THE FUNDAMENTAL UNIT OF LIFE: CELLS

PRESENTED BYRACHIT AHUJACLASS-9-C

Cell is the basic structural & fundamental unit of life. All cells whether they exist as called organisms or as part ,Perform similar basic functions such as respiration andnutrition, which are essential for their survival

• The cell is the smallest unit of life.

• All organisms are composed one or more cells.

• New cells arise from previously existing cells.

What is cell Made up of?A cell is a tiny mass of protoplasm which is surrounded by a membrane & is capaable of performing all functions of life . A typical cell is formed of three pairs:1.Plasma membrane or cell- membrane2.Nucleus3.Cytoplasm

1. Plasma membrane

This is the outermost covering of the cell that separates the contents of the cell from its external environment. The plasma membrane allows or permits the entry and exit of some materials in and out of the cell. The cell membrane , therefore is called a selectively permerable membrane.

Functions of the plasma membrane

1. It gives definite shape to cell 2. It seprates the contents of the cell from its

surrounding medium3. It provides mechanical barrier for the

protection of the internal contents of the cell4. It is selectively permerable5. It regulates the movement of ions in and out

of the cell

NUCLEUS

The NucleusThe Nucleus

The nucleus is a membrane bound structure that contains the cell's hereditary information and controls the cell's growth and reproduction. It is commonly the most prominent organelle in

the cellThe nucleus is surrounded by a structure called the nuclear

envelope. This membrane separates the contents of the nucleus from the cytoplasm. The cell's chromosomes are also housed within the nucleus. Chromosomes contain DNA which provides the genetic information necessary for the production

of other cell components and for the reproduction of life.

Functions of the nucleus

1. The nucleus controls all metabolic activities of the cell

2. It regulates the cell cycle3. It is concerened with the transmission of

heredity traits from the parent offsprings

CellsCellsTwo fundamental types:

1. Prokaryotic

2. Eukaryotic

Prokaryotic Cells

Prokaryotes

1. Prokaryotic cells are less complex 2. Unicellular 3. Do not have a nucleus 4. Most have a cell wall surrounding the

cell membrane 5.Include bacteria & blue- green

bacteria

Typical Animal Cell

Eukaryotic Cells

EUKARYOTES

1. More complex cells2. Includes both multicellular and

unicellularorganisms.3. Do have a true nucleus4. Organelles are internal structures in

cell’s that perform specific functions5. Eukaryotes include plant cells, animal

cells, fungi, algae, and protists.

The Cytoplasm

Cytoplasm

The protoplasmic mass of the inner cell to plasma membrane and excluding nucleus is called cytoplasm. When the cell is young , the cytoplasm completely fills the space between nucleus and plasma membrane. As it increases in size, a number of small cavities called vacuoles appear in the cytoplasm. It also contains many specialised cell organelles. Each of these organelles performs a specific function for the cell.

Cell organelles

Every cell has a membrane around it to keep its own contents separate from the external environment. Large and complex cells, including cells from multicellular organisms, need a lot of chemical activities to support their complicated structure and function. To keep these activities of different kinds separate from each other , these cells use membrane bound little structures (or organelles) within themselves.

Types of organelles

1.ENDOPLASMIC RETICULUM2. GOLGI APPARATUS3. LYSOSOMES4. MITOCHONDRIA5. PLASTIDS6. VACUOLES

The Endoplasmic Reticulum

Endoplasmic reticulum This is a complex network of tubes, the

lumen of which is filled with fluid. The two types of endoplasmic reticulum are seen .

They are;-

1. Rough endoplasmic reticulum2. Smooth endoplasmic reticulum

Functions of the (RER) & (SER)

RER looks rough under a microscope because it has particles called ribosomes attached to its surface. The ribosomes , which are present in all active cells , are the sites of protein manufacture.

SER helps in the manufacture of the fat molecules , or lipids, important for cell function. Some of these proteins & lipids helps in building the cell membrane.

The Golgi Apparatus

The Golgi Apparatus

Also known as golgi complex or golgi bodies , they consists of tiny elongates , flattened sacs (cisternae) , which are sacked parallel to one another along with some vacuoles and clusters of vesticles.

The function of the golgi body is to secrete certain hormones and enzymes . it also forms lysosomes . The golgi body is usually found close to the nucleus.

LYSOSOMES

These are membrane bound vesicular structures found in the cytoplasm . Each lysosome is surrounded by a single membrane and contains powerful digestive enzymes. These enzymes are made by RER .Lysosomes are involved in intracellular digestion of foreign food or microbes and are called DIGESTIVE BAGS. These are involved in autolysis or self- digestion of cells after their death, hence they are also called SUICIDAL BAGS. They are a kind of waste disposal system of a cell.

Ribosomes

Cells need to make proteins. Those proteins might be used as enzymes or as support for other cell functions. When you need to make proteins, you look for ribosomes. Ribosomes are the protein builders or the protein synthesizers of the cell. They are like construction guys who connect one amino acid at a time and build long chains.

Ribosomes are found in many places around the cell. You might find them floating in the cytoplasm (cytosol). Those floating ribosomes make proteins that will be used inside of the cell. Other ribosomes are found on the endoplasmic reticulum. Endoplasmic reticulum with attached ribosomes is called rough. It looks bumpy under a microscope. Those attached ribosomes make proteins that will be used inside the cell and proteins made for export out of the cell.

MitochondrionMitochondrion

Lysosome Function

ChloroplastsChloroplasts

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