Atom And Molecule

Atom

An atom is the smallest unit into which matter can be divided without the release of electrically charged particles.

It also is the smallest unit of matter that has the characteristic properties of a chemical element.

The atom is the basic building block of all matter.

Atoms are very small, they are smaller than anything that we can imagine or compare with.

More than millions of atoms when stacked would make a layer barely as thick as a sheet of paper.

Most of the atom is empty space.

The rest consists of a positively charged nucleus of protons and neutrons surrounded by a cloud of negatively charged electrons.

 

Atomic mass

Atomic mass is the average mass of atoms of an element, calculated using the relative abundance of isotopes in a naturally-occurring element.

Atomic mass indicates the size of an atom.

Although the mass is the sum of all the protons, neutrons and electrons in an atom.

Molecule

A molecule is in general a group of two or more atoms that are chemically bonded together, that is tightly held together by attractive forces.

A molecule can be defined as the smallest particle of an element or a compound that is capable of an independent existence and shows all the properties of that substance.

Atoms of the same element or of different elements can join together to form molecules.

 

Ion

Compounds composed of metals and non-metals contains charged species. The charged species are known as Ions.

An ion is a charged particle and can be negatively or positively charged.

Negatively charged ion is called an ‘anion’ and the positively charged ion, a ‘cation’.

A group of atoms carrying a charge is known as a polyatomic ion.

Types of Plant tissue and Animal tissue.

Types of Animal tissue:

Animal tissue are grouped into four basic types:

Epithelial tissue: The covering or protective tissues in the animal body are epithelial tissues.Epithelium covers most organs and cavities within the body.

It also forms a barrier to keep different body systems separate.The skin, the lining of the mouth, the lining of blood vessels, lung alveoli and kidney tubules are all made of epithelial tissue.

There are three principal shapes of epithelial cell:

(a) Squamous: Simple squamous epithelial cells are extremely thin and flat and form a delicate lining.

The oesophagus and the lining of the mouth are also covered with squamous epithelium.

(b) Columnar: A simple columnar epithelium is a columnar epithelium that is unilayered.In humans, a simple columnar epithelium lines most organs of the digestive tract including the stomach, small intestine, and large intestine. Simple columnar epithelial line in the uterus.

(c) Cuboidal: Cuboidal epithelium (with cube-shaped cells) forms the lining of kidney tubules and ducts of salivary glands, where it provides mechanical support.

Epithelial cells often acquire additional specialisation as gland cells, which can secrete substances at the epithelial surface.

Sometimes a portion of the epithelial tissue folds inward, and a multicellular gland is formed. This is glandular epithelium.

 

Muscular tissues: Muscular tissues consists of elongated cells, also called muscle fibers. This tissue is responsible for movement in our body.

Muscles contain special proteins called contractile proteins, which contract and relax to cause movement.

The body contains three types of muscle tissue:

(i) Skeletal muscle: Skeletal muscle is called “striated” because of its appearance consisting of light and dark bands visible using a light microscope. As shown in the diagram (on the right), a single skeletal muscle cell is long and approximately cylindrical in shape, with many nuclei located at the edges (periphery) of the cell.

(ii) Cardiac muscle: Cardiac muscle fibers are striated, branched (sometimes described as Y-shaped), and have a single central nucleus. These fibers are attached at their ends to adjoining fibers by thick plasma membranes called intercalated discs.

(iii) Smooth muscle: Unlike Skeletal and Cardiac muscle tissue, smooth muscle is not striated. Smooth muscle fibers are small and tapered – with the ends reducing in size, in contrast to the cylindrical shape of skeletal muscle. Each smooth muscle fiber has a single centrally located nucleus

 

Connective tissues:  Tissue that connects, supports, binds, or separates other tissues or organs, typically having relatively few cells embedded in an amorphous matrix, often with collagen or other fibres, and including cartilaginous, fatty, and elastic tissues.

Types of connective tissue:

(i) Areolar tissue: Areolar tissue is a common form of loose connective tissue.

Areolar tissue is found in many locations around the body.

One important area is the skin.The Areolar tissue located in the skin binds the outer layers of the skin to the muscle beneath.

Areolar tissue is also found in or around mucous membranes, and around blood vessels, nerves, and the organs of the body.

(ii) Adipose tissue: Adipose tissue, or fat, is an anatomical term for loose connective tissue composed of adipocytes.

Its main role is to store energy in the form of fat, although it also cushions and insulates the body.

