STRUCTURAL COMPONENT

• Cell membrane - also known as plasma membrane, is a double layer of lipids and proteins that surrounds a cell and separates the cytoplasm (the contents of the cell) from its surrounding environment.
• Cell membrane is selectively permeable, which means that it only lets certain molecules enter and exit.
• Cell membrane can control the amount of some substances that go into or out of the cell.

  • All cells have cell membrane
• Cell membranes are composed primarily of phospholipids and proteins and are typically described as phospholipid bi-layers
• The cell membrane has a fluid consistency due to being made up of large part of phospholipids, and because of this, proteins move freely across its surface
• The multitude of different proteins and lipids in the cell membrane give it the look of a mosaic.
• Phospholipids - are the main component of cell membranes.

  • These are lipid molecules made up of a polar phosphate group head and two nonpolar fatty acid tails.
• POLAR PHOSPHATE GROUP HEAD

  • is hydrophilic which means "water-loving" (attracted)
• NONPOLAR FATTY ACID TAILS

  • are hydrophobic which means "water-hating" (repelled)
• The phospholipid bilayer also serve as binding sites for other substances such as proteins
• The properties of phospholipid molecules are: hydrophilic, hydrophobic, polar, and non-polar.

  • These allow molecules to spontaneously form a double-layered membrane
• When in water or an aqueous solution, which includes the inside of the body, the hydrophilic heads of phospholipids will orient themselves to be on the outside while the hydrophobic tail will be on the inside
• The technical term for the double layer of phospholipids that forms the cell membrane is phospholipid bilayer.
• Eukaryotic cells which make up the bodies of all organisms except for bacteria and archaea, also have a nucleus that is surrounded by a phospholipid bilayer membrane
• Cell membrane also contains glycolipids and sterols
• One important sterol is cholesterol, which regulates the fluidity of the cell membrane in animal cells.

  • When there is less cholesterol, membranes become more fluid, but also more permeable to molecules
• The amount of cholesterol in the membrane helps maintains its permeability so that the right amount of molecules can enter the cell at a time, not too many or too few.
• Cell membrane also contains many different proteins.
• Trans membrane proteins - proteins that are embedded in the membrane but stick out on both sides
• Receptor proteins - proteins that bind to signal molecules and send a signal to the cell
• ion channels - are proteins that allow ions into or out of the cell
• Cell membrane can also allow the cell to interact with its environment and communicate with other cells.

  • The cell can perform its roles due to its structural composition
• Cell/plasma/cytoplasmic membrane - biological membrane that separates the interior of a cell from its outside environment
• The primary function of the cell membrane is to protect the cell from its surroundings .
• Composed of a phospholipid bilayer with embedded proteins, the plasma membrane is selectively permeable to ions and organic molecules and regulates the movement of substances in and out of the cells.
• Plasma membrane must be very flexible in order to allow certain cells like red blood cells and white blood cells to change shape as they pass through narrow capillaries.
• Plasma membrane also plays a role in anchoring the cytoskeleton to provide shape to the cell and in attaching to the extracellular matrix and other cells to help group cells together to form tissues

  • It also maintain cells potential
• Cell membrane is a thin semi-permeable membrane that surrounds the cytoplasm of a cell
• CELL MEMBRANE'S FUNCTION

  Protect the integrity of the interior of the cell by allowing certain substances into the cell while keeping other substances out

  • It serves as a base of attachment for the cytoskeleton in some organisms and the cell wall in others
  • It helps support and maintain cell shape
• CELL MEMBRANE'S FUNCTION

  It regulates cell growth through the balance of endocytosis and exocytosis
• Endocytosis - lipids and proteins are removed from the cell membrane as substances are internalized
• Exocytosis - vesicles containing lipids and proteins fuse with the cell membrane increasing cell size
• Animal cells, plant cells, and fungal cells have plasma membrane

  • Internal organelles are also encased by membranes
• The cell membrane is primarily composed of a mix of proteins and lipids.

  • Depending on the membrane's location and role in the body, lipids can make up anywhere from 20-80% of the membrane, with the remainder being proteins
• Lipids - help give membranes their flexibility.

  Proteins - monitor and maintain the cell's chemical climate and assist in the transfer of molecules across the membrane.
• CELL MEMBRANE LIPIDS

  Phospholipids - are a major component of cell membrane

  • Lipid Bilayer - is semi-permeable, allowing only certain molecules to diffuse across the membrane.
• Phospholipids form a lipid bilayer in which

  • Their HYDROPHILIC (attracted to water) HEAD areas spontaneously arrange to face the aqueous cytosol and the extracellular fluid
  • While their HYDROPHOBIC (repelled by water) TAIL areas face away from the cytosol and extracellular fluid.
• CELL MEMBRANE LIPIDS

  Cholesterol - another lipid component of animal cell membrane, that helps keep cell membrane from becoming stiff by preventing phospholipids from being too closely packed together
• • Cholesterol molecules - selectively dispersed between membrane phospholipids
• Cholesterol is not found in the membranes of plant cells