Download Plant cells Structure of the plant cells :

Plant cells
Structure of the plant cells :
Plant cell
The plant cell wall is thick, rigid, box like
It consists of cellulose fibrils encased in a cement
of polysaccharide and proteins .
Function:
1-protects cell membrane from mechanical or
osmotic rupture .
2-firmly fixes the position of the cell .
3-confirms physical shape and strength upon plant
tissues.
◦ bounds the outer nurface of the protoplost ( cytoplasm +
Vacuole )
◦ It made of lipid bilayer and proteins
peripheral
can be removed by
integral
deeply embedded
in the lipid biloyer
solution of high
ionic strength ( IM Nacl)
◦ .
◦ The cell membrane of a djacent cells
communicate through plasodesmata.
◦ The outer purface is covered with granules which
are responsible for synthesis of cellulose
microfibrils of the cell wall .
◦ It is selective in permeability .
◦ It contains active transport system
It is about 4-6 Mm in diameter .
It is surrounded by perinuclear envelope.
The DNA is combined with histones and
organized into chromosomes .
The nucleolus is rich in RNA .
Membrane surrounded organelles that contain
plastid those containing chlorophyll are called
chloroplasts. 5 Mm long
made of outer membrane, inner membrane with an
intervening intermembrane space.
The inner membrane surrounds structure called
soluble enzymes and membranous structure called
thylakoids which are flattened sacs .
A pile of these sacs is called a granum .
the thylakaid membrane contain the:
1. energy transducing machinery
2. light harvesting proteins
3. reaction centers
4. electron transport chains and
5.ATP synthetase.
The stroma contain soluble enzymes that
utilizes the NADPH and ATP synthesized by
the thylakaid to convert CO2 in to sugar
CO2 + NADPH +H+ +ATP
glucose
+NADP+ADP+PI
The thylakaid membrane is impermeable to
most molecules and ions .
The outer membrane is highly permeable to
small molecules and ions .
Chloroplasts contain their own DNA and the
machinery for replicating and expressing it .
chloroplasts are relatively forge compared to
mitochondria .
there may be one , several or many per cell .
They are the main source of energy of
photosynthetic cells in light with production
of oxygen .
It found in all plant cells .
made of outer membrane and inner membrane
which are different in lipid composition and
enzyme activity .
The inner membrane surrounds the matrix which
is rich in enzymes .
Mitochondria also contains specific type of DNA.
In non- photo synthetic cells mitochondrial
respiration is the main source of energy via
respiration .
they are characteristic of a plant cell .
They are small in young cell and greatly in
size with age .
often causing the cytoplasm to become
compressed against the cell wall.
They contain: 1. dissolved sugars 2. salts of
organic acids
3. proteins 4. mineral salts
5. pigments
6. oxygen
6.Co2
Contains digestive enzymes , that degrade
macromolecules, no longer useful to cell .
contains high conc of pigments ( in some plant )
deep purple to red colors to flowers , fruits .
Physical support to plant cell .
Store Flavanoids which attract insects to help
pollination .
Store large amounts of proteins called protein
bodies .
ER is composed of extensive network of
interconnected, membrane bound tubules
and vesicls which extend throughout the
cytoplasm .
some ports of ER membrane have ribsomes
referred as rough ER ( RER).
while other parts don't have ribosomes
referred as smooth ER (SER).
◦ Ribosomes are the site of protein synthesis .
◦ RER serves to channel protein products through .
◦ flattened single membrane vesicles .
◦ It functions in the secretion of cell products .
Single membrane structure , that contain oxidases
( oxidative enzymes ) responsible for
photorespiration
single membrane vesicles , that contain
hydrolytic enzymes .
Present in etiolated leaves ( leaves that turn
yellow ) and in primary leaves or cotyledons
of germinating seeds.
1313- chromoplast :
contain corotinoids, responsible for the color
of fruits & flower.
1414-Amyloplost :
filled with starch granules .
1515-Spherosomes :
present in lipid storing tissues. They
synthesize , store & mobilize lipids mostly in
the form of TAG .
Cylinders mode of globular protein
( Tubulin ) these are 3 Types in plants
◦ Microtubules form the nuclear
spindle during mitosis .
◦ Microtubules present in the
cytoplasm .
◦ Microtubules in flagella and cilia .
plants cell are of different types and are
divided into 2 main categories:
The First is responsible for performing all the
metabolic activities of the plants .
Responsible For other Functions either as
mechanical support or conduction of fluids