• Robert Hooke an optic seller, observed a piece of cork through his hand made lens and found many identical small chambers.
• In Latin word, ‘cellula’ means “a small chamber”.
• So Robert Hooke named this chamber as cell in 1665.
• He became a famous scientist by showing the cell magic through his lens. Robert Hooke initiated the work to invent a microscope.
• Following him, Robert Brown, a school teacher continued and invented an advanced microscope.
• He discovered the nucleus

Types of Cell

1. Prokaryotic cell
2. Eukaryotic cell

• Cells of plants and animals are not similar
• Bacteria and some algae are made up of single cell
• Their cells lack membrane bound organelles
• Cells that do not contain membrane bound organelles and possess “incipient nucleus “ are called prokaryotic cells, i.e., simple cells Eg.:Bacteria
• Cells that contain a well-defined nucleus, nuclear membrane and all the cell organelles are called eukaryotic cell.i.e.,complete cells Eg.Cells of plants and animals

CELL ORGANELLE

1. Cell membrane and cell wall
2. Cell Membrane (Plasma membrane or Plasmalemma )

The contents of the cell are enclosed  by a thin, delicate living membrane called cell membrane `

Functions

• Plasma membrane selective regulates the entry and exit of the substances into and out of the cell.
• It is called a selectively permeable membrane or semi-permeable membrane.

Cell Wall

• Cell wall is present only in plant cells. Most of the plant cell walls aremade of cellulose.
• The cell wall consists of three layers namely, middle lamella, primary wall and secondary wall.

Functions of cell wall

1. It provides mechanical strength to the cell
2. It protects the protoplasm against injury.

Protoplasm

The colorless material

• Comprises of two components namely cytoplasm and nucleus of the cell
• E.Purkinjee coined the term protoplasm
• ‘Proto’means ‘first’ and ’plasma’means colloid

Cytoplasm

             It protects the nucleus and help in various cell activities controlled by nucleus.

Functions of Cytoplasm

• Cytoplasm helps in intracellular distribution of enzymes, nutrients andother biomolecules within the cell.
• Synthesis of different types of biomolecules such as proteins, nucleotides,fatty acids etc., takes place in the cytoplasm.

Endoplasmic Reticulum

• Endoplasmic reticulum is a complicated interconnected system of membrane bound channels and tubules.It is spread throughout thecytoplasm. .
• There are two types of Endoplasmic Reticulum

1. Rough Endoplasmic Reticulum(RER)
2. smooth Endoplasmic Reticulum(SER)

Rough Endoplasmic reticulum (Granular endoplasmic reticulum)

                        This type of endoplasmic reticulum possesses rough walls because the ribosomes remain attached.

Smooth endoplasmic reticulum (Agranular endoplasmic reticulum)

                       The walls are smooth and ribsomes are not attached to its membrane.

Functions

1. Provides large surface area of the metabolic activities of the cell.

                       2.Rough endoplasmic reticulum plays an important role in protein synthesis.

3. Smooth endoplasmic reticulum is involved in the synthesis of steroid,hormones and lipids.

Golgi Complex or Golgi apparatus

• The Golgi apparatus was first described by Camillo Golgi.
• Golgi complex consist of saucer-like compartments called cisternae,network of interconnecting tubules.
• At the peripheral regions, in plant cells ,Golgi apparatus is referred to as dictyosomes.

Functions

1. Formation of lysosomes
2. Synthesis of cell wall and cell membrane

Lysosomes

• Small membrane bound vesicles which contain various types of digestiveenzymes.
• These serve a intracellular digestive system, hence they are calleddigestive bags. `
• Lysosomes are involved in the destruction of aged and wornout cellular organelles.
• Therefore also called demolition squads or scavangers or cellularhousekeepers (or) uicidal bag of the cell.

Functions

• Lysosomes are involved in the intracellular digestion of food particlesingested by the cell through endocytosis.
• The lysosomes of WBCS (white)

Thus take part in natural defense of the body.

Ribosomes

• Ribosomes are small granular structures made up of ribo nucleic acid(RNA) and proteins.
• Each ribosome consists of two subunits – a small subunit and a large subunit

RNA and form a structure called polyribosome.

There are two types of ribosomes

1. 70S – Ribosome – 30S and 505 subunits. It is seen in Prokaryotic cells.
2. 80S – Ribosome – Itis made up of 40’s and 60s subunits. It is seen in eukaryotic cells. ‘

Functions

• Ribosomes play an important role in protein synthesis. So they are called, protein factories of the cell

Vacuoles

• Vacuoles are fluid – filled sacs bound by a single membrane and arepresent in plant cells as well as in certain protozoans as food vacuoles and contractile vacuoles.
• In plant cells, major portion of the cell is ocoupied by vacuoles and arebound by the definite membrane called tonoplast

Functions

• Vacuolesstore and concentratemineral salts as well as nutrients.
• They maintain proper osmotic pressure in

Mitochondria

• Mitochondria are globular or cylindrical organelles.
• Each mitochondrion is bound by two membranes – an outer continuousmembrane and an inner membrane thrown into folds called cristae.
• The inner chamber is filled with homogenous dense material called the matrix.
• The cristae have pin headed bodies called F1 particles or Oxysomeswhichplay an important role in respiration.
• The matrix of mitochondria contains enzymes necessary for the oxidation of food during respiration and release of energy in the form of ATP molecules.
• The mitochondria are called power houses of the cell
• The mitochondria contain proteins

Functions

• Mitocondria synthesize energy rich compounds auch as ATP
• Mitochondria provide important intermediates for the synthesis of several biochemicals like chlorophyll, Cytochromes, steroids, aminoacids etc.

