A. UNDERSTANDING THE DEFINITION OF CELLS
Cells are the structural and functional unit of life
in the smallest constituent levels of organization of life. Cells word comes
from the Greek, the "cellula" or "cella" which means empty
space. The body of an organism composed of organ systems, organ systems drawn
up by the organ, organ established by the tissues, and the tissues formed from
the cells. Essentially every living being has cells that become the basic
constituent of their bodies. Cells organize and process all the information so
that it can perform the function of life in living beings. Based on the number
of their cells, living beings that are composed by many cells called
multicellular organisms, whereas living things that are composed by a single
cell called a unicellular organism.
 |
| THE CELL |
B. THE FUNCTION OF CELLS
As we have explained above that the cell is a
regulator and controller of all the activities of living bodies, either
consciously or unconsciously. This function is carried out not only by a single
cell, but a group of cells that make up the tissues, then the tissues with a
common goal will form organs, and some organs form organ systems and organ
systems form living things (organisms). Robert Hooke was the first scientist to
observe cells (by accident), he observed the cells of the cork oak plants under
the microscope and then found the empty cavities like honeycomb, which then
called the cell. In general, cell function as well as cell theory are :
- Cell as a functional unit of the body (The theory put forward by Max Schultze)
- Cell as a structural unit of the body (The theory put forward by Mathias Jacob Schleiden and Theodor Schwaan)
- As a unit cell growth and development of living things (Rudolf Virchow)
- Cells as a unit of heredity (inheritance) that can lower nature to their child (This theory was introduced by Walter Sutton and Theodor Boveri)
C. THE STRUCTURE AND PARTS OF A CELL
Cell consists of three main parts ; the cell
membrane, cytoplasm, and nucleus. Cells also have a solid component in the cytoplasm
of cells called organelles. Organelles have their respective functions.
 |
| CELL STRUCTURE |
1. Cell
Membrane
The cell membrane is a thin membrane which is the
outermost part of the cell, the cell membrane is also called plasmalemma. The
cell membrane is the part that controls the relationship between the components
of the cell with the environment outside the cell. The cell membrane is
composed of lipids (fats) in the form of phospholipids, proteins, and
carbohydrates with different compositions depending on the type of cell. As the
name implies, phospholipids (fatty compounds) prepared by phosphate that is
hydrophilic (water loving) and hydrophobic lipid (fear of water).
The cell membrane phospholipids are prepared by each
pair (fat) that is also called lipid bilayer. The protein is a cell membrane
protein possessed extrinsic (peripheral) and intrinsic proteins (integral).
Extrinsic Proteins (peripheral) is a protein that is attached to the outer
layer of the membrane, and the intrinsic proteins (integral) is a protein that
penetrates the membrane. The bond between extrinsic phospholipid and protein
will form a membrane called lipoproteins. The cell membrane can have a
semipermeable properties that are easily bypassed by the various components,
can also be selectively permeable which means it can only be passed by certain
ions.
Some of the function of this membrane are :
- Protect and wrap the cell contents.
- Separating and control relationships within the cell to the outside environments.
- The exchange or transport of the substance out of the cell, or vice versa.
- The scene of a chemical reaction.
2. The
cytoplasm (Fluid Cells)
Cytoplasm is a matrix cell between cell membrane and
nucleus. The main constituent of the cytoplasm is water which serves as a solvent
and the scene foro chemical reaction. Cytoplasmic matrix is cytosol (liquid)
which is colloidal (form a mixture that consists of two homogeneous
substances). Cytoplasmic matrix can change from gels (semisolid) to sol (liquid).
Cytoplasmic matrix is irritable (sensitive to stimulation) and conductable
(capable of transferring or forwarding stimulation).
Some functions of the cell's cytoplasm are:
- Venue for the chemical reactions and metabolism.
- As a point of keeping the function of the cell.
- Keeping the state in the cell.
- Arranging the transport of substances within the cell.
- The formation of energy.
- Controls the movement of cells.
The functions performed by the cell organelles. As we
have explained previously that in the cytoplasm are solid components called
organelles which have special functions of each. This Organelles function is to
support the life of the cell. Some cell organelles such as:
- Mitochondria, function to produce energy.
- Lysosomes, functional site of protein synthesis.
- Ribosomes, for performing digestion in the cell.
- Endoplasmic reticulum, serves to transport various substances in the cells.
- Golgi apparatus, for protein synthesis and is associated with the work of ribosomes and endoplasmic reticulum, protect and preserve the shape of the cell.
- Microfilaments, play a role in the process of cell movement.
- Chloroplasts, serves as the venue for photosynthesis in plants.
- Centrosome (centrioles), as a cell division.
- and others.
3. Cell
Nucleus (Nucleus)
The cell nucleus is the part that is generally round
or oval and are often located in the center of the cell or at the cell edge.
Nuclei are the most important part of the life of the cell. Nuclei has a
primary function as the central control of all cell activity. The cell nucleus
is protected by a wall that resembles the cell membrane. This protective
structure called the nuclear membrane.
There are some parts of the nucleus, namely:
a. Nucleoli
(Children Core)
Nucleoli are round-shaped structure composed by
filaments and granules components. Nucleoli contains RNA, DNA and proteins that
have the function to keep the assembly of ribosomes.
In general, the function of the Nucleoli are:
- As a central regulator and controller of all cell activity.
- Storage of genetic information of the organism.
- Starting and ending an action taken by the cell.
- The scene for most of the process of cell division.
b. Nucleoplasm
(Liquid Core)
Nucleoplasm is a viscous liquid resembling a jelly
that contains proteins, ions, enzymes and other components. Nucleoplasm has a
complex structure and function due to their much components.
c. chromatin
Chromatin is a string of fine threads contained in
the cell nucleus. Chromatin containing DNA, which are substances that store all
genetic information of an organism. When Cell deviding, the chromatin will
shorten, thicken and form a circular chromosome.
