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| Plant cell |
Living organism exist in various organizations of life that
enable them to effectively perform the characteristics of living things. Every
living thing is made up of cell, which is
the basic structural and functional unit of protoplasm bounded by a membrane
and containing nuclear and cytoplasmic materials.
An organism with one cell, is said to be unicellular, while that with two or more cell is called multicellular organism.
The protoplasm consist
of the followings organelles,
1 - Endoplasmic reticulum(ER): This is an irregular network of branching and fusing membranous tubule with
many flattened sacs call cistenae.
The nature of this organelle varies with the function and physiological status
of the cell.
In cells that are involve in protein synthesis which are to
be used for secretion, a large part of the E.R is studded on the anterior
surface with ribosome attached to it
and are called rough or granular endoplasmic reticulum.
Other cells such as those involve in lipid synthesis does not
have ribosome attached to their E.R and are call Smooth endoplasmic reticulum.
Functions of
Endoplasmic reticulum
- Transport protein, lipid and other materials through the cell.
- Manufacture digestive enzymes and package them to the lysosomes.
- It’s the major site of cell membrane synthesis
2 - GOIGI APPARATUS: This is a network of flat tubule or vesicle located between the nucleus
and the secretory pole or surface of the cell.
Functions of Goigi apparatus
- Package materials and prepare them for secretion
- Growth of some fungi hypae occurs when goigi bodies contribute their content to the wall of the hypae tip.
- It modify proteins destined for different part of the body by adding specific group and sending them on their way to proper location, eg Lysosome proteins added phosphate added to their mannose sugar.
3 - LYSOSOME: These are roughly spherical
organelle enclosed in a single membrane, it is very important in cells that
obtain their nutrition by endocytosis
(ingestion of food articles by enclosing
them in vesicle or vacuole pinched of from the plasma membrane). Lysosome
is present in a variety of organisms – some algae, protozoan, fungi, including
plants and animals.
Functions of Lysosome
- Destroys worn out organelles after they have performed their function.
- Joins with phagosome for defends and food acquisition purposes
- Maintains acidic environment by pumping protons into their interior
- Involve in intracellular digestion and contains enzymes needed to digest all macro molecules.
4 - Ribosomes: Ribosome are tiny organelles found
embedded on rough endoplasmic reticulum or found free in cluster like form in
the cytoplasmic matrix. Eukaryotic
ribosome is larger than the bacteria 70s ribosome, and has a diameter of 60S
and 40S subunit. When bound to E.R. to form rough E,R, it is attached through
its 60S subunit.
Functions of Ribosome
- Ribosome is the site for protein synthesis
- Smooth or free ribosomes are the site of secretory and nonmembranous protein.
5 - Mitochondria: This is the power house of the cell;
it is where Tricarboxylic Acid Cycle (TAC) activities and generations of A.T.P
by electron transport and oxidative phosphorylation take place. This organelle
is bound by two membranes separated by an inner mitochondrial membrane.
Special infolding of the membrane call cistanae greatly increase it surface area.
Function of
Mitochondrion
- It is involve in energy production through the use of tricarboxylic acid cycle, electron transport, oxidative phosphorylation and other energy metabolic pathway.
6 - NUCLEUS: The nucleus is a membrane delineated spherical body and the most visually prominent organelle of a cell; it is not a membrane bound organelle. It was discovered by Robert Hook in 1839, to be the constant feature of eukaryotic cells.
The nucleus is the
repository of genetic information and the control center of the cell. The most
notable structure within the nucleus is the nucleolus; a nucleus may contain
one or more nuclei.
Functions of Nucleus
- It’s the control center of a cell
- Its involve in ribosome synthesis
- The nucleus houses genetic information.
7 - PLASMA MEMBRANE (Cell
membrane): Plasma
membrane is a membrane that separates the inside of a cell from its outside
environment.
It is a selective barrier….. that regulates the movement of
certain substances in and out of a cell. This cell structure keeps the
intracellular milieu constant and protects the cell from outside force.
Plasma membrane is
between 7.5 – 10n in thickness, and contains phospholipids such as
phosphatidylchloride (lecithin) and cephalin, which consist of two long non
polar (hydrophobic) hydrocarbon chains linked to a charged hydrophilic head
group.
Cholesterol is also found in the plasma membrane, it breaks
down the complex parking of a phospholipids chain, and this disruption makes
the membrane more fluid. The fluidity of the membrane is controlled by the
amount f cholesterol present.
Plasma membrane is also rich in protein about 50%w/w, which is
divided into integral proteins and peripheral proteins.
Integral proteins are directly incorporated within the lipid
bilayers and are distributed as globular proteins.
Functions of Plasma
membrane
- It regulates the passage of substances in and out of the cell, see also, EXCHANGE OF MATERIALS ACROSS PLASMA MEMBRANE
- It is the site of important biochemical reaction such as adhesion, recognition and hormonal responds.
- It protects cytoplasm from external forces.
8 - CHLOROPLAST: Plastids are cytoplasmic organelles
of algae and higher plants that often posses pigment such as chlorophylls and carotenoids, and are the site of synthesis and storage of food
reserves. The most important type of plastid is chloroplast.
Chloroplast contains chlorophyll and uses light to convert carbon
dioxide (CO2) and water (HO2),
to carbohydrate and Oxygen (O2), in a process call photosynthesis.
6CO2 + 6HO2 → C6H12O6 + 6O2.
Chloroplast has two membrane, Matrix and stroma, lies
within the inner membrane. It contains DNA, ribosomes, lipid droplets, starch
granuli and a complex internal membrane system whose most prominent components
are flattened membrane delineated sacs, the
thylakoids. The chloroplast of many algae contains pyrenoid, a dense region of protein surrounded by starch or
another polysaccharide. Pyrenoids are important in polysaccharide synthesis.
Function of Chloroplast
- Is the site of synthesis and storage of food reserves.
CELL WALL: The cell wall is the non living outer boundary of a cell, made of cellulose in plant but absent in animals.
Function of Cell wall
- Facilitates free passage of substances
- Provide rigidity to the cell and plant as a whole
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