chapter - 1

Cell: the fundamental unit of life

Important terms

1.​ Cytology: the study of cell concerned with the structure and function of cell is

called cytology

2.​ Cell theory: cell theory presented by two biologist schleiden and scwann in the

year 1839 this theory states that all living organism are made up of cells and

cell is the basic unit of life

3.​ microscope : a piece of equipment that makes very small objects look big enough

for you to be able to see them there are two types of microscope simple light

microscope and compound microscope

4.​ Unicellular: they consist of single cell

yeast,protozoa,amoeba,paramecium,chalamydomonas and bacteria are some

unicellular organism

5.​ Multicellular: they are formed by the combination and collection of cells having

specialised functions which are well coordinated for ex: Humans.

6.​ Plasma membrane: it is the outer covering of the cell it is the living thin

delicate,elastic which allows the entry and exit of some substance it

also present the movement of some substance hence it is called

selectively permeable membrane

7.​ Diffusion: it is the spontaneous movement of substance from a region of

higher concentration to the region of lower concentration until equal

concentration is achieved

8.​ Osmosis: osmosis is defined as the movement of (water) from its

higher concentration to its lower concentration through a

semipermeable membrane
9.​ Endocytosis: endocytosis is a cellular mechanism which adds

substance into the cell the material to be internalised is surrounded by a

cell membrane area

10.​Exocytosis: exocytosis is an essential plant and animal cell cycle

because it perform the opposite role of endocytosis in exocytosis

cellular and molecular vesicles are transported to the cell membrane

and is a process of moving materials from the cell to the exterior of the

cell

11.​Plasmolysis: the shrinkage of protoplasm from the cell wall due to

exosmosis is called plasmolysis

12.​Deplasmolysis: if a plasmolysed cell is immediately kept in hypotonic

solution

the cell regains the original shape which is called deplasmolysis

13.​Prokaryotic cell: prokaryotic cell containing organism are called

prokaryotes these types of organism have primitive types of cell the cell

lacks nuclear memberane around the genetic material DNA thus the

undefined nuclear reigon in the cytoplasm is known as nucleoid

14.​Eukaryotic cell: eukaryotuic cell containing organism are called

eukaryotes theese types of organism have complete and advanced

types of cell each cell has cell memberane and nnuclear membrane with

cytoplasm

Tables

1.​ Difference between diffusion and osmosis

 Diffusion Osmosis

It is the movement of Movement of substance from

substance from the region of the region of higher

higher concentration to lower concentration to lower

concentration concentration through a

semipermiable membrane

It is applicate for all types of It is applicable for liquids

mediums i.e solid,liquid and molecules only

gaseous molecules

There is no requirement of This process requires

selectively permeable selectively permeable

memberane membrane

It depends on the kinetic It depends on the presence of

energy of the molecules of solute (salts) molecules in the

diffusing substance only system

2.​ Comparison between cell wall and cell membrane

Cell wall Cell memberane

It is non-living boundary wall It is living boundary wall

It is found in plant of cell only It is found in both plants and

animal cell

It is a permeable boundary wall It is selectively permeable

membrane

It is found outside the cell It is found outside the

memberane cytoplasm

3.​ Difference between prokaryotic cell and eukaryotic cell

Prokaryotic cell Eukaryotic cell

The size of the cell is very The size of the cell is generally

small varying from 1µ𝑚 to 10 between 5µ𝑚 to 100µ𝑚

µ𝑚

well - defined nucleus is Well-defined nucleus is

 absent present

In place of nucleus thre is Nucleoid is absent

nucleoid

It has only one chromosomes It has more than one

chromosomes

There is no nucleus Thre is nucleolus present

inside the nucleus

Nuclear memberane is absent Nucllear membereane is

present

Membarane bound cell is Membrane bound cell

organelles are absent organells are present

The cell division is by fission The cell division is by miotic

or by budding there is no division

mitosis

Function of cells

1.​ Nucleus: nucleus is a large centrally located spherical cellular component it

has a double layered covering called nuclear memberane these two layers from

an envelop and is connected to a system of membrane called endoplasmic

 reticulum the nuclear envelope has fluid known as nucleoplasm which allows

the transfer of materials between nucleoplasm and cytoplasm

2.​ Cytoplasm: In cell biology, the cytoplasm describes all material within a

eukaryotic cell, enclosed by the cell membrane, except for the cell nucleus. The

material inside the nucleus and contained within the nuclear membrane is termed

the nucleoplasm. The main components of the cytoplasm are cytosol (a gel-like

substance), the organelles (the cell's internal sub-structures), and various

cytoplasmic inclusions. The cytoplasm is about 80% water and is usually

colorless.

