Unit 1.1 - Cell Membrane

Cell

a single basic living, structural, and functional unit enclosed by a membrane

comes in various shapes that are based on their function

Plasma Membrane

a highly selective permeable membrane enclosing all the internal contents of a living cell

holds the interior structural scaffolding (cytoskeleton) in place to maintain cell shape

the more metabolically active a membrane is, the more protein it contains

Selective Permeability

a property of cell membranes that means each substance has its own permeability through a specific type of membrane

allows the creation of an intercellular condition to be different from surroundings

Cytoplasm

consists of all the cellular contents inside the cell between the plasma membrane and the nucleus

composed of cytosol and organelles

Cytosol

fluid portion of cytoplasm

with water, dissolved solute (e.g. electrolytes) and suspended particles such as proteins and nucleic acids

Organelles

structures enclosed with discrete intercellular membrane in various shapes, sizes, and functions

Plasma Membrane Structure

"fluid mosaic model" - plasma membrane is a mosaic of lipids with various proteins dissolved within it

basic structural framework of the plasma membrane is the lipid bilayer

plasma membrane are mostly phospholipids that are amphipathic (have polar & non-polar parts)

polar region (head) containing phosphate is hydrophilic, non-polar region (tail) containing fatty acid is hydrophobic

"like seeks like" head regions face watery fluid, tail regions face each other

Plasma Membrane Function

structural support - through a network of cytoskeleton

physical isolation - separated it's internal contents from the external environment

regulation of exchange - as a barrier that can regulate the flow of materials into and out of the cell

communication - between cells and their external environment

Plasma Membrane Proteins

integral membrane proteins - tightly attached to the membrane

peripheral membrane proteins - loosely attached to the membrane

Integral Membrane Proteins

lipid-anchored proteins - membrane proteins that insert themselves into either side of the cell membrane; covalently bounded to lipid tail within the lipid bilayer

transmembrane proteins - span the entire lipid bilayer and protrude into both the cytosol and extracellular fluid; function as a channel for the transport of specific substances across the biological membrane

Peripheral Membrane Proteins

membrane proteins that are loosely attached to either the polar head or other membrane proteins

Membrane Proteins Function

ion channels - form pores that allow specific ions to pass through

receptors - serve as cellular recognition sites where each type of receptor recognizes and binds a specific type of molecule

carriers/transporters - selectively moving a molecule or ion across the membrane

enzymes - catalyze specific biological reactions either inside or outside the cell

linkers - anchor plasma membrane of neighbouring cells to one another

cell-identity markers - to identify whether a cell is one of its own or foreign