#Oxaloacetate Etatecaolaxalo

1. Chapter
2:STRUCTURE OF
CELLS AND
ORGANELLES
Presentation By: Faridah Hashim
Rossharkina Gorisma
Wong Hui Jin
CELLULAR COMPONENTS OF TYPICAL
PLANT AND ANIMAL CELLS

2. CELL
MEMBRANE

3. WHAT IS CELL
MEMBRANE ???

4. A cell membrane is a general
term that refers to any
membrane found within a
cell.
The cell surface membrane
which encloses the contents
of the cell.
Also called plasma membrane

5. Singer and Nicolson’s fluid-
mosaic model.

6. Characteristics :
~A thin , flexible layer which forms the outer boundary of
a cell.
~Composed mainly of phospholipids and proteins.
~Semi-permeable
~The heads(hydrophilic).
The tails(hydrophobic).
~The structure is dynamic where each lipid molecule can
move within its own monolayer and so is each protein
unit.
~The fluidity of the membrane depends on the length of
the fatty acid chains .
~Cholesterol with its hydrophilic head and hydrophobic
tail fits neatly within the phospholipid layer.
~The proteins are embedded in the phospholipid layer like
mosaic,either in only one monolayer or span the bilayer.

7. WHAT THE FUNCTIONS
OF CELL MEMBRANE
???

8. Functions : ^_^
* Separates the contents of a cell from its external
environment.
*Regulates the movement of substance entering and
leaving the cell.
*Allows the exchange of nutrients respiratory gases and
waste product between the cell and its environment.
*Acts as receptor sites in recognising external stimuli such
as hormone and antigen molecules.
*Membranes allow compartmentalisation and division of
labour especially within membrane-bound organelles.

9. CELL WALL *_*

10. CHARACTERISTICS
->The cell wall is carbohydrate
layer of cellulose found outside
the plasma membrane of plants
cells.
->2 type of cell wall primary &
secondary cell wall.

11. CELL WALL ^_^

12. Primary Cell Wall 
=found in young cells and cells that not highly
differentiated.
=e.g:meristem,parenchyme & collenchyme.
# thin layer found just outside the plasma membrane of
most plant cells.Also found on the outer layer of cells with
2nd cell wall.
#it consists randomly arranged microfibrils of cellulose in
an amorphous matrix.
#Each microfibril consists about 100 chains of cellulose
molecule of 5-20 µm and diameter of 1-2 µm.
#the matrix is made up of complex polysaccharides
(pectins and hemicellulose with long and branched
molecules)
#a middle lamella layer consists of magnesium and
calcium pectates for cementing adjacent cells.

13. #primary cell wall is porous.
-enables water to be transported apoplastically along it.
#Elastic and strong.
-enables parenchyma cells to become turgid and support
the whole plants especially in herbaceous plants.
#the wall is usually perforated with plasmodesmata for the
transport of substances between cells.

14. Secondary Cell Wall 
->is a harder and usually thicker layer cell
wall,formed between the plasma membrane and
primary cell wall.
1.The wall is made up of regularly arranged microfibrils or
bigger macrofibrils.The fibrils are arranged in layers parallel
rows,which are perpendicular to those of upper lower
layers.
2.The matrix in the 2nd wall is impregnated with
lignin,forming a hard and impervious layer.
3.The deposition of lignin in xylem vessels is not uniform
but in patterns like rings,helices or networks.

15. Fibrils arranged in layers of parallel rows.

16. Functions
#Maintains the shape of plant cells.
#Provide mechanical strength and support to plant
cells.
#Protects plants cells from bursting due to the movement
of excess water into the cells.
#cell wall of the xylem vessels forms empty tubes for water
transport from the roots to the leaves.
#provides food storage in the from hemicellulose in some
seeds.
#provides large surface area to volume ratio in root hair
cells where absorption can take place.
FUNCTIONS
*_*

17. Any Question ?