Plant cell:  Plastids:

• Chloroplasts: These are green coloured plastids which possess the photosynthetic pigment chlorophyll.
• Each chloroplast consistsofa double membrane envelope and a matrix.
• The inner membrane is arranged along the length of the plastids as lamellae.
• At certain regions, the lamellae are thickened and appear like pile of coins.
• These are called the grana.
• Each granum consists of disc shaped membranous sacs called thylakoids.
• Inside these grana, the chlorophyll is located. The non-thylakoid portion of the matrix is called stroma.
• It contains a number of enzymes involved in photosynthesis

Centrosome

• Centrosome is present in animal cells and in certain lower plants. It isabsent in prokaryotic cells and in higher plant cells.
• It contains a pair of small, hollow granules called centrioles

Functions

• Centrioles play an important role in the fomation of spindle fibres during cell division.

Nucleus

• Nucleus is the major central structure the cell. It is a dense spherical structure embedded in the cytoplasm
• Nucleus has a double membrane envelop called nuclear envelope.
• Nuclear envelope encloses a ground substance called nucleoplasm or karyolymph.
• The nucleoplasm has two types of -nuclear structures i. the nucleolus and
• Chromatin.
• The nucleolus is a spherical body rich in protein and RNA. It is the site of ribosome formation. There may be one or more nucleoli in the nucleoplasm.
• The chromatin is a network of fine threads composed of genetic materialDNA (Deoxyribo nucleic acid) and proteins. During cell division chromatin is condensed into thick cord like structures called Chromosomes.
• The chromosomes contain genes and each gene is responsible for one hereditary character of the organism.
• Genes contain information for inheritance of features from parents to nextgeneration in the form’ of DNA molecule.

Functions

1. Nucleus controls all the metabolic activities of the cell
2. It controls the inheritance of character from off-springs
3. It controls Cell division

Organization-Cells-Tissues-Organs-Organ System

• In multicellular animals ,cells multiply by process of cell division and specialize themselves to perform a particular function

Tissues

• A group of cells having common origin, structure and function is referred to as tissue

Animal Tissues

• On the basis of the function we can think of different type of animal tissues
• These may be classified into five broad categories

Epithelial Tissues

• Epithelial tissues cover most organs and cavites with in biody.Since the cells are closely packed ,there is very little  space between them and the absence of intercellular space is the characteristic of epithelial tissues

A Squamous Epithelium

• Sauamous epithelium consists of single layer of flattened cells with central disc like nucleus
• The inner lining of the cheek and the membrane s within the body are examples for this epithelium

Function

• Protection is their function. In the alveoli they help in exchanges of gases

1. Columnar Epithelium

• The cells are cylindrical and tall, the height of each cell being greater than its width.
• The oval nuclei are usually found at the base of these cells. Example the inner-lining of the intestine.

Function

• Secretion of enzymes in the stomach and absorption of digested food in the intestine

1. Cuboidal Epithelium

The  cells of this  epithelium are cube shaped. The walls of the ducts and the glands are examples.

Function

• The tissue helps in secretion and reabsorbtion of water in kidney tubules

1. Ciliated Epithelium

• In structure,it is like columnar ephithelium. In addition they contain at their five margins a number of fine protoplasmic projections called cilia

Function

• Remove the dust particles by the vibration of the cilia.

1. Sensory Epithelium

• Some of the epithelial cells are modified to respond to stimuli and they form sense organs.

Vascular Tissues

• This is a liquid tissue adapted for the transportation of the nutritive materials, respiratory gases, excretory materials and others.
• It consists of 55% plasma and 45% blood cells.
• They are:

1. Red Blood Cells (Erythrocytes): RBC
2. White Blood Cells (Leucocytes): WBC

• Blood Platelels (Thrombocytes)

Erythrocytes:

• The Red Blood Cells present in vast majority. Each red cellis a circular or biconcave disc without a nucleus.
• These are formed in the bone marrow. Life’s between 100 to 120 days
• It contains haemoglobin a respiratory pigment that chiefly carries oxygen from the lungs to the other parts of the body
• Leueocytes: The nucleated ewhite blood cells are irregular and contain no pigment.
• They are produced in the bone marrow and in the lymph glands. Life span of WBC is two or three week

Thrombocytes:  

• The bloodplatelets are the smallest of the blood cells and responsible forthe clotting of the blood when blood vessels are damaged.

Connective tissues

• The cells of connective tissues are loosely spaced and embedded in aninter cellular matrix.

