Cell Membrane Structure and Functions

Cell Membrane Structure and Functions

• The cell membrane is a selective barrier, separating the cell's interior from the outside environment.
• It's composed of diverse lipids, carbohydrates, and proteins.
• Cholesterol is an important structural component, impacting membrane fluidity.
• LDL cholesterol can clog arterial walls.
• The membrane's structure impacts its function, with different proteins playing roles in transport, adhesion, recognition, and reception.
• Recognition proteins help the body recognize pathogens and trigger the immune response.

Membrane Structure

• The cell membrane is a phospholipid bilayer structure.
• Phospholipids have hydrophilic heads and hydrophobic tails.
• The bilayer arrangement is favored by the aqueous nature of the intracellular and extracellular environments.
• Molecules embedded in the membrane include proteins and glycolipids.
• Carbohydrate chains are only on the outside of the membrane or on peripheral proteins.
• The model describing the membrane's structure is the fluid mosaic model.

Membrane Fluidity

• Membrane fluidity is crucial for cellular processes like cell movement and protein incorporation.
• The presence of unsaturated hydrocarbon tails in fatty acids maintains membrane fluidity.
• Unsaturated hydrocarbon tails with kinks maintain fluidity at low temperatures.
• The presence of double bonds in fatty acids assists in maintaining membrane fluidity.
• Saturated bonds in fatty acids create a more viscous and rigid membrane at low temperatures.

Membrane Permeability

• The membrane is selectively permeable, meaning it regulates which substances enter and exit the cell.
• Size and chemical nature of molecules affect permeability.
• Polar molecules and larger molecules are often impermeable.
• Small, non-charged molecules are often permeable.
• Concentration gradients affect molecule movement.

Membrane Proteins

• Transport proteins (channel or carrier proteins) facilitate molecule movement across the membrane.
• Adhesion proteins hold cells together in animal tissues.
• Recognition proteins aid in cell recognition.
• Receptor proteins bind to specific molecules, enabling communication between cells.

Functions of the Plasma Membrane

• The cell membrane serves as a primary barrier for the cell.
• It enables cells to receive information or stimuli and allows the cell to move and grow.
• Other functions include selective transport, reception of stimuli, and barrier function.

Impact of Cholesterol on Plasma Membrane

• Cholesterol affects membrane fluidity and influences the structure's function.
• Removing cholesterol changes membrane characteristics and can adversely impact the cell.

Learning Objectives

• Students should be able to describe the structural components of the cell membrane.
• Students should be able to relate the structure and composition of the membrane to its function.
• Identifying different structural components of the plasma membrane.
• Describing the diverse roles of membrane proteins.
• Comparing membrane permeability for polar and non-polar molecules.

Type 2 Diabetes and Plasma Membrane Proteins

• Type 2 diabetes results from cells failing to recognize insulin.
• Receptor proteins in the plasma membrane are most affected.
• The specific receptor protein responsible for insulin recognition is impacted in type 2 diabetes, causing a disruption in proper blood sugar regulation.