bbio302

• Cells are the structural units of all living things.
• The human body has 50 to 100 trillion cells.
• A cell has three main regions or parts:

  1.        Nucleus

  2.        Cytoplasm

  3.        Plasma membrane
• The Plasma Membrane is the transparent barrier for cell contents. It contains cell contents and separates cell contents from surrounding environment.
• Phospholipids are polar: The charged end interacts with water, the fatty acid chains do not. It is this property of polarity that makes phospholipids a good foundation for cell membranes.
• The activity of an organism depends on the collective activities of its cells.
• A cell is the basic structural and functional unit of living organisms.
• According to the principle of complementarity, the biochemical activities of cells are dictated by their structure (anatomy) which determines their function (physiology).
• Continuity of life has a cellular basis.
• Most cells are composed of four elements: Carbon- 11%, Hydrogen- 59%, Oxygen- 24%, Nitrogen- 3-4%.
• Cells are about 60-80% water.
• The nucleus is the control center of the cell and contains genetic material known as deoxyribonucleic acid, or DNA.
• DNA is necessary for building proteins and for cell reproduction.
• The nucleus consists of three regions: the nuclear envelope, the nucleolus, and chromatin.
• The nuclear envelope is a membrane that bounds the nucleus and contains nuclear pores that allow for exchange of material with the rest of the cell.
• The nucleolus is a dark-staining region in the nucleus that is the site of ribosome assembly.
• Ribosomes migrate into the cytoplasm through nuclear pores to serve as the site of protein synthesis.
• Chromatin is composed of DNA wound around histones (proteins) and is scattered throughout the nucleus and present when the cell is not dividing.
• Chromatin condenses to form dense, rodlike bodies called chromosomes when the cell divides.
• Amino Acids are building blocks of protein
• Glycoproteins are branched sugars attached to proteins that abut the extracellular space.
• Glycocalyx is the fuzzy, sticky, sugar-rich area on the cell’s surface
• The nuclear envelope (membrane) encloses the jellylike fluid called the nucleoplasm.
• Tight junctions are impermeable junctions that bind cells together into leakproof sheets.
• In tight junctions, plasma membranes fuse like a zipper to prevent substances from passing through the extracellular space between cells.
• Desmosomes are anchoring junctions, like rivets, that prevent cells from being pulled apart as a result of mechanical stress.
• Desmosomes are created by buttonlike thickenings of adjacent plasma membranes.
• Gap junctions, also known as communicating junctions, allow communication between cells.
• Molecules can travel directly from one cell to the next through gap junctions.
• Hydrophilic (“water loving”) polar “heads” of phospholipids in the plasma membrane are oriented on the inner and outer surfaces of the membrane, while hydrophobic (“water fearing”) nonpolar “tails” form the center (interior) of the membrane.
• The interior of the plasma membrane, formed by the hydrophobic tails, makes the membrane relatively impermeable to most water-soluble molecules.
• Proteins are responsible for specialized membrane functions such as enzymes, receptors for hormones or other chemical messengers, transport as channels or carriers, and amino acids, which are the building blocks of protein.
• The three regions of the nucleus are: nuclear envelope, nucleolus, and chromatin.