Introduction to Cells

 

 

With the help of a microscope, an English scientist,Robert Hooke, first discovered the existence of cells in 1665.Scanning electron microscopes are used to examine the external parts of various organisms.Thetransmission electron microscope is used to view the internal structure of a cell and its organelles.Organisms that are made up of a single cell and perform all their vital activities, like reproduction, locomotion and digestion, are called unicellular organisms.Organisms that are made up of more than one cell are calledmulticellular organisms.Amoeba uses small finger-like projections called pseudopodia for locomotion and to capture prey.Paramecium is a single cell and is built in such a way that it performs all its vital activities, like reproduction, locomotion, digestion, and so on. TheWhite Blood Corpuscle (WBC) is the only animal cell that changes its shape.The branched structure of a neuron helps it to transfer messages to all parts of the body.

 

A microscope is an instrument used to see objects too small for the naked eye. An English scientist, Robert Hooke, discovered the existence of cells in 1665.Heis known for his book Micrographia, and for first using the word “cell” to describe the basic unit of life.

Scanning electron microscopes are used to examine the external parts of various organisms; It is a type of electron microscope that images a sample by scanning it with a high-energy beam of electrons in a raster scan pattern. The electrons interact with the atoms that make up the sample, producing signals that contain information about the sample’s surface topography, composition, and other properties such as electrical conductivity.

The transmission electron microscope (TEM) is used to view the internal structure of a cell and its organelles. TEM is a microscopy technique in which a beam of electrons is transmitted through an ultra-thin specimen, interacting with the specimen as it passes through it. An image is formed from the interaction of the electrons transmitted through the specimen; the image is magnified and focused onto an imaging device, such as a fluorescent screen, on a layer of photographic film, or to be detected by a sensor, such as a CCD camera.

Organisms that are made up of a single cell and perform all their vital activities, like reproduction, locomotion and digestion, are called unicellular organisms. Unicellular organisms can be found everywhere. The oldest forms of life, unicellular organisms existed 3.8 billion years ago, if not longer.

Organisms that are made up of more than one cell are called multi-cellular organisms. Most life that can be seen with the naked eye are multi-cellular, as are all animals and plants.

Amoeba uses small finger-like projections, called pseudopodia, for locomotion and to capture prey. Pseudopods or pseudopodia are temporary projections of eukaryotic cells. Cells with these structures are called ameboids.

Paramecium is a single cell, and is built in such a way that can perform all vital activities, like reproduction, locomotion, digestion, and so on.

The White Blood Corpuscle (WBC) is the only animal cell that changes its shape. WBC’s are responsible for protecting our bodies against invading bacteria and harmful micro-organisms. To find invading bacteria, they travel along with blood in blood vessels. Whenever they find invading bacteria, they squeeze through the blood vessels and intercellular spaces, catch the bacteria and kill it. To perform this task, WBC’s change their shape using pseudopodia similar to those in an amoeba.

The branched structure of a neuron helps it transfer messages to all parts of the body. A neuron, also known as a nerve cell, is an electrically excitable cell that processes and transmits information by electrical and chemical signalling.

 

 

 

 

Structure and Function of Cells

 

 

The black layer or the scab that you see on the wound is a result of the aggregation of dead Red Blood Cells (RBCs).The nose and the lungs form part of an organ system, the respiratory system.All organ systemswork together to form a complex organism. Thecytoplasm is a jelly-like fluid present between the nucleus and the cell membrane.The cell membraneallows the movement of minerals and other substances in and out of the cell.The nucleus controls the activities of a cell.Methylene blue is the stain placed on plant and animal cells to differentiate the nucleus under a microscope.Chromosomes are called vehicles of heredity because they carry genes and help in the inheritance or transfer of characteristics from the parents to the offspring.

Bacteria and blue-green algae that contain nucleoids are called prokaryotes.Organisms that have a well-organised nucleus are called eukaryotes.The nuclear material in unicellular organisms does not contain a nuclear membrane, and hence is called a nucleoid.The nucleolus is a small, spherical body in the nucleus.Chloroplast is a type of plastid involved in photosynthesis in plants.A vacuole is present in both plant and animal cells, but it looks much smaller in animal cells.