Wondering what is a cell exactly. A cell can be thought as a miniature (very tiny- not visible with our naked eyes) factory, which is capable of independent existence and can perform the important functions of life. It contains some specialized structures or organelles ( tiny little organs) with an aqueous environment bounded by cell membrane.
What is a cell
Definition:- cell is the basic structural and functional unit of all living organisms. An autonomous existing unit which can perform essential functions of all living organisms.
Organelles:- let me explain with one example, consider a human body as a (cell) and the organs present in human body as (organelles). As you know that various organs such as lungs, heart, kidney etc are integrated to work together to keep a human body in living state similarly different organelles such as ribosome, mitochondria, endoplasmic reticulum etc are integrated to do work to keep a cell in living state.
A huge diversity of organisms are harboring on this beautiful earth. These organisms from the tiniest bacteria to the most complex multicellular organisms, cell is the basic structural and functional unit of life which perform all essential functions to keep the organism in living state.
All these organisms are are basically classified into 2 categories:-
prokaryotes - contains all type of bacteria.
Eukaryotes - contains all organisms except bacteria( protista, fungi, plantae and animalia).
Later on we will discuss about the cell and organelles in details in other categories.
2)Robert Brown - discovered the nucleus of cell in orchid roots.
3)Anton Von Leeuwenhook - first to observe and describe a living cell. He observed bacteria, protozoa, spermatozoa, red blood cell etc.
Biological Evolution of cell-
The evolution of cells Is a fascinating story among many stories of evolution of life. Scientists belive that the first cells probably emerged around 3.5 billion years ago during the time known as Archean Era. In that Era the Earth was very different from today's earth. The earth was still forming at that time, the atmosphere( harsh environment)of earth was very different at that time.
Atmosphere was reducing( no oxygen was available) Mainly methane, ammonia, water vapours and carbon dioxide was present at that time. Despite of such harsh condition it is believed that first life was emerged during that archean Era.
These cells of archean Era, were created spontaneously from inorganic molecules in a reducing environment by the action of storm and sunlight. Sunlight broken water into hydrogen and oxygen and the lighter hydrogen escape in atmosphere. Oxygen combine with ammonia and methane to form water, carbon dioxide and others. Slowly slowly over the time, ozone was formed and as the temperature of the earth cools down, the water vapours condensed and fell as rain to fill the depressions on earth and forms oceans.
These organic molecules were then dissolved in the primitive ocean, concentrated and undergoes polymerization leads to formation of protobionts(also called coacervates- by J.B.S. Halden) and ( microspheres-by Sydney fox).
From these protobionts over the period assemble into more complex structures through a process of self organisation and catalysis. Eobionts are believed to exhibit some properties of metabolism and self replicating RNA molecules which leads to formation of prokaryotes slowly slowly over the period.
From these chemoheterotrops prokaryotes which were anaerobic must evolve into futher chemoautotrops which were also anaerobic which leads to evoluiton of anerobic photoautotrophs, condition is still anerobic at that time as the atmosphere was still reducing. Eventually over the period of time atmosphere becomes oxidative( presence of oxygen). Now from these anaerobic chemoautotrops there must be evolution of photoautotrophs which were aerobic(cyanobacteria) which ultimately would have lead to the evolution of eukaryotic cells.
Later we will study this biological Evolution of cell in evolution chapter.
Ans- cell is the basic structural and functional unit of all living organisms which is capable if independent existence and perform all essential functions of life.
Ques2-who defined cell?
Ans- Robert hook was the first to discovere a dead cell but ultimately Anton von leeuwenhook describe a living cell.
Ques3-what are the functions of cell?
Ans- cell perform various function for survival of an organism. Some of them are-
Ques4-what are prokaryotic cells?
Ans- prokaryotic cells are the single cell organisms which lack nucleus instead they have nucleoid and membrane bound organelles are absent. DNA present, nuclear membrane absent, histone proteins absent.
Ques5-what are organelles?
Ans- organelles are tiny entities or organs present in a cell which work together to keep a cell in living state.
Ques6-what are eukaryotic cells?
Ans- eukaryotic cells range from unicelluar to multicellular. They have nucleus as well as nuclear membrane and have membrane bound organelles and have histone proteins.