Obesity in animals, including humans, is not dependent on the amount of body weight, but on the amount of body fat – specifically adipose tissue.

Adipose tissue is primarily located beneath the skin, but is also found around internal organs.

In the integumentary system, which includes the skin, it accumulates in the deepest level, the subcutaneous layer, providing insulation from heat and cold.

Around organs, it provides protective padding.

It also functions as a reserve of nutrients

(iii) Compact bone: Compact bone is made of concentric layers of osteocytes and bony matrix. Compact bones provide support to mammalian limbs.

Moreover, it is a storehouse of calcium and phosphorus.

(iv) Hyaline cartilage: A type of cartilage found on many joint surfaces; it contains no nerves or blood vessels, and its structure is relatively simple.

(v) Blood cell: Blood is a specialized body fluid. It has four main components: plasma, red blood cells, white blood cells, and platelets.

Blood has many different functions, including:

transporting oxygen and nutrients to the lungs and tissues.

carrying cells and antibodies that fight infection.

regulating body temperature.

forming blood clots to prevent excess blood loss.

bringing waste products to the kidneys and liver, which filter and clean the blood.

 

Muscular tissue: muscular tissue consists of elongated cells, also called muscle fibers. This tissue is responsible for movement in our body.

Muscles contains special proteins called contractile proteins, which contract and relax to cause movement.

Types of muscular tissue:

(i) Striated muscle: muscle tissue in which the contractile fibrils in the cells are aligned in parallel bundles, so that their different regions form stripes visible in a microscope.

Muscles of this type are attached to the skeleton by tendons and are under voluntary control. Also called skeletal muscle

(ii) Smooth muscle: muscle tissue in which the contractile fibrils are not highly ordered, occurring in the gut and other internal organs and not under voluntary control.

(iii) Cardiac muscle: The muscles of the heart show rhythmic contraction and relaxation throughout the life. These involuntary muscles are called cardiac muscles.

 

Nervous tissue: A cells posses the ability to respond to stimuli.

However, cells of the nervous tissue are highly specialised for being stimulated and then transmitting stimulus very rapidly from one place to another within the body.

The brain, spinal cord and nerves are all composed of the nervous tissue. The cells of this tissue are called nerve cells or Neurons.

Types of Plant tissues and Plant tissues

 Types of Plant tissues:

 

(1) Meristematic tissue: Meristematic tissues are group of cells, which have the ability to divide.

This tissue consists of small, cubodial densely packed cells, which keeps on dividing to form new cells.

These tissues are capable of stretching, enlarging and differentiate into other types of tissues as they mature.

Meristematic tissues give rise to permanent tissues.

 

There are three types of meristem based on the origin of meristematic cells :- Apical meristem, Lateral meristem and Intercalary meristem.

(a) Apical meristem is the region at the tip of the plant body. Thus, apical meristem helps in the increase in the height of the plant.

(b) Lateral meristem is a meristem located parallel to the sides of a stem or root, responsible for the thickening of the stem or root by the addition of secondary growth.

(c) Intercalary meristem is a meristem developing between regions of mature or permanent tissue (as at the base of the grass leaf).

 

(2) Permanent tissues:The tissues, which are derived from the Meristematic tissues, are called as permanent tissues.

They are the tissues, which have lost their ability to divide as they have attained their mature form.

Permanent tissues may be classified into three main groups:Simple,Complex and Special tissues.

(a) Simple Tissue:

Simple tissues are homogeneous and composed of structurally and functionally similar cells.

These are of three types:

(i) Parenchyma:

Parenchyma is the most common tissue which is morphologically and physiologically simple and unspecialized. These cells are found in epidermis, cortex, pericycle, pith etc. They are responsible for photosynthesis, storage of food, secretion etc.

(ii) Collenchyma:

Collenchyma are living tissues composed of more or less elongated cells and often have some chloroplast to carry on photosynthesis. It is generally situated below the epidermis.

(iii) Sclerenchyma:

Cells are long, thick-walled and lignified with tapering ends. These are fibre like in appearance and also known as sclerenchymatous fibre. These are dead cells and perform mechanical function.

(b) Complex tissue:

The complex tissues are composed of different types of cells performing diverse functions.

These  are of two types xylem and phloem:

(i) Xylem: Xylem is the one of the two types of transport tissue in vascular plants.The basic function of Xylem is transport water from roots to shoots and leaves,but it also transport some nutrients.

(ii) Phloem: It is the living tissue that transports the soluble organic compounds made during photosynthesis.

