Cell, in biology, the basic membrane-bound unit that contains the fundamental molecules of life and of which all living things are composed.
A single cell is often a complete organism in itself, such as a bacterium or yeast. Other cells acquire specialized functions as they mature.
These cells cooperate with other specialized cells and become the building blocks of large multicellular organisms, such as humans and other animals.
Although cells are much larger than atoms, they are still very small. The smallest known cells are a group of tiny bacteria.
Some of these single-celled organisms are spheres as small as 0.2 in diameter (1 = about 0.000039 inch), with a total mass of 10−14 gram—equal to that of 8,000,000,000 hydrogen atoms.
Cells of humans typically have a mass 400,000 times larger than the mass of a single bacterium, but even human cells are only about 20 across. It would require a sheet of about 10,000 human cells to cover the head of a pin, and each human organism is composed of more than 30,000,000,000,000 cells.
This article discusses the cell both as an individual unit and as a contributing part of a larger organism. As an individual unit, the cell is capable of metabolizing its own nutrients, synthesizing many types of molecules, providing its own energy, and replicating itself in order to produce succeeding generations.
It can be viewed as an enclosed vessel, within which innumerable chemical reactions take place simultaneously. These reactions are under very precise control so that they contribute to the life and procreation of the cell.
In a multicellular organism, cells become specialized to perform different functions through the process of differentiation. In order to do this, each cell keeps in constant communication with its neighbors.
As it receives nutrients from and expels wastes into its surroundings, it adheres to and cooperates with other cells. Cooperative assemblies of similar cells form tissues, and a cooperation between tissues in turn forms organs, which carry out the functions necessary to sustain the life of an organism.
The nature and function of cells
A cell is enclosed by a plasma membrane, which forms a selective barrier that allows nutrients to enter and waste products to leave. The interior of the cell is organized into many specialized compartments, or organelles, each surrounded by a separate membrane.
One major organelle, the nucleus, contains the genetic information necessary for cell growth and reproduction. Each cell contains only one nucleus, whereas other types of organelles are present in multiple copies in the cellular contents, or cytoplasm.
Organelles include mitochondria, which are responsible for the energy transactions necessary for cell survival; lysosomes, which digest unwanted materials within the cell; and the endoplasmic reticulum and the Golgi apparatus, which play important roles in the internal organization of the cell by synthesizing selected molecules and then processing, sorting, and directing them to their proper locations.
In addition, plant cells contain chloroplasts, which are responsible for photosynthesis, whereby the energy of sunlight is used to convert molecules of carbon dioxide (CO2) and water (H2O) into carbohydrates. Between all these organelles is the space in the cytoplasm called the cytosol.
The cytosol contains an organized framework of fibrous molecules that constitute the cytoskeleton, which gives a cell its shape, enables organelles to move within the cell, and provides a mechanism by which the cell itself can move. The cytosol also contains more than 10,000 different kinds of molecules that are involved in cellular biosynthesis, the process of making large biological molecules from small ones.
CELL FUNCTION.
- Cells do many work things to make sure our bodies function well and stay healthy. Cells need fuel to provide energy to do the work they do. They also need lots of water. Cells could not survive without oxygen. They get these substances from what we eat, drink, and the air we breathe The food is broken down into a sugar called glucose Water and Oxygen are absorbed into the cell and combine with the glucose to make energy. This energy production occurs in the mitochondria .
CELL ENERGY.
- The mitochondria are organelles that turn the glucose into energy. It is for this reason that they are called the "powerhouses" of the cell. The mitochondria absorb the fuel they need from the food we eat Before the mitochondria can absorb the food we eat, the food must be broken down. This is done by the lysosomes. Lysosomes contain enzymes . Enzymes are chemicals that break down the food we eat into a form the mitochondria can use. The mitochondria use enzymes to break down waste products, too. The waste goes into the cytoplasm. This waste is then eliminated from the cell.
CELL STRUCTURE.
- Cells are very small, yet very powerful. They are so small that you need a special tool to see them. This tool is called a microscope. Microscopes contain powerful magnifying lenses that help you see what cells look like by enlarging them There are about one trillion cells in the human body. One trillion looks like this: 1,000,000,000,000 These cells are classified into about 200 different types. Cells have different shapes, sizes, compositions and functions.
- Each cell is about 60% water. The remaining 40% is composed of structures, as well as chemicals, that a cell needs to function and sustain life. The cell membrane keeps the contents of a cell intact. The cell membrane also acts as a barrier between the inside of the cell and the environment outside the cell.
You must be logged in to post a comment.