Science and Biology

 SCIENCE

Science is an organized study of Knowledge which is based on experimentation. (OR)

 A branch of knowledge or study dealing with a body of facts or truths systematically arranged and showing the operation of general laws. (OR)

Science is a systematic enterprise that builds and organizes knowledge in the form of testable explanations and predictions about the universe.

 The word Science comes from the Latin word “Scientia” meaning Knowledge.

The term science was first coined by “William Whewell” in the year  1833.

Father of “Ancient Science” – Thales.

Father of “Modern Science” – Galileo Galilei.

 

What is Science ?

Science is an organized study of knowledge based on experimentation.

Science is process of thinking.

Science is a tool for searching the truths of nature.

Science is the way of exploring the world.

 

BIOLOGY

Biology is the branch of science which deals about living organisms. (OR)

Biology is the natural science that studies life and living organisms, including their physical structure, chemical processes, molecular interactions, physiological mechanisms, development and evolution.

 The word biology is derived from the Greek words  ( Bios  meaning life  and logos  meaning study )

The Term Biology was first coined by Lamarck and Treviranus in the year 1801.

Father of Biology – Aristotle

 

What is Biology ?

Biology  is defined as the science of life and living organisms.  An organism is a living entity consisting of one cell e.g. bacteria, or several cells e.g. animals, plants and fungi.

BIOLOGY HAS TWO MAIN BRANCHES:

1. Botany : Study of different aspects of Plants.

Theophrastus is known as Father of Botany.

2.Zoology : Study of different aspects of Animals.

Aristotle is known as Father of Zoology.

( Note :  Aristotle is called Father of  Biology as well as Zoology )

 

IMPORTANT TERMS OF BIOLOGY:

Anatomy,  Arthrology, Apiculture, Biotechnology, Bacteriology, Cytology, Cardiology, Dermatology, Ecology, Embryology, Ethology, Entomology, Food technology, Forensic science, Fermentation, Genetics, Histology, Haematology,  Hepatology, Immunology, Microbiology, Molecular Biology, Neurology, Osteology, Ornithology, Ophthalmology,  Paleontology, Physiology, Pathology, Radiology, Rhinology, Sonography, Veterinary science, Taxonomy, Horticulture, Viticulture, Agriculture, …………etc.

 

Mitochondria

 INTRODUCTION :

-  Mitochondria (“Power house of the cell”), were first discovered in 1857 by Physiologist Albert Von Kolliker, and later coined “ Bioblasts ” (life germs) by Richard Altman in 1886.

- The organelles were then again  renamed “Mitochondria” by Carl Benda  in 1897.

 STRUCTURE :

- Mitochondria are membrane-bound cell organelles that generate most of the chemical energy.

- The mitochondria ( derived from Greek word  in which  ‘Mitos’  means thread and ‘chodros’ mean granule ) are the centres for the cellular respiration and energy metabolism.

- Mitochondria are present in all Eukaryotic cells and are absent in Prokaryotes, also in bacterial cell.

- Mitochondria do not have a fixed shape. It can be  Cylindrical  or Rod or  Spherical or  Filamentous body or thread or spherical or club or sac etc like structures present in cytoplasm of cells.

- Mitochondria is surrounded by Double-layered Membrane. And they are Inner membrane  and Outer Membrane.

- The Inner membrane has many finger like fold structures called Cristae. And the fluid presents inside mitochondria is called  Matrix or mitosol which contains many enzymes and co-enzyme.

- On the inner membrane projecting into the matrix – a large number of particles called Elementary particles which have sphrerical head and a stalk.

- The outer membrane is smooth, Protective and it is more permeable to small molecules. And the outer membrane contains proteins known as Porins, which allow movement of ions into and out of the mitochondrion.

- Each Mitochondrion (singular) consists of a fluid filled space surrounded by double membrane envelope. The space present between the two membranes of the envelope is called Perimitochondrial space  or inter-membrane space.

 FUNCTION :  Mitochondria is the respiratory site of cellular respiration. Mitochondria synthesize energy rich compound ATP ( Adenosine Tri Phosphate ) Energy. Hence it is known as ‘Power House of the Cell’.

