Cell Theory

This was forwarded by Mathias schleiden and Theodor schwan.

• All living things are made up of cells.• The cell is the basic unit of structure and function.• The cell are the building block of structure in

living things.• The cell is derived from other cells by division.• The cell contains information for growth,

development and functioning.• The cell is the functioning unit of life :The

chemical reactions of life take place within cells.

The system International (SI) units of length

1 metre (m) = 1000 millimetres.

1mm(10-3m) = 1000 micrometres

1µm(10-6m) = 1000 nanometres

1nm(10-9m) = 1000 picometres

1 Angstrom = 10-10 m

PLASMA MEMBRANE

Plasma membrane

• It is the outer limiting membrane of both prokaryotic and eukaryotic cells.

• It is an ultra thin, elastic, living membrane.

• It can be seen observed only under electron microscope.

• It is chemically composed of protein, lipida and a little amount of oligosaccharides.

Plasmamembrane

• In 1960, Robertson proposed a unit membrane hypothesis.

• According to hypothesis, the outer and inner layers are proteins and about 2 nm thickness.

• Protein layers enclose the middle layer and composed of lipids.( mainly phospholipid )

• The middle layer is about 3.5 nm thickness.

Plasma membrane

• Singer and Nicholson have proposed a fluid mosaic model for the plasma membrane.

• In this structure protein molecules float and lipids are embedded.

Functions of Plasma membrane

• The cell membrane controls the passage of materials both into and out of the cell.

• It regulates the passage of water and dissolved substances.

• Water passes through the membrane by osmosis.

• Water soluble substances cross the membrane by diffusion or by active transport.

MITOCHONDRIA• The mitochondria are

filamentous or granular cytoplasmic organelles of all aerobic cells of higher animals and plants.

• They were first observed by KOLLIKER in 1850 as granular stractures in the striated muscles.

• They name mitochondria was given by BENDA. Certain cells contain large number of mitochondria e.g. ,Sea urchin contain 140,000-150,000 mitochondria.

• Oocytes of Amphibians –300,000 mitochondria.

• Liver cells of Rat –500 -1600 mitochondria.

• Algal cell – Only one mitochondria.

• The mitochondria may be filamentous or granular in shape.

• They vary in size from 0.5 µm to 2.0 µm.

• Each mitochondria is bound by two membrane.

• They are outer and inner mitochondrial membrane.

• The inner membrane is highly convoluted ,forming a series of infoldings known as CRISTAE.

• In between the two mitochondrial membrane there is a space called inter mitochondrial space.

• The inner part of the mitochondria is filled with matrix.

• The matrix contains lipids, proteins and circular DNA molecules.

• The matrix contain several enzymes.

• They play a role in oxidation, dehydrogenation, oxidative phosphorylation and respiratory chain of the cell.

• play a role in the oxidation of carbohydrates and fats.

• considered as the respiratory organs of the cells.

• synthesis the energy rich compound known as adenosine tri phosphate or ATP.

• So , mitochondria is refered as power houses of the cell.

• The cell cytoplasm contains a three dimensional network of sac–like and tubular cavities called cisternae .

• These structures are concentrated in the endoplasmic portion of the cytoplasm, the entire organisation is called the endoplasmic reticulum.

• This name was coined by Porter in 1953.• Generally ,it is found in the cell. But it is absent

in erythrocytes, egg cells and embryonic cells.

• There are two types of endoplasmic reticulum.

• They are Rough endoplasmic reticulum and smooth endoplasmic reticulum.

• Ribosomes are attached on the Rough endoplasmic reticulum.It is absent in smooth endoplasmic reticulum.

• RER is the site of systhesis of proteins.• SER is concerned with lipid metabolism.

• Morphologically ER may occur in three forms namely Lamellar form, Vesicular form and Tubular form.

• Lamellar form : These are long, flat , sac like tubules. Their diameter is about40-50 µm. mostly seen in cells of pancreas, notochord and brain.

• Vesicles : These are oval, vacuolar structure. diameter is about 25-500µm.

• Tubules : These are branched structures forming the reticular system along with the cisterne and vesicles.

• They have a diameter of 50 – 190µm

Functions :• It provides skeletal frame work to the cell.

• It facilitates exchange of molecules by the process of osmosis, diffusion and active transport.

• Enzymes of ER control several metabolic activities.

• They serve as intra cellular transporting system.

• It conducts intra cellular impulses.

• It helps to form nuclear membrane after cell division.

• SER synthesis lipids.

RIBOSOMERibosomes are small dense, rounded and granular particles.

They contain Ribo-nucleoprotein.• They occur either freely in the matrix of the mitochondria,

chloroplast and cytoplasm or remain attached with the membrane of the endoplasmic reticulum and nucleus.

The Ribosomes was described by G.E.PALADE in 1952.

The name Ribosomes was coined by R.B.ROBERTS in 1958.

RIBOSOME• Ribosomes were described by G.E.Palade in

1952. • The name was coined by R.B.Roberts in

1958.• The Ribosomes are spheroid structures with

a diameter of 150 to 250Å.• Each Ribosome is composed of two subunits.• One subunit is large in size and has a dome

like shape.• The other subunit is smaller in size and it

occurs above the larger sub units.• The Ribosomes are chemically composed of

RNA and Proteins.

RIBOSOME

• The Ribosomal RNA play a role in the protein synthesis.

• The Ribosomal proteins enhance the catalytic function of the r RNA.

