DEFINITION OF A CELL.
The cell (from Latin cella, meaning “small room” is the basic structural, functional, and biological unit of all known living organisms. Cells are the smallest unit of life that can replicate independently, and are often called the “building blocks of life”. The study of cells is called cell biology.
Cells consist of cytoplasm enclosed within a membrane , which contains many biomolecules such as proteins and
nucleic acids. Organisms can be classified as unicellular (consisting of a single cell; including bacteria) or
multicellular (including plants and
animals). While the number of cells in plants and animals varies from species to species, humans contain more than 10 trillion (10 13 ) cells. Most plant and animal cells are visible only under the microscope, with dimensions between 1 and 100 micrometres .
CELL WAS DISCOVERED BY …
The cell was discovered by Robert Hooke in 1665, who named the biological unit for its resemblance to cells inhabited by
Christian monks in a monastery.
Cell AND ITS ENVIRONMENT
To survive in a dynamic world, cells evolved mechanisms for adjusting their organic chemistry in response to signals indicating environmental modification.
The changes will take several forms, as well as changes within the activities of pre-existing enzymne molecules, changes within the rates of synthesis of latest protein molecules, and changes in membrane-transport processes.
Chemicals that might pass into cells, either by diffusion through the cell membrane or by the action of transport protein and will bind on to protein within the cell and modulate their activities
TERMS ASSOCIATED WITH CELL AND ITS ENVIRONMENT.
Passive Transport: Movement across the cell membrane that doesn’t need energy from the cell.
Concentration Gradient: A distinction within the concentration of a substance across an area.
Equilibrium: A condition within which the concentration of a substance is equal throughout an area.
Diffusion: The movement of a substance from a region of high concentration to a region of lower concentration caused by the random motions of particles of the substance.
Osmosis: The diffusion of water through a by selective semi permeable membrane.
Hypertonic Solution: A solution that causes a cell to shrink due to osmosis.
Hypotonic Solution: A solution that causes a cell to swell due to osmosis.
Isotonic Solution: A solution that produces no modification in cell volume due to osmosis.
Ion Channel: A transport protein w/a polar pore that ions can pass through
Carrier Proteins: A transport protein which will bind to a selected substance on one side of a membrane, and free it on the opposite side.
HOW MATERIALS MOVE IN AND OUT OF A CELL
The Cell in its Environment-Physical and Biophysical Processes
Substances can move into and out of a cell through its semi-permeable cell membrane. There are three different processes through which materials can move in and out of a cell. They are:
• Through the process of diffusion,
• Through the process of osmosis and
• Through the process of active transport
The Penalty for Ignorance is Lack