 

 { NOTE : Mitochondria is considered as “Prokaryotic cell inside Eukaryotic cell” OR “Cell within the Cell”.They possess their own DNA and Self-duplicating. Hence are also called Semi-autonomous organelles like chloroplast.}

Question :  Why mitochondria is known as ‘Power house of the cell’ ?

Answer :  Mitochondria is known as ‘Power house of the cell’,  because it generates Adenosine triphosphate  (ATP) energy by oxidizing the Carbohydrates and Fatty acids.

 

Mechanism of Photosynthesis ( Light and Dark reaction)

                                   

LIGHT   REACTION	DARK   REACTION
1.   Light  Dependent  Reaction	1. Light   Independent  Reaction
2.  Photo Chemical  Phase	2.Biosynthetic  Phase
3.  It requires Sunlight	3.It requires  or  does not requires Sun light
4.  Occurs  in  Grana  region	4.Occurs  in  Stroma region
5.   Photolysis  process takes place	5.Carbon fixation  process  takes place
6.   ATP  and  NADPH2   are formed	6.ATP and  NADPH2   are utilized
7.  Oxidative  Process	7. Reductive  Process
8.      Electrons  are  released	8.Electrons are utilized
9.    End Product are Oxygen,  water.	9.End  product  is   Glucose
10.  It involves Photolysis  or Hills reaction                                                                                                               H2O   →   H+    +   OH-           (water)  →  ( Hydrogen  ion) +  ( Hydroxyl   ion)	10.It involves Dark reaction  or carbon fixation                    H+   +   NADP   →   NADPH              NADPH+  +  CO2      →↓        Glucose                                          (ATP Energy)

Structure of Chloroplast

  CHLOROPLAST 

- Chloroplast were first reported or identified by Julius Von Sachs and the term chloroplast was coined by Schimper in 1883.

- The word Chloroplast is derived from the Greek word Chloros which mean “green” and Plastes which means “the one who forms”.

- Chloroplast (Cell organelle) is a Green coloured  plastid in the cells of green plants and green algae that contains Chloroplyll pigment and creates glucose/starch through photosynthesis.

- Chloroplast are found in all green parts of plants like leaves, young branches, stem, Calyx/sepals, unripe fruits etc

- Chloroplasts are spherical or oval or disc shape which are green in colour due to chlorophyll pigment.  

- Chloroplast is a membrane bound structure consisting of three membranes – Outer membrane,  Inner membrane and third internal membrane is Thylakoid membrane ( Grana).

(i) Outer Membrane :

 The outer membrane act as protective layer which is permeable to small organic molecules and ions which diffuses easily and outer membrane is not permeable to larger proteins.

(ii) Inner membrane:

Inner membrane consist of  Stroma and Grana

The intermediary fluid filled portion is called Stroma. It responsible for enzymatic reactions leading to synthesis of glucose, which in turn join together to form starch.

The inner membrane is less permeable and covers with proteins. Dark reaction occurs in Stroma  region.

(iii) Thylakoid Membrane :

The third layer forms stacked Sac (bag or pouch) like structures called as  Thylakoid or Grana  (plural). It helps to trap the solar energy which are connected by Stroma lamellae / Stroma thylakoid.  Light reaction occurs in Grana region.

-The space within a thylakoid is called Lumen.

- Substances found in chloroplast which capture sunlight are called Photosynthetic pigments. There are several types of photosynthetic pigments involved in the process to produce organic molecules like glucose in plants.

-Chlorophyll is a pigment which contain one atom of magnesium. Two major kinds of chlorophylls are associated with thylakoid membranes. Chlorophyll  ‘a’ is Blue-green in colour and chlorophyll ‘b’ is Yellow-green colour. 

-Around 250 to 400 pigment molecules are grouped as light harvesting complex or photosynthetic unit in each thylakoid. Such innumerable units function together in chloroplasts of green plants in the process of photosynthesis.

-During photosynthesis several events occur in the chloroplast some of them are :

(i) Conversion of light energy to chemical energy.

(ii) Splitting of water molecule ( Photolysis of water).

(iii) Reduction of Carbondioxide to Carbohydrates.