• functioning of r RNA is under genetic control.

GOLGI COMPLEX

• The golgi complex was discovered by Italian neurologist, Camillo Golgi in 1873.

• The Golgi apparatus occurs in all animal cells except Red blood cells.It is absent in Bacteria.

Structure of Golgi apparatus.

• The Golgi bodies are made up cisternae (flattened sacs) arranged in parallel stacks, vesicles and vacuoles found around the ends of the cisternae.

• The membrane of golgi bodies is a lipoprotein membrane.

• Numerous cisternae are associated with each other and appear in a lamellar arrangement.

• In the lamellar arrangement the space between each cisternae is 20-30 nm.

A group of these cisternae is called the Dictyosome.A group of Dictyosomes constitute the Golgi- apparatus.

LYSOSOME• Lysosomes are tiny vesicles

surrounded by a single membrane.

• They are involved in intracellular digestion and destroying unwanted and aged organelles inside the cells.

• Lysosomes occur in all animal cells except mature mammalian erythrocytes.

• They are numerous in epithelial cells of secretory and excretory organs.

LYSOSOME• Lysosome is a round structure filled with a dense

material.Their size ranges from 0.2 to 5 μm.

• It contains 40 types of hydrolytic enzymes.

• The enzymes are mostly proteases, nucleases, glycosidases,lipases, phospho lipases , phosphatases and sulphatases.

• Lysosome were intially named as perinuclear dense bodies.

• The name lysosome was coined by C.deDuve in 1955.

KINDS OF LYSOSOMES

KINDS OF LYSOSOMES• Primary Lysosomes : Newly formed lysosomes before

participating in any cellular activity are called primary lysosomes. • They contain enzymes synthesized by the rough ER.

• Secondary Lysosomes :Lysosomes that are engaged in digestive activity in the cells are called Secondary lysosomes.

• The primary lysosomes fuse with food vacuole like pinosome or phagosome.

• Residual Bodies : Some materials are not digested in the secondary lysosomes. These substances may be released from the cell by exocytosis.

• Sometimes the debris may accumulate and the debris filled lysosomes are called Residual bodies.

• The residual bodies play an important role in the process of aging of cells.

• Autophagic vacuoles: Lysosomes also digest intracellular organelles and this process is known as autophagy.

• These vacuoles are formed during starvation or metamorphosis.

CENTRIOLES

• The centrioles are two cylindrical, microtubular structures found near the nucleus.

• When a centriole supports a flagellum or cilium,it is called the Basal body.

CENTRIOLES• The centrioles occur in most of the animal cells,

algal cells and some fern cells.• They are absent in prokaryotes, red algae,yeast

cells and flowering plants and some non- flagellated or non- ciliated protozoans.

• centrioles range in size from 0.15 – 0.25 µm in diameter.

• They are usually 0.3- 0.7 µm in length.

CENTRIOLES

Each centriole is formed of nine triplet microtubules.

Each microtubule has a diameter of 200•A in diameter.

microtubules are made up of a structural protein,tubulin, along with lipid molecules.

New centrioles are produced deNovo or are synthesized using an existing centriole as a template.

CENTRIOLES• The centrioles form the

basal body and the cilia.• In spermatozoan one

centriole gives rise to the tail fibre or flagellum.

• The centrioles are also involved in ciliary and flagellar activity.

NUCLEUSNucleus is the important

organelle of the cell and controls all metabolic processes and hereditary activities of the cell.

It was discovered by Robert Brown.

nuclear membrane was first revealed by O.Hertwig.

NUCLEUS

• All eukaryotic cell contains nucleus except mammalian erythrocytes.

• Many nuclei found in syncytial cell e.g., osteoblast

• The shape of the nucleus is spherical or elliptical.

• Each nucleus has a nuclear membrane, nucleoplasm, chromatin reticulum and nucleolus.

NUCLEOLUS

• The nucleus is surrounded by a nuclear envelope.• This envelope is comprised of two membranes of 5- 10

nm thickness.• The nuclear envelope is perforated by nuclear pores.• Each pore has a diameter between 10 nm to 100 nm.• The nucleus is filled with a transparent semisolid

matrix known as nucleoplasm or nuclear sap.

NUCLEOLUS

Nucleus contains one or more spherical collaidal structures called nucleoli.

Chemically , nucleolus contains DNA of nuclear origin, RNA, 70 types of ribosomal proteins, RNA binding proteins and nucleoproteins.

• The nucleus contains several thread like coiled structures.

• These are the chromatin fibres.• During cell division they become thick

ribbon like structures known as chromosomes.

• The chromatin is made up of De oxy-ribose nucleicacid and proteins.

CHROMOSOME

The chromatin fibres get

condensed into

chromosomes during cell

divisions.

capable of self-reproduction

and they play an important

role in heredity.

CHROMOSOMES

• The role of chromosomes in cell division was first explained by A. Schneider.

• Benden and Bovery reported that the number of chromosomes for each species is constant.

• Robert Feulgen showed that chromosomes contain DNA.

CHROMOSOMES

The number of chromosomes is constant for a particular species.

reproductive cells has one set of chromosomes and it is known as the haploid set.

• the haploid set is also known as the genome.• The body cells contain two haploid set or genomes

and are known as the diploid cells.

NUMBER OF CHROMOSOMES

PIGEON

FRUIT FLY

GORILLA

PARAMECIUM

HYDRA

HOUSE FLY

MAN

30-40

32

12 48

80

8

46