BIOL 2130 Lecture Notes - Lecture 7: Semipermeable Membrane, Glycocalyx, Fluid Mosaic Model
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Chapter 3
Cells and Tissues
Cells
• Cells are the structural units of all living things
• The human body has 50 to 100 trillion cells
Chemical Components of cells
• Most cells are composed of four elements
1. Carbon
2. Hydrogen
3. Oxygen
4. Nitrogen
• Cells are about 60% water
Four Concepts of the Cell Theory
1. A cell is the basically structural and functional unit of living organisms
2. The activity of an organism depends on the collective activities of its cells
3. According to the principle of complementarity, the biochemical activities of cells are
dictated by the relative number of their specific subcellular structures.
4. Continuity of life has a cellular basis.
Anatomy of a Generalized Cell
• In general, a cell has three main regions or parts:
1. Nucleus
2. Cytoplasm
3. Plasma Membrane
The Nucleus
• Control center of the cell
o Contains genetic material known as deoxyribonucleic acid, or DNA
▪ DNA is needed for building proteins
▪ DNA is necessary for cell reproduction
• Three regions:
o Nuclear envelope (membrane)
▪ Consists of a double membrane that bounds the nucleus
▪ Contains nuclear pores that allow for exchange of material with rest of
the cell
▪ Encloses the jellylike fluid called the nucleoplasm
• Nucleoli
o Nucleus contains one or more nucleoli
o Sites of ribosome assembly
o Ribosomes migrate into the cytoplasm through nuclear pores to serve as the site
of protein synthesis
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