Lecture 6: The Cell Membrane Flashcards
Cell membranes?
A fluid mosaic of lipids and proteins. Phospholipids are amphipathic molecules. The fluid mosaic model-membrane is fluid with a mosaic of proteins embedded in it.
Amphipathic phospholipids?
Having both a hydrophobic and a hydrophilic end, able to interact with both polar and non-polar substances.
How are phospholipids amphipathic?
Phospholipids are amphipathic because one end is charged (hydrophilic) and the other is uncharged and non-polar (hydrophobic)
What are five functions of the cell membrane?
- Encloses and protects cell
- provides and supports mechanical structure
- transport in and out of the cell
- markers and signalling
- metabolic activities
Explain function of enclosing cell
Membrane forms a barrier between inside and outside of the cell, the different chemical environments can exist on each side of the cell membrane. These cell membranes are selectively permeable and allow certain molecules through and block the movement of others.
Explain function of providing mechanical structure: Cytoskeleton?
Proteins in the cell membrane attach to cytoskeletal fibres and help define and maintain shape of cell.
Explain function of providing mechanical structure: Extracellular matrix
In plant and animal tissues, the cell membrane interacts with the cell membrane of adjacent cells.
Explain function of providing mechanical structure: defines and encloses cell.
The membrane allows the cell to control the internal pressure and concentrations of intracellular components.
Transport in and out of the cell
Cell membranes allow transport of specific molecules across the cell membrane in either direction. Transport can be active or passive.
Passive transport?
Molecules drift and diffuse across membrane with the concentration gradient (from higher to lower concentration).
Bulk transport?
Endocytosis and exocytosis which move items in and out of the cell via secretory vesicles.
Active transport?
Molecules are pumped across the membrane against a concentration gradient (from lower concentration to a higher concentration).
Markers and signalling?
Surface protein markers embedded in the cell membrane identify the cell, enabling nearby cells to communicate. Cell membranes often include receptor proteins for interaction with specific chemicals (e.g. hormones, neurotransmitters, etc.)
Metabolic activities?
Enzymes that perform some metabolic activities are in the membrane.
