CELLS
BRIDGE COURSE
Some Basic Concepts Of Biology
CELLS
🔴Cells are the fundamental structural unit of living organisms and basic units of life.
🔴 Why is cell called structural and functional unit of life?
All the living organisms are made up of one or more cells ,hence cell is called the structural unit of life.
All the functions of life of an organisms are performed by the cell.Cells also become specialised to perform specific functions,hence it is called the functional unit of life.
🔴 Cell was a chance discovery by Robert Hooke in the year 1665.
🔴 Robert Hooke while conducting an experiment observed very small boxes in a thin slice of cork (bark of a tree). He named these boxes 'cellulae'meaning little rooms.Later on it was shortened and called as cells.
🔴 Cell biology is the study of cells in all aspects of their structure and functions.
🔴 Cells are too small to be seen by naked eye so an instrument called microscope is used to study cells.
🔴 Microscopes are high resolution instruments that are used for observing fine details of very small objects.
The two common types of microscopes are:
1. Light or compound microscope: invented by Knoll and Ruska in 1932. But it was used first time in the year 1940.
2. Electron microscope: invented by Hans Jansen,Zacharias Janson and Hans Lippershey.
Unicellular organisms and multicellular organisms
🔴 The organisms which are made up of single cells are called unicellular organisms.
Examples: amoeba,paramoecium, bacteria and chlamydomonas.
They have shorter lifespan.
🔴 The organisms which are made up of a number of cells are many cells are called multicellular organisms.
Examples: fungi (except yeast )plants and animals.
They have longer lifespan.
NOTE
🔴 Smallest cell - PPLO (mycoplasma)
🔴 Largest cell - Ostrich egg
🔴 Longest animal cell - Nerve cell
Prokaryotic cell and eukaryotic cell
🔴 The cell that lacks a true nucleus and membrane bound organelles are called prokaryotic cell.
🔴 The organisms having prokaryotic cell are called prokaryotes (pro- primitive ,karyote - nucleus).
🔴 Examples :bacteria and cyanobacteria (blue green algae).
🔴 The cell having a true nucleus and membrane bound organelles are called eukaryotic cell.
🔴 The organisms having eukaryotic cell are called eukaryotes (eu - true, karyote - nucleus).
Examples : plants animals and protozoans
🔴 Protozoans are group of single celled organisms.Examples :rhizopoda, flagellate and amoeba.
Differences between a plant cell and an animal cell
🔴 Cell wall is present in plant cell and absent in animal cell.
🔴 Plastids are present in plant cell and absent in animal cell.
🔴 Centrosome is absent in plant cell and present in animal cell.
🔴 Vacuoles is single,large and at the centre in plant cell and vacuoles are many and small in animal cell.
🔴 Nucleus lies on one side in the peripheral cytoplasm in plant cell and it lies in the centre of the animal cell.
🔴 The size of the plant cell are larger compared to the size of animal cells which are smaller.
NOTE
🔴 Smallest organelle is ribosome.
🔴 Largest cell organelle in plant is plastid.
🔴 Largest cell organelle in animals is mitochondria.
🔴 Largest cell structure is nucleus.
🔴 Suicide bag of the cell is lysosomes.
🔴 Powerhouses of a cell is mitochondria.
🔴 Kitchen of the cell is chloroplast.
🔴 Protein synthesis occurs in ribosome.
🔴 Selectively permeable membrane is plasma membrane.
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TEST TO EVALUATE YOURSELF
One Marks Questions:
1.What is cell?
2.Who discovered cell?
3.Name the largest egg.
4.When did Robert hooke discover cell?
5. Who invented electron microscope?
6. Who invented compound microscope?
7. What are prokaryotic cell? Give two examples.
8. What are eukaryotic cell? Give two examples.
9. What do you mean by unicellular organisms?
10. What are multicellular organisms?
11. Give two examples each for unicellular organisms and multicellular organisms.
12. Why is cell called structural unit?
13. Why is a cell called a functional unit?
14. Name the instrument used to study cells.
15. What is cell biology?
QUIZ
Name the followings:
1. Largest animal cell.
2. Smallest cell.
3. Largest cell.
4. A group of single celled organisms.
5. Smallest organelle of a cell.
6. Powerhouse of a cell.
7. Kitchen of the cell.
8. Largest cell organelle in animals.
9. Protein synthesis of a cell.
10. Largest cell organelle in plant cell.
11. Suicide bag of a cell.
12. Selectively permeable membrane of a cell.
13. Largest cell structure.
14. The organelle which is single and large in plant cell.
15. Organi absent in plant cell.
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