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Ch 7: Membrane Structure and Function - Coggle Diagram
Ch 7: Membrane Structure and Function
Cellular Membranes
Phospholipids
the most abundant lipids in most cell membranes are phospholipids
they are amphipathic meaning they are both hydrophilic (attract water) and hydrophobic (repel water)
most proteins are also amphipathic and they can reside in the phospholipid bilayer
a fluid mosaic is a model that depicts the membrane as a mosaic of protein molecules bobbing in a fluid bilayer of phospholipids
Membrane Proteins
integral proteins penetrate the hydrophobic interior of the lipid bilayer
consist of one or more stretches of nonpolar amino acids
transmembrane proteins are a type of integral proteins that span the entire membrane
peripheral proteins are loosely bounded to the surface of a membrane or to part of an integral protein and are not embedded in the lipid bilayer
some membrane bound proteins are held in place by an attachment to the cytoskeleton
Membrane Carbohydrates
membrane carbohydrates are usually short branched chains that have fewer than 15 sugars
glycolipids are lipids with one or more covalently attached carbohydrates
most membrane carbohydrates are bonded to proteins making them glycoproteins
the diversity of the molecules and their location on the cell's surface enable the membrane carbs to function as markers that distinguish one cell from another
Membrane Structure
Selective Permeability
a property of biological membranes that allows them to regulate the passage of substances across them
the fluid mosaic model helps explain how the membrane regulates the cell's traffic
moves across the membrane in both directions
the cell is able to take up small, non-polar, uncharged molecules
Transport Proteins
transport proteins are hydrophilic tunnels/structure proteins that allow for movement across the membrane
channel proteins have a hydrophilic channel/tunnel that certain molecules or ions can use as a tunnel (moves items across the membrane)
carrier proteins bind to molecules and change shape to shuttle them across the membrane
a transport protein is specific for the substance it translocates allowing only a certain substance
Types of Transport
diffusion is the movement of particles of any substance
concentration gradient is the region along which the density of a chemical substance increases or decreases
active transport requires energy and goes from low concentration to high
passive transport is the diffusion of a substance across a biological membrane with no expenditure of energy, from high to low concentration
osmosis is the diffusion of free water across a semi-permeable membrane
facilitated diffusion is the passage of molecules or ions down their electrochemical gradient across a biological membrane with the assistance of specific transmembrane transport proteins
Bulk Transport
Exocytosis
exocytosis is when the cell secretes certain molecules by the fusion of vesicles within the plasma membrane
when the vesicle membrane and plasma membrane come into contact specific proteins in both membranes rearrange the lipid molecules in both bilayers so that they fuse
this becomes part of the plasma membrane
occurs mostly in eukaryotic cells
Endocytosis
endocytosis is when the cell takes in molecules and particulate matter by forming new vesicles from the plasma membrane
a small area of the plasma membrane sinks inward to form a pocket, then as the pocket deepens it pinches in forming a vesicle containing material that had been outside the cell
phagocytosis is cellular eating
pinocytosis is cellular drinking
Ion Pumps
all cells have voltages across their plasma membrane, which is electrical potential energy
membrane potential is the difference in electrical charge across a cell's plasma membrane, acts as an energy source
electrochemical gradient is the diffusion of an ion which is affected by both the concentration difference of an ion across a membrane
a transport protein that generates voltage across a membrane is called an electrogenic pump
a proton pump actively transports protons (H+ ions) out of the cell