%20requires%20energy
 https://bio.libretexts.org/Bookshelves/Introductory_and_General_Biology/Book%3A_General_Biology_(Bo
undless)/05%3A_Structure_and_Function_of_Plasma_Membranes/5.06%3A_Passive_Transport_-
_Diffusion?fbclid=IwAR35OxurupuI8xfDXanLFLEarb53PhIrnZ7sew5iOZ_LecmdGuBY3etoIDQ#:~:text=Dif
fusion%20is%20a%20passive%20process,of%20substances%20through%20the%20air

23. THANK YOU
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