Cell Membrane: Structure and Function

• A Plasma Membrane is the gateway to the cell
• The Plasma Membrane is portrayed in a photograph of a cell membrane

Cell Membrane

• The cell membrane is flexible
• The cell membrane allows a unicellular organism to move

Homeostasis

• Homeostasis is a balanced internal condition of cells
• Homeostasis is also called equilibrium
• Homeostasis is maintained by the plasma membrane controlling what enters and leaves the cell

Functions of Plasma Membrane

• Plasma Membrane provides a protective barrier for the cell
• It plays an important role in regulating transport in and out of cell (selectively permeable)
• Proteins on the cell membrane allow cell recognition
• It provides anchoring sites for filaments of the cytoskeleton

Structure of the Cell Membrane

• The cell membrane consists of protein molecules, carbohydrate chains, protein channels, and lipids (bilayer)

Membrane Components

• The membrane consists of phospholipids, cholesterol, proteins, glycocalyx, and cytoskeleton and peripheral/ integral proteins

Phospholipids

• Phospholipids make up the cell membrane
• They contain 2 fatty acid chains that are nonpolar
• The head of a phospholipid is polar and contains a phosphate group

Fluid Mosaic Model

• The cell membrane is described as a "fluid mosaic model"
• Fluid because individual phospholipids and proteins can move around freely within the layer, like it's a liquid
• Mosaic because of the pattern produced by the scattered protein molecules when the membrane is viewed from above

Cell Membrane Properties

• Polar heads are hydrophilic, meaning "water loving"
• Nonpolar tails are hydrophobic, meaning "water fearing"
• These make the membrane "Selective"

Cell Membrane Composition

• The cell membrane consists of 2 layers of phospholipids called the lipid bilayer
  • Hydrophobic molecules pass easily
  • Hydrophilic do not pass easily

Solubility

• Materials that are soluble in lipids can pass through the cell membrane easily

Cholesterol

• Cholesterol is only present in animal cells
• Cholesterol stabilizes the membrane by reducing membrane fluidity and permeability to some smaller solutes

Semipermeable Membrane

• Small non-charged molecules move through easily
  • Examples: O2 and CO2
• Ions, and large molecules such as glucose and amino acids do not move through the membrane on their own, they must use transport proteins

Assignment

• This assignment requires a hand drawn diagram of the cell membrane
• Should be on physical paper, A4 or A3 in size
• Includes all of the parts, structures and terms
• Labels and annotations are required

Explore the cell membrane, the flexible gateway to the cell that maintains homeostasis by controlling what enters and leaves. Learn about its structure, including phospholipids, cholesterol, proteins, and its key functions such as protection, transport regulation, and cell recognition.