Cell structure and function

• The cell in a living organism is the basic structural and functional unit of life.
• Each cell is made up of several compartment called as cell organelles.
• A tissue is a group of similar cells performing a specific function.
• Many tissues together constitute an organ, organ forms organ system which further co-ordinates to form an organism.
• Each tissue, organ, organ system performs different functions in living system.
• This property of distribution of work among different organelles of the cell or among different tissues/ organs/ organ system etc is known as  division  of labour .

• Example: In the digestive system, different organs like mouth, stomach, large intestine perform different functions such as ingestion, digestion and absorption respectively.

Prokaryotic and eukaryotic organisms

• All multicellular organisms are made up of eukaryotic cells but unicellular organisms can be made up of either prokaryotic or eukaryotic cells.

Prokaryotes:

• The word prokaryote is comprised of two parts- pro: primitive; karyon: nucleus.
• The cells which contain primitive or undeveloped type of nucleus are known as prokaryotic cells and the organisms comprised of such cells are called as prokaryotic organisms.
• Such cells contain nuclear material which is not separated from cytoplasm due to absence of nuclear membrane.
• Single chromosome is present.
• Also membrane bound organelles are absent.
• Example: Bacteria

Eukaryotes:

• The word eukaryote is comprised of two parts - eu: true; karyon: nucleus.
• The cells which contain well-developed type of nucleus are known as eukaryotic cells and the organisms comprised of such cells are called as eukaryotic organisms.
• Such cells contain nuclear material which is separated from cytoplasm due to presence of nuclear membrane.
• Membrane bound organelles are present.
• They may contain either single or more number of chromosomes.
• Example: Eukaryotic - Unicellular- amoeba

Eukaryotic - Multicellular: plants - leaf

Basic components of the cell:

• All organisms are made up of cells. They all differ in terms of size, shape or number of the cells they are made up of. Despite of such differences, they all are made of basic components.

• Cell membrane is an outer boundary of the cell.
• Cytoplasm is a jelly like material present inside this boundary in which all other functional units (organelle) are embedded.
• Nucleus is control center of the cell.