Every cell is covered by a membrane that controls what can enter and leave the cell.
Learning Goal 1b
In all but quite primitive cells, a complex network of proteins provides organization and shape and, for animal cells, movement.
Learning Goal 2a
Within the cells are specialized parts for the transport of materials, energy capture and release, protein building, waste disposal, passing information, and even movement.
Learning Goal 2b
In addition to the basic cellular functions common to all cells, most cells in multicellular organisms perform some special functions that others do not.
Learning Goal 3
The work of the cell is carried out by the many different types of molecules it assembles, mostly proteins. Protein molecules are long, usually folded chains made from 20 different kinds of amino acid molecules. The function of each protein molecule depends on its specific sequence of amino acids and its shape. The shape of the chain is a consequence of attractions between its parts.
Learning Goal 4a
The genetic information encoded in DNA molecules provides instructions for assembling protein molecules.
Learning Goal 4b
The genetic information encoded in DNA molecules is virtually the same for all life forms.
Learning Goal 4c
Before a cell divides, the instructions are duplicated so that each of the two new cells gets all the necessary information for carrying on.
Learning Goal 5
Complex interactions among the different kinds of molecules in the cell cause distinct cycles of activities, such as growth and division. Cell behavior can also be affected by molecules from other parts of the organism or even other organisms.
Learning Goal 6
Gene mutation in a cell can result in uncontrolled division called cancer. Exposure of cells to certain chemicals and radiation increases mutations and thus the chance of cancer.
Learning Goal 7
Most cells function best within a narrow range of temperature and acidity. At very low temperatures, reaction rates are too slow. High temperatures and/or extremes of acidity can irreversibly change the structure of most protein molecules. Even small changes in acidity can alter the molecules and how they interact.
Learning Goal 8
A living cell is composed of a small number of chemical elements mainly carbon, hydrogen, nitrogen, oxygen, phosphorous, and sulfur. Carbon, because of its small size and four available bonding electrons, can join to other carbon atoms in chains and rings to form large and complex molecules.
Learning Goal 9
Some protein molecules assist in replicating genetic information, repairing cell structures, helping other molecules get in or out of the cell, and generally catalyzing and regulating molecular interactions.