 

(c) Special tissue:

Special tissues are structurally modified and specially organized for secretary function.

These are of two types:

(i) Laticiferous tissue: These are specialized tube like structures known as laticiferous ducts found in many angiosperms.

These ducts are filled with white or yellow latex. Laticiferous ducts are of two types: Latex cells as found in madar and Latex vessels as found in rubber, papaya etc.

 

(ii) Glandular tissue: It consists of different types of glands which are formed by single cell or group of cells. These secrete resin, oil, mucilage, tannin, gums etc.

 

Tissue-Explanation and its Types

 Tissue

A group of cells that are similar in structure and work together to achieve a particular function is called tissue.

Or you can say a group of cells having common origin, similar structure and performing a definite function is called a tissue.

Organs are formed by the functional grouping together of multiple tissue.

All living organisms are made of cells.

In Unicellular organisms, a single cell performs all basic functions.

For example: Amoeba

In Amoeba, a single cell carries out movement,intake of food and respiratory gases, respiration and excretion.

But in Multi-cellular organisms there are millions of cells.Most of these are specialized to carry out a few functions. Each specialized function is taken up by a different group of cells.

Since these cells carry out only a particular function,they do it very efficiently. In human beings muscle cells contract and relax to cause movement,nerve cells carry messages, blood flows to transport oxygen,food,hormone and waste materials and so on.

In plants, vascular tissues conduct food and water from one part of the plant to other parts. So multi-cellular organisms show division of labor.

Cells specializing in one function are often group together in the body. This means that a particular function is carried out by a cluster of cells,called a tissue,is arranged and designed so as to give the highest possible efficiency of function.

Blood,phloem and muscles are all example of tissues.

Is there any difference between Plant and Animal tissue?

There are noticeable difference between plant tissues and animal tissues.

Plants are fixed they don’t move from one place to other which provides them structural strength.Most of these tissues are dead,since dead cells provide mechanical strength as easily as live ones and need less maintenance. The growth in plants are limited in certain regions.

On the other hand animals move around in search of food etc. They consume more energy as compare to plants.Most of there tissues are living. Cell growth in animals is more uniform.

Plant tissue

They are grouped into two basic types.

Meristematic tissues: Meristematic tissues are group of cells, which have the ability to divide.

This tissue consists of small, cubodial densely packed cells, which keeps on dividing to form new cells. These tissues are capable of stretching, enlarging and differentiate into other types of tissues as they mature. Meristematic tissues give rise to permanent tissues.

Permanent tissues:The tissues, which are derived from the Meristematic tissues, are called as permanent tissues.

They are the tissues, which have lost their ability to divide as they have attained their mature form.

Animal tissue

They are grouped into four basic types.

Epithelial tissue: Covers body surfaces and lines body cavities

Muscular tissues: Enables movement of structures within the body and movement of the entire person/animal

Connective tissues: Binds and Supports body parts

Nervous tissue: Enables responses to stimuli and coordinates bodily functions.

Cell

Cell

The Cell,(comes from Latin word cella,meaning “small room”) is the smallest unit of life. It is basic structural,functional, and biological unit of all living organisms.
Cell was discovered by Robert Hooke in 1665.
Cells are often called the “building blocks of life”.
All plants and animals are made of cells.
Organisms are classified as Unicellular (consisting of single cell,such as bacteria) and Multicellular (consisting of multiple cells,such as Plants and Animals).
Number of cells are varies from species to species.Human contains more than 10 trillion cells.
Most of cells are visible only under microscope.

Types of cells
There are two types of cells:
Prokaryotic cells: Single celled organisms.
Doesn’t contains Nucleus.
Eukaryotic cells: Single or multi cellular organisms.
Contains Nucleus.

Prokaryotic cells
The first form of life on Earth.
Prokaryotic cell is a unicellular organism lacking membrane bound organelles.
Most of prokaryotic cells are unicellular.They are generally small in size.
There Nucleur region is not well defined as they lack a Nucleus but it is known as Nucleoid.

Eukaryotic cells
Eukaryot are those organisms whose cells have a Nucleus and other organelles enclosed within membrane.
Eukaryotic organisms may be unicellular or multi-cellular and only Eukaryotes form multi-cellular organisms consists of many kinds of tissue made up of different types of cells.
They are generally larger in size.
Plants and animals cells are Eukaryotic cells.
Contains more than one chromosomes.

 

All cells posses DNA except for red blood cells.