cell structure

• Seeley’s ESSENTIALS OF Anatomy & Physiology Tenth Edition includes Cinnamon Vanputte, Jennifer Regan, and Andrew Russo.
• Cell Structures and Their Functions is a chapter in Seeley’s ESSENTIALS OF Anatomy & Physiology Tenth Edition.
• Organelles are specialized structures in cells that perform specific functions, such as the nucleus, mitochondria, and ribosomes.
• Cytoplasm is a jelly-like substance that holds organelles.
• Some tumors are benign and some are malignant (cancer).
• There are various causes for cellular aging, including the existence of a cellular clock, the presence of death genes, DNA damage, the formation of free radicals, and mitochondrial damage.
• In some adult tissues, apoptosis eliminates excess cells to maintain a constant number of cells within the tissue.
• Malignant tumors can spread by a process, termed metastasis.
• Tumors are abnormal proliferations of cells due to problems occurring in the cell cycle.
• The cell membrane, or plasma membrane, is the outermost component of a cell and forms a boundary between material inside the cell and the outside.
• The fluid-mosaic model is the model used to describe the cell membrane structure, which contains phospholipids, cholesterol, proteins, and carbohydrates.
• A phospholipid molecule has a polar head region that is hydrophilic and a nonpolar tail region that is hydrophobic.
• The cell membrane has selective permeability, which allows only certain substances to pass in and out of the cell.
• Some substances, like O2 and CO2, can pass directly through the cell membrane’s phospholipid bilayer.
• Some substances must pass through transmembrane protein channels, such as Na+ through its channels.
• Some substances require carrier molecules to transport them across the cell membrane, such as glucose.
• Some substances require a vesicular transport across the membrane, which involves a vesicle fusing with the cell membrane for transport.
• Passive membrane transport does not require the cell to expend energy.
• Active membrane transport does require the cell to expend energy, usually in the form of ATP.
• Passive membrane transport mechanisms include diffusion, osmosis, and facilitated diffusion.
• In cotransport, the diffusing substance moves in the same direction as the initial active transported substance.
• Facilitated diffusion does not require ATP for energy.
• A major example of active transport is the action of the sodium-potassium pump present in cell membranes.
• Receptor-mediated endocytosis occurs when a specific substance binds to the receptor molecule and is transported into the cell.
• Pinocytosis has much smaller vesicles formed, and they contain liquid rather than solid particles.
• The vesicles move to the cell membrane and fuse, ultimately releasing the material by exocytosis.
• Carrier-mediated transport mechanisms include facilitated diffusion and Active transport.
• Active transport processes accumulate necessary substances on one side of the cell membrane at concentrations many times greater than those on the other side.
• Some water-soluble, electrically charged or large sized particles cannot enter or leave through the cell membrane by diffusion.
• Endocytosis is a process that that brings materials into cell using vesicles.
• Secondary active transport uses the energy provided by a concentration gradient established by the active transport of one substance, such as Na+ to transport other substances.
• The sodium-potassium pump moves Na+ out of cells and K+ into cells.
• These substances include amino acids, glucose, and some polar molecules produced by the cell.
• Facilitated diffusion is a carrier-mediated transport process that moves substances across the cell membrane from an area of higher concentration to an area of lower concentration of that substance.
• Examples of exocytosis are the secretion of digestive enzymes.
• In countertransport, the diffusing substance moves in a direction opposite to that of the initial active transported substance.
• Carrier molecules are proteins within the cell membrane involved in carrier-mediated transport.
• Exocytosis involves the use of membrane-bound sacs called secretory vesicles that accumulate materials for release from the cell.
• Phagocytosis is often used for endocytosis when solid particles are ingested.
• Active transport is a carrier-mediated process, requiring ATP, that moves substances across the cell membrane from regions of lower concentration to those of higher concentration against a concentration gradient.