Some Discoveries:-
1)Robert Hook - discovered a cell In a thin slice of cork. He observe cell wall without cytoplasmic contents as the cell was dead.He published his discovery in his famous book-Micrographia.
2)Robert Brown - discovered the nucleus of cell in orchid roots.
3)Anton Von Leeuwenhook - first to observe and describe a living cell. He observed bacteria, protozoa, spermatozoa, red blood cell etc.
Biological Evolution of cell-
The evolution of cells Is a fascinating story among many stories of evolution of life. Scientists belive that the first cells probably emerged around 3.5 billion years ago during the time known as Archean Era. In that Era the Earth was very different from today's earth. The earth was still forming at that time, the atmosphere( harsh environment)of earth was very different at that time.
Atmosphere was reducing( no oxygen was available) Mainly methane, ammonia, water vapours and carbon dioxide was present at that time. Despite of such harsh condition it is believed that first life was emerged during that archean Era.
These cells of archean Era, were created spontaneously from inorganic molecules in a reducing environment by the action of storm and sunlight. Sunlight broken water into hydrogen and oxygen and the lighter hydrogen escape in atmosphere. Oxygen combine with ammonia and methane to form water, carbon dioxide and others. Slowly slowly over the time, ozone was formed and as the temperature of the earth cools down, the water vapours condensed and fell as rain to fill the depressions on earth and forms oceans.
These organic molecules were then dissolved in the primitive ocean, concentrated and undergoes polymerization leads to formation of protobionts(also called coacervates- by J.B.S. Halden) and ( microspheres-by Sydney fox).
From these protobionts over the period assemble into more complex structures through a process of self organisation and catalysis. Eobionts are believed to exhibit some properties of metabolism and self replicating RNA molecules which leads to formation of prokaryotes slowly slowly over the period.
From these chemoheterotrops prokaryotes which were anaerobic must evolve into futher chemoautotrops which were also anaerobic which leads to evoluiton of anerobic photoautotrophs, condition is still anerobic at that time as the atmosphere was still reducing. Eventually over the period of time atmosphere becomes oxidative( presence of oxygen). Now from these anaerobic chemoautotrops there must be evolution of photoautotrophs which were aerobic(cyanobacteria) which ultimately would have lead to the evolution of eukaryotic cells.
Conculsion-
- Cell is the basic structural and functional unit of all living organisms.
- From tiny single cell to multicellular complex organisms made up of cells.
- Organisms are broadly divided into 2 categories- prokaryotes and eukaryotes.
- Prokayotes contains all type of bacteria, while eukaryotes contains all organisms except bacteria.
- Robert hook discovered dead cell.
- Robert brown discovered nucleus of cell in orchid roots.
- Anton von leeuwenhook was first to observed various living cells.
- First cell would have arouse around 3.5 billion years ago during archean Era.
- During archean Era the environmental conditions were very harsh and atmosphere was reducing at that time.
- First organic cells formed from inorganic molecules were called protobionts.
- Protobionts eventually leads to evolution of eubionts, which leads to evolution of prokaryotes.
- Prokaryotes slowly and eventually leads to evolution of eukaryotic cells.
FAQ-
Ques1-what is a cell?Ans- cell is the basic structural and functional unit of all living organisms which is capable if independent existence and perform all essential functions of life.
Ques2-who defined cell?
Ans- Robert hook was the first to discovere a dead cell but ultimately Anton von leeuwenhook describe a living cell.
Ques3-what are the functions of cell?
Ans- cell perform various function for survival of an organism. Some of them are-
- Energy production
- Protein synthesis
- Cell replication and cell division
- Signal transduction
- Transportation
- Maintaining of shape of cell and homeostasis
- In defense mechanism
Ques4-what are prokaryotic cells?
Ans- prokaryotic cells are the single cell organisms which lack nucleus instead they have nucleoid and membrane bound organelles are absent. DNA present, nuclear membrane absent, histone proteins absent.
Ques5-what are organelles?
Ans- organelles are tiny entities or organs present in a cell which work together to keep a cell in living state.
Ques6-what are eukaryotic cells?
Ans- eukaryotic cells range from unicelluar to multicellular. They have nucleus as well as nuclear membrane and have membrane bound organelles and have histone proteins.
It is very helpful, nice explanation.
ReplyDeleteThanks, keep wat hing and keep studying
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