They are:

1. Adipose tissue
2. Supportive tissue

Adipose Tissue:

• This is modified for storing fat. The inter cellularmaterial is more or less absent.
• It is found chiefly below the skin and in between the internal organs.
• Supportive Tissue: This tissue gives support to the entire body .The supportive tissues are of three types
• They are

1. Cartilage Tissue
2. Bone Tissue
3. Areolar Tissue

Cartilage Tissue:

• It has widely spaced cells. The solid matrix is compased of proteins and sugars
• Cartilage Smoothens bone surface at joints and is also present in the nose, ear, trachea and larynx

Bone Tissue:

• It forms the framework that supports the body.Bone cells are composed of calcium and phosphorus compounds
• Two bones can connected to each other by the ligament

Areolar Tissue:

• It is found between the skin and the muscles around the blood vessels, nerves and in the bone marrow. It fills the space inside the organs

Nervous Tissue

• The nervous tissue is formed of nerve cells called neurons and nerve fibres
• Neurons: It is a structural unit of the nervous system. It has a cell body called cyton which assumes different shapes in the different regions of the nervous system, and a long tail called axon.
• The protoplasm of the cyton has a number of small dark granules referred to a nissel bodies.

Muscular Tissues

• It consists of elongated cells also called muscle fibres.
• Muscular tissue contains proteins called Contractile Proteins.

Striated Muscle:

• Since these muscles are attached to the Skeleton, theyare also called Skeletal Muscles.
• It has number of nuclei placed also near the Periphery. They are covered by a membrane called sarcolemma.
• Since their contraction, is under conscious they are also called voluntary muscles.

Non-striated muscles

• The cells are arranged to form a sheet of muscular tissue commonly found in the wall of the digestive tract, urinary bladder and other internal organs

 Cardiac muscle:

• In structure, they are in between the Striped and unstriped muscle fibers. These are found only in the heart
• Dark and Light portions are present in the muscle of the heart show rhythmic contraction and relaxation throughout life.

Organs

• Two or more kinds of tissues are associated together to form organ.
• For example, the eye has epithelial tissue, connective tissue, nervoustissue and muscular tissue. `

The eyes (Photoreceptor)

• The sense organ eye in concerned with vision. The eye which is sphericalin shape is kept in the orbit of the skull.

1. Sclerotic coat

• The outer sclerotic coat is white in colour except in the front where it forms the transparent cornea

2. The middle choroids coat

• It is highly vascularised and deeply pigmented. In front of the eye the choroid coat forms he iris and lens

3. The inner coat (Retina)

• Retina is the sensitive part of an eye. It contains two types of receptor cell the rods and cones
• Rods are sensitive to different shades of light but not colour.Cones are sensitive to colour
• The lens is transparent, elastic and biconvex in shape.It is attached by ligaments to the ring shaped cillary muscles
• The Aqueous humors is a clear, watery liquid between the cornea and the lens
• Vitreous humour helps in image formation and also maintain the spherical shape of the eye

Diffusion or Exchange of Substances Between Cells and their Environment

• Materials are exchanged between the cytoplasm and external environmentacross the plasma membrane may be passive or active.

Passive Transport

• It is a type of diffusion in which an ion or molecule crossing a membranemoves its electrochemical or concentration gradient
• No metabolic energy is consumed.
• Passive transport occurs by three processes namely

1. Osmosis
2. Simple diffusion
3. 3.Facilitated diffusion

Osmosis

• The process by which the water molecules pass through a membrane from a region of higher water concentration to the region of lower water concentration is known as Osmosis.
• The process in which the water molecules enter into the cell is known asendosmosis.
• The process in which the water molecules move out of the cell is known asexosmosis.
• In plant cells due to excessive exosmosis, the cytoplasm along with theplasma membrane shrinks away from the cell wall. This process is known as plasmolysis.

Simple diffusion

• In simple diffusion, molecules of gases such as oxygen and carbon dioxide enter the cell through the plasma membrane without the help of any permease

Facilitated diffusion

• This is a special type of passive transport. Ions or molecules cross the membrane rapidly
• Specific permeses in the membrane facilitates their crossing. Like simple diffusion,it also does not require any metabolic energy.It occurs only in the direction of a concentration gradient

Active transport

• It is always against the concentration gradient. (i.e. from lower concentration to higher concentration
• In this process the solute paticles move against their chemicalconcentration or electrochemical gradient.
• Energy is required for thisprocess

Bulk transport

         Cells continuously import or export large molecules across the plasma membrane. Macromolecules are secreted out from the cell by exocytosisand are injested into the cell from outside by endocytosis

Exocytosis

        Be means of carrier molecules. It is quite common in secretory or excretorycells.

Endocytosis   

        Infolding or extension of the plasma membrane to form a vesicle orvacuole. Itis of two types.

1. Phagocytosis
2. Pinocytosis

Phagocytosis (cell eating)

       Substances are taken up in solid form. Cells which involve in this processare called. e.g. white blood cells,

Pinocytosis (Cell drinking)

       Substances are taken up in fluid form. E.g Amoeboid protozoans andcertain kidney cells) Pinocytosis occur in plants also