UNIT 2: PLASMA MEMBRANE

Plasma Membrane

the plasma membrane is selectively permeable, allowing only certain molecules to pass

Fluid Mosaic Model

the plasma membrane consists of a “fluid” phospholipid bilayer embedded with a “mosaic” of proteins

Structure of Plasma Membrane

phospholipid bilayer (hydrophilic heads and hydrophobic tails), membrane proteins (integral, peripheral), cholesterol, carbohydrates

Carbohydrates

glycoproteins (attached to proteins) and glycolipids (attached to lipids)

Carbohydrates Structure

short chains attached to proteins and lipids on extracellular side of membrane

Carbohydrates structure

function as signaling “antennae” and cell markers for identification

Membrane fluidity

membranes are not static and temperature affects fluidity; lipids and proteins can shift within the membrane (often laterally)

Cholesterol

type of steroid to regulate fluidity of cell and molecules entering and exiting the cell

Cold Cholesterol

rigid, not as fluid, may break

Hot Cholesterol

too flexible, won’t hold shape

Two Types of Membrane Proteins

integral and peripheral proteins

Integral Proteins

span the membrane or are partially embedded

What do integral proteins include?

includes transport (pumps/channels) and cell signaling (receptor proteins)

What do integral proteins contain?

contains hydrophobic regions (interior) and hydrophilic regions (exterior)

Peripheral Proteins

located on the membrane surface, often attached to integral proteins or cytoskeletal components

What do peripheral proteins serve as?

serve as cell identifiers (antigens) and aid in structural support