The document summarizes key concepts about the plasma membrane and cell transport mechanisms. It defines the plasma membrane as a selectively permeable barrier that follows the fluid mosaic model. It then describes the main components of the plasma membrane - phospholipids, cholesterol, proteins, and carbohydrates. The document outlines different transport mechanisms including passive transport mechanisms like diffusion and osmosis, as well as active transport mechanisms like primary active transport and secondary active transport. It provides examples of transport proteins and discusses endocytosis and exocytosis.

1. Life at the Edge :
Prepared by:
MR. KEVIN FRANCIS E. MAGAOAY
Faculty, SHS Biology Department
C h a p t e r 7
Protecting the cell since forever

2. Learning Objectives:
 Describe the structural components of the plasma
membrane and relate the structure to its function
 Describe each transport mechanism
 Enumerate important materials that enter and exit
the cell and identify the transport mechanism used
to move them
 Define tonicity and its effects on cell

3. Overview:
 Review of the structure and components of the
plasma membrane
 Transport mechanism

4. Meet the Plasma Membrane

5. Plasma Membrane
 Follows a FLUID MOSAIC MODEL
 Selectively permeable
 A film only 8nm thin
 It would take around 8000 plasma membranes
to equal the thickness of a sheet of paper

6. Discovery of the Plasma Membrane
 The existence of plasma membrane was
discovered in 1890s and its chemical components
was discovered in 1915
 In 1935, Hugh Davson and James Danielli
theorize that the structure of plasma membrane
resembles a sandwich
 In 1972, Garth L. Nicolson proposed the Fluid
Mosaic Model

7. Components of the Plasma Membrane
Component Function
Phospholipid Main fabric of the membrane
Cholesterol Cell insulation
Protein Transport of substances through
membrane and cell recognition
Carbohydrates Cell recognition

8. Plasma Membrane

9. Phospholipid
 Composed of 3 carbon
glycerol backbone with two
fatty acid molecules
attached to carbon 1 and 2,
and a phosphate containing
group attached to the third
carbon
 Amphipathic, has
hydrophilic and hydrophobic
regions

10. Membrane Proteins
Integral Proteins
Penetrate the hydrophobic
core of the plasma
membrane
Many are transmembrane
that completely span the
plasma membrane

11. Membrane Proteins
Peripheral Proteins
Not imbedded in the
membrane at all
Found on the periphery or
on the sides of the
membrane

12. Membrane Carbohydrates
Glycolipids
Sugar chains covalently
bonded to lipids
Glycoproteins
Sugar chains covalently
bonded to proteins

13. Functions of Membrane Proteins
and Carbohydrates
Transport
 A protein that spans the
membrane may provide a
hydrophilic channel across the
membrane
Enzymatic Activity
 A protein built into the membrane
may be an enzyme with its active
site exposed to substances in
the adjacent solution

14. Functions of Membrane Proteins
and Carbohydrates
Signal Transduction
 A protein built into the membrane may
have a binding site with a specific
shape that fits the shape of a chemical
messenger, such as a hormone
Cell to Cell Recognition
 Some glycoproteins serve as
identification tags that are specifically
recognized be membrane proteins of
other cells

15. Functions of Membrane Proteins
and Carbohydrates
Intercellular Joining
 Membrane proteins of adjacent cells may
hook together in various kinds of
junctions such as gap junctions and tight
junctions
Attachment to the cytoskeleton/ECM
 Microfilaments or other elements of the
cytoskeleton may have noncovalent bind
to membrane proteins, a function that
help maintain cell shape

16. Classification of Transport Proteins
Uniporter
 Transports substances in a
unidirectional manner depending on
the concentration gradient
Symporter
 Transports different types of molecules
in the cell membrane at the same time
Antiporter
 Transport different types of molecules
in the cell membrane in opposite
direction at the same time

17. Cell Transport Mechanism
 Refer to the various ways by which different
substances can be allowed to enter the cell
 If the exchange of substances occur in the direction of the
concentration gradient, there is no need for energy output from
external factors
 If the exchange of substances occur against the direction of the
gradient, inputs of extra metabolic energy are required

18. Cell Transport Mechanism
Passive
Transport
Diffusion
Osmosis
Facilitated
Diffusion
Active Transport
Primary Active
Transport
Secondary Active
Transport
Bulk or Vesicular
Transport
Endocytosis and
Exocytosis
Phagocytosis
and Pinocytosis
Receptor-
mediated
endocytosis

19. Key Terms
Solute
Refers to the substance that needs to be
dissolved, catalyzed or broken down in order to be
utilized by the cell
Solvent
Refers to the substance that will dissolve the
solute such as water which is the versatile solvent

20. Key Terms
Concentration Gradient
Refers to how solute particles will move
through a gas or solution from an area with a
higher number of particles to one with a lower
number of particles while being separated by a
membrane

21. Passive Transport
 Movement of a substance across a membrane
with no energy investment
Passive Transport
Diffusion Osmosis
Facilitated
Transport

22. Diffusion
 Happens when particles
move from an area of
high concentration to an
area of low concentration

23. Factors that Affect Diffusion
 Extent of the concentration gradient
 Mass of the molecules diffusing
 Temperature
 Solvent density
 Solubility

24. Osmosis
 The diffusion of free water
across a selectively
permeable membrane
 The diffusion of solvent
from an area of lower
solute concentration to an
area of higher solute
concentration

25. Osmosis in Action
Tonicity
The ability of the surrounding solution to cause a cell
to loss or gain water

26. Osmosis in Action

27. Facilitated Transport

28. Active Transport
 Uses energy to move solutes against their
gradients
 To pump a solute across a membrane against its
gradient requires work, the cell must expand
energy
 Uses carrier protein

29. Active Transport

30. Primary Active Transport
 Binding of three Na ions to their active sites on
the pump which are bound to ATP
 ATP is hydrolyzed leading to phosphorylation of
the cytoplasmic side of the pump
 Phosphorylation is caused by the transfer of the
terminal group of ATP to the transport protein
making ATP become ADP

31. Secondary Active Transport
 Once the Na ions are liberated, the pump binds
two molecules of K to their respective binding
sites causing dephosphorylation of the pump
 Two K ions are transported into the cell

32. Endocytosis/Exocytosis

33. Phagocytosis

34. Pinocytosis

35. Receptor-Mediated Endocytosis