What is a cell?
Robert Hook(1665), an English scientist, He described the cork as composed of small spaces surrounded by firm wall and gave the name cells. after that In 1831 Robert Brown discovered the nucleus in the cell. therefore it is concluded that cell is a structural and functional unit of all living organism.
Cell and Its Organelle
Cells are the basic unit of life
1.
All
organisms are made up of one or more cells and the products of those cells.
2.
All
cells carry out life activities (require energy growth, have a limited size.)
3.
New
cells arise only from other living cells by the process of cell division.
Despite their
difference, they often share certain structures, these are referred to as
organelles.
CELL STRUCTURE
Three
main components of any plant/ animal cells.
1. Plasma Membrane / Cell Membrane:
Structure: A lipid membrane layer composed of
proteins and carbohydrates. It is fluid like.
Functions: The cell membrane separates the
cell from its external environment. It protects the cell and provides
stability.
In
order to transport materials, proteins are found embedded within the plasma membrane.
Carbohydrates are attached to proteins and
lipids on the outer lipid layer.
2. Cytoplasm:
Structure: The jelly like structure composed
of mainly water and found between the cell membrane and nucleus. The cytoplasm
makes up most of the body of a cell and is constantly streaming (flowing)
Function: Organelles are found here and
substances like salts may be dissolved in the cytoplasm.
3. Nucleus:
Structure:
The largest organelle in the cell. It is dark and round, and is surrounded by a
double membrane called the nuclear envelope / membrane. The nucleus contains
genetic information (DNA) on special strands called chromosomes.
Functions:
The nucleus is the “control centre” of the cell for cell metabolism and
reproduction.
Organelles are found in both plant
and animal cells
1.
Endoplasmic
Reticulum (ER): ER is made of Cisternae. The ER is a network of membranous canals filled with fluid.
They Carly materials throughout the cell. The ER is the “Transport System” of
the cell.
- There
are two types of ER.
a. Rough ER: It is lined with ribosomes
and is rough in appearance.
b. Smooth
ER: It is contains no ribosomes and is smooth in appearance.
2.
Ribosomes:
Ribosomes are small particles which are found individually in the cytoplasm and
also line the membranes of the rough ER. Ribosome produce protein. They could
be thought of as “factories” in the cell.
3.
Golgi
Body / Apparatus: Golgi bodies are stacks of flattened membranous stacks. It
temporarily stores protein which can them leave the cell via vesicles pinching
off from the Golgi.
4. Lysosomes: Lysosomes are small sac-like structure surrounded by a single membrane and containing strong digestive enzymes which when released can break down worn out organelles or food. The lysosome is also known as a suicide sac.
5.
Mitochondria:
The mitochondria are round “tube-like” organelles that are surrounded by a
double membrane with inner membrane being highly folded.
- The
mitochondria are often referred to as the “powerhouse” of the cell.
- These
mitochondria release food energy from food molecules to be used by the cell
- This process is called respiration.
- Some
cell (muscle cells) require more energy than other cells and so would have many
more mitochondria.
6. Vacuoles: They are fluid filled organelles enclosed by a membrane. They can store material such as food, water, sugar, minerals and waste products.