What is a cell?
All living things are made up of cells. Each of us has about 50 million million cells – an enormous number which is difficult to imagine. Each cell is a sort of bag made from a sort of skin called a membrane. The inside of a cell is watery and jelly-like. Cells are very small – you can’t see them just using your eyes. You need to use a microscope, which makes them look many times bigger that they actually are. If a cell is cut in half, it will not survive. So a cell can be considered as the smallest part of an organism that can survive on its own. Some organisms have only one cell, while more complicated organisms are made out of lots of cells. All cells have a membrane, which separates them from the outside world. The membrane protects the cell, and allows the cell to be selective about what is allowed in. The membrane is alive too, and can detect and respond to changes in the outside environment.
A cell is the basic structural and functional unit in all living things. The human body is composed of approximately 100 Trillion small microscopic compartments called cells. Groups of cells form tissues and groups of tissues form organs. Cells produce the raw materials, energy and waste removal necessary to live. Although cells vary enormously in size and function, they all have the same basic design.
By Jim V. Back To Main Page A cell is the very smallest unit of living matter. All living things including plants and animals are made up of cells. Cells are made of atoms, which are the smallest units of matter. There are many different kinds of cells. The two kinds you are most likely to be familiar with are animal and plant cells. Some of the differences between them are that plant cells have a cell wall and chloroplasts. Cells all have different sizes, shapes, and jobs to do. Did you know that the yoke from an ostrich’s egg is the biggest cell? Even the cells in a single organism may have different shapes, sizes, and jobs. Organisms like humans are made up of trillions of cells. There are also one celled organisms such as euglenas, amoebas, and bacteria. All cells have some parts in common. One part found in all cells is the cell membrane. The cell membrane surrounds the cell, holds the other parts of the cell in place, and protects the cell. Molecules can pass in and out of the ce
A cell is the smallest part of any living thing. There are many parts of a cell. Each part of a cell completes a certain function for the cell. All cells include the following parts: • Cell Membrane – forms the outer boundary of the cell and allows only certain materials to move into or out of the cell • Cytoplasm – a gel-like material inside the cell; it contains water and nutrients for the cell • Nucleus – directs the activity of a cell; it contains chromosomes with the DNA • Nuclear Membrane – separates the nucleus from the cytoplasm • Endoplasmic Reticulum – moves materials around in the cell • Ribosomes – make protein for the cell • Golgi Bodies – are used for packaging and secreting of energy • Mitochondria – break down food and release energy to the cell • Lysosomes – are chemicals used to digest waste • Vacuoles – are storage areas for the cell Some organelles are found only in Plant cells. These organelles are: • Cell Wall – provides structure to the plant cell • Chloroplasts
A cell is the most fundamental unit of biological life. All known life, except for viruses, is made up of cells. Cells are also the smallest metabolically functional unit of life, meaning the smallest unit that can take in nutrients from the bloodstream, convert them into energy, perform useful functions, and excrete waste. There are two primary types of cells in the kingdom of life – prokaryotic cells, smaller bacterial cells without a nucleus, and eukaryotic cells, larger plant and animal cells with a true nucleus. Cells are quite small. Prokaryotic cells are typically 1-10 µm (micrometers, or millions of a meter) across, while eukaryotic cells are 10-100 µm. Eggs are large single cells, and the largest known cell today is the egg of the ostrich, although prehistoric birds and some dinosaurs had eggs almost a foot in length. Every cell is produced from another cell, and each contains special genetic programming to manufacture proteins to replace things when they break down, divide, a