 

·         NOTE :{ In eukaryotic cell - Mitochondria and Chloroplast are  “Semi autonomous organelles” as it possess its own DNA. Semi autonomous organelles are organelles with DNA. The Presence of DNA in the chloroplast helps in self duplication. Hence chloroplasts are called “Semi-autonomous organelles.”}

    

      
                                                   Structure of Chloroplast

 MECHANISM OF PHOTOSYNTHESIS  ( LIGHT AND DARK REACTION)

                            

LIGHT   REACTION	DARK   REACTION
1.   Light  Dependent  Reaction	1. Light   Independent  Reaction
2.  Photo Chemical  Phase	2.Biosynthetic  Phase
3.  It requires Sunlight	3.It requires  or  does not requires Sun light
4.  Occurs  in  Grana  region	4.Occurs  in  Stroma region
5.   Photolysis  process takes place	5.Carbon fixation  process  takes place
6.   ATP  and  NADPH2   are formed	6.ATP and  NADPH2   are utilized
7.  Oxidative  Process	7. Reductive  Process
8.      Electrons  are  released	8.Electrons are utilized
9.    End Product are Oxygen,  water.	9.End  product  is   Glucose
10.  It involve Photolysis or Hills reaction                                                                                                    H2O   →   H+    +   OH-          (water)  →  ( Hydrogen  ion) +  ( Hydroxyl   ion)	10.It involves Dark reaction  or carbon fixation                     H+   +   NADP   →   NADPH              NADPH+  +  CO2      →↓        Glucose                                        (ATP Energy)

CELL

The fundamental organizational unit of life is the cell.

Cell is the basic unit of life.

A cell is the basic structural and functional unit of an organism.

All  organisms  are composed of cells and that all cells come from pre-existing cells.

Robert Hooke  observed the cell for the first time in 1665.

An organelle is an intracellular structure present in the cytoplasm of a cell

Cells are enclosed by a plasma membrane composed of lipids and proteins.

On the basis of the presence or absence of the organized nucleus, cells are categorized into two types that is Prokaryotic Cell ( Without organized Nucleus) and  Eukaryotic Cell ( With Organized Nucleus)

Prokaryotic  Cell - Cells that do not have a nuclear membrane bound nuclear material are called Prokaryotic cells OR  A cell without a distinct nuclear structure is called a Prokaryotic cell.  Example Bacteria,  Cyanobacteria, Blue green algae  etc.

Eukaryotic  Cell -  Cells  that have a nuclear membrane bound nuclear material are called Eukaryotic cells OR A cell with a distinct nucleus is called a Eukaryotic cell .  Example  Plant cell, Animal cell, Fungi etc.

PLANT    CELL	ANIMAL    CELL
Plant cells are usually large in size (Cubed or Rectangular in shape)	Animal cells are usually small in size ( Irregular in shape. Ex. Cells are round, oval, flattened or rod shaped, Spherical, concave, rectangular....)
Cell wall is present	Cell wall is absent
Plastids ( Ex. Chloroplast, Chromoplast) are present	Plastids are absent  ( Except Protozoan and Euglena)
Vacuoles are larger in size	Vacuoles are smaller in size ( Seen in Unicellular organisms)
Centrioles are absent	Centrioles are present
Plants cell can withstand the  greater changes in the external environment due to presence of  cell wall.	Animal cell cannot withstand  the greater changes in the external environment due to absence of cell wall.

 

PROKARYOTIC   CELL	EUKARYOTIC   CELL
Nuclear Membrane around  Nucleus is absent	Nuclear Membrane around nucleus is present
Membrane bound cell organelles are  absent. (Examples of membrane - bound  cell organelles are nucleus, endoplasmic reticulum, Golgi apparatus, mitochondria, plastids, lysosomes and vacuoles.)	Membrane bound cell organelles are Present
Nucleolus is absent	Nucleolus is present
Size of the Cell is generally small	Size of the cell is generally large
Most Prokaryotic cells are unicellular	Most Eukaryotic cells are Multicellular
It contains single chromosome  (A chromosome is an organized package of DNA found in the nucleus of the cell)	It contains more than one chromosome
Cell division occurs by Mitosis	Cell division  occurs by both Mitosis and Meiosis
Examples : Bacteria, Cyanobacteria, Blue green algae.	Examples : Plant cell, Animal Cell, Fungi….