CLASS XBIOLOGY

NOTES CHAPTER - 1. CELL THE STRUCTURAL AND FUNCTIONAL UNIT OF LIFE

(REVISION)

1

CHAPTER-1

CELL THE STRUCTURAL AND FUNCTIONAL UNIT OF LIFE (REVISION)

Biology: The science which deal with the structure, organization, life processes, interactions, evolution and other aspects of living creatures is called Biology.

Bio + logy = Study + Life.

The term Biology was coined by “Lamarck and Treviranus” in 1802.

Father of Biology: “Aristotle.”

Living organisms: Living organisms are the compositions of complex molecules which perform certain life processes, collectively they are known as metabolic activities like Respiration, Reproduction, Breathing, execration etc.

2

Sequence of components in formation Of an organism.

Cell

Tissue

Organ

Organ System

Organism

3

Cell

Cell: Structural and functional unit of life. Because body of each and every living organism may be

unicellular or multicellular is made up of cell.

So, it is known as structural unit of life.

4

Tissue

Tissue is a group of cells that have a similar structure and act together to perform a specific function.

There are four different types of tissues in animals. Connective, muscle, nervous, and epithelial.

5

Organ

An organ is formed by a group of tissues in a living organism that have been adapted to perform a specific function. In higher animals, organs are grouped into organ system like lung, brain etc.

6

Organ System

Organ System is a group of organs that work together as biological system to perform one or more functions.

For example: Respiratory system, Digestive system and Reproductive System.

7

Cell Cytology: The Study of forms, structures and composition of cell is called cell cytology.

Father of cytology: Robert Hooke

Cell Biology: The branch of biology which deal with various aspects of structure, chemistry, development, genetics and functioning of cells is called Cell Biology.

The number increases to 100 trillion (100 X 1012) cell in the body of 60 kg human being.

25% (25 X 1012) of them are found in blood.

8

Cell: The unit of life

Cell was discovered by Robert Hooks.

He observed cork cells and coined the term cell which means enclosed compartments.

The cell discovered by Robert Hooks was dead.

The cork is dead tissue, these hexagonal compartments are surrounded by cell wall and nothing in them.

The cork slide of quarcus plant is used by Robert Hook for his experiment.

9

Living cell was first observed by Anton Von leeuwenhoek. Robert Brown discovered presence of nucleus in orchid

root. Robert Hook known as father of cytology. Anton Von leeuwenhoek is known as father of

bacteriology. Durjondin and Purkinje gave the term Protoplasm. Robert Hook published the entire information about his

experiment in his book Micrographia.

10

Cell theory M.schleiden in 1838 examined a number of plants and

observed that all

Plants are composed of cells of various types that form types that form the tissue.

T.Schwann in 1839 studied different types of animal cells and reported that cells had a thin boundary layer which is knows as the plasma membrane now,also concluded based on his studies on plant tissue that cell wall is unique to plant cells.

Schleiden and schwann proposed the cell theory,it did not explain how new cells are formed.

11

Cell theory states following postulates.

All living organisms are made up cells.

Cell is structural and functional unit of life.

Activities of an organism are sum total of activities and interactions of components.

Rudolf Virchew modifies the cell theory he states that:

Omnis Cellula- e-cellula. All cells arise from pre existing cell

12

Shapes of cell

Cells have various shapes.

For example red blood cells are circular and biconcave.

Nerve cells are long and irregular in shape.

WBCs are amoeboid in shape.

Goblet cells are columnar shapes.

Smooth muscles are spindle in shapes.

13

14

Sizes of cell

Smallest cell is PPLO (Pleuro Pneumonia like organism) 1.0 µm.

It is placed in between virus and bacteria.

Largest cell is of ostrich egg.

It is 7 ½ or 9 inches in size.

Longest cell is nerve cell. They vary in size from 4 microns to 100 microns (.004mm to .1mm).

15

Types of cell:

There are two types of cell:

a)Prokaryotic cell

b)Eukaryotic cell

16

Prokaryotic cell

Pro means Primitive and Karyon means Nucleus.

It means there is no membrane around the Nucleus.

The cell is without enclosed by any membrane bound genetic material is present in it.

For example: Bacteria.

They lack membrane bound cell organells.

17

Eukaryotic cell

Eu means True and Karyon means Nucleus.

True or advanced Nucleus is present in Eukaryotic cells.

Eukaryotic cell have membrane around the Nucleus.

They have membrane bound cell organells.

For example: Plants, Fungi etc.

18

Gross structure of cell Mainly cell is divided into three parts-

Cell membrane

Cytoplasm

Nucleus.

Note: Plant cell have an additional outer most non living layer called cell wall, which surrounds the cell membrane.

They (cell wall) is made up of a non living cellulose so, that we can say the cell wall is dead.

Cellulose is the most abundant macromolecule found on earth.

19

Protoplasm The living part (metabolic site) of a cell which is surrounded by

cell membrane is called protoplasm.

In protoplasm all the metabolic activities (reactions) are takes place.

Protoplasm is divided into to parts:

a) Cytoplasm

b) Nucleoplasm

Protoplasm = Cytoplasm + Nucleoplasm

Cytoplasm = Protoplasm - Nucleoplasm

Nucleoplasm = Protoplasm – Cytoplasm

20

Animal Cell21

Plant Cell22

Structure of nucleus23

24

Plastids

Plastids are found in plants cells.

They provide colour to fruits and flowers.

They helps in store of protein, starch and oil.

They trap solar energy to manufacture of food through the process of photosynthesis.

On the basis of presence of pigments the plastids are of two types:

a. The chloroplast having pigment

b. The leucoplasts which are colourless plastids.

25

Vacuoles

Plants cells have a large vacuole due to the amount of water the cell must hold to maintain its shape.

It creates turgor pressure.

Most plants store their waste materials in cellular vacuoles.

Centrioles

Centrioles are only found in animal cell.

Centrioles plays a role in the mitosis of animal cells, plants cells are able to reproduce without them.

26

27

28

29

Why lysosomes are knows as suicidal bags of the cells?

They contain hydrolytic enzymes. If the cell is damaged ,

the lysozymes undergoes autolysis and burst open.

This results in the release of those hydrolytic enzymes.

The released enzymes then digest their own cell and ultimately the cell dies, hence called as suicidal bags of cells.

30