3.​ Cell organelles: The cellular components are called cell organelles.

These cell organelles include both membrane and non-membrane bound

organelles, present within the cells and are distinct in their structures

and functions. They coordinate and function efficiently for the normal

functioning of the cell. A few of them function by providing shape and

support, whereas some are involved in the locomotion and reproduction

of a cell.
4.​ Mitochondria: mitochondria is also known as powerhouse of the cell

each mitochondria rod shaped double membrane structure the outer

membrane is very porous but smooth and the inner membrane is folded

into large finger like structure called cristae

function

●​ Mitochondria release the energy required for various life-releated

chemical activities in the form of ATP (adinosine triphosphate)

molecules

●​ ATP is also called the cell power currency the body uses energy that is

stored in ATP for production of new chemical compound and chemical

work
5.​ Plastids: they found in plant cell only they are the largest cytoplasmic

organelles pf plant easily visible under light microscope plastids are pf

three types

❖​ Lecoplast (colourless plastids)

❖​ Chloroplast (green plastids)

❖​ Chromoplastids (coloured plastids,other than green)

Function

●​ Leucoplast are mainly organelles that store materials like

starch,oils, and proteins granules

 ●​ Chloroplasts manufacturer food through photosynthesis it is also

known as “the kitchen of cell” it gives the green colour to leaves

and stems

●​ Chromoplasts impart colour (other than green) to the

flowers,fruits

6.​ Endoplasmic reticulum: the endoplasmic reticulum (ER) is a large

network of tubes and sheets attached to the membrane there are two

types of endoplasmic reticulum they are smooth endoplasmic reticulum

(SER) and rough endoplasmic reticulum (RER)

Functions
●​ It is the site for protein and fat synthesis. RER is involved in

protein synthesis while SER involves for lipids synthesis

●​ It provides mechanical aid to cytoplasm and acts as a pathway for

material distribution

●​ It proteins and lipids are synthesised in endoplasmic reticulum

during cell division some of these proteins and lipids help in

building new membranes this process is also known as

membrane biogenesis

●​ Some of proteins and lipids synthesised in ER function as

enzymes and hormones

●​ A function of ER is therefore to serve as channels for the

transport of materials between different region of cell

Golgi apparatus: the golgi apparatus was first described by

camillio golgi it is made up of a system of membrane-bound

vesicles arranged in stacks called cisterns

Functions

●​ The synthesised product near the ER is packed and

delivered to different targetes inside or outside the cell

through golgi apparatus

●​ Product,storage,alteration and packaging in vesciles are

some function of golgi apparatus in some cases,complex

sugar in the golgi apparatus can be made from simple

sugars
 ●​ The golgi apparatus participles in the formation of

lysosomes

Lysosomes: lysosmes are small spherical bodies with a single walled

membrane lysosomes are sacs filled with digestive enzymes that are

membrane bound RER makes these enzymes

Function
 ●​ Lysosomes are are a type of cell waste management system by

digesting any foreign material

●​ When there is a disturbance in cell metabolism the lysosomes burst the

cell get damaged and the enzymes present in the lysosomes digest their

own cell

●​ Lysosomes help in keeping the cell dry foreign particles such as

bacteria or meat as well as old organelles end up lysosomes splitting

them into small pieces

●​ Lysosomes digest and stored food during prolonged hunger to provide

energy for cellular metabolism

Ribosomes: they are tiny membraneless granules found attached to the

surface of endoplasmic reticulum and free in cytoplasm they are rich in

proteins and RNA each ribososmes has two subunits: small and large

Function
●​ They are thesites of protein synthesis that’s why ribosomes are protein

factories of the cell