Flashcards in Mr. Excitement (pen-jen)- Cell Membrane structure Deck (51):
what is term that defines a bilayer having a polar outer component and nonpolar inner component?
what is a micelle composed of and how is it arranged?
Fatty acid, or single hydrocarbon chains cluster with their polar head groups out and tails towards center
what biochemical structure composes a common bilayer?
phospholipids (they are shaped like cylinders)
what tends to be impermeable to the bilayer?
ionic solutes and large polar solutes
what are the two categories of phospholipids?
what is unique about cholesterol?
it is a sterol with a four ring hydrocarbon
what two molecules are covalently bound in a glycolipid?
carbohydrate and a lipid
what type of fatty acid is known to have "kinks" and what is a unique characteristic of that fatty acid?
unsaturated fatty acid. these types of fatty acids contain double bonds between some carbons, which alters there degree of unsaturation in membrane fluidity
the name implies that glycerophospholipids contain a glycerol backbone, but what other structures are essential for the formation of the lipid?
2 fatty acid tails
a phosphate group (PO4)
the glycerophospholipids are mainly differentiated based on their polar head groups. what are the most common polar head groups that make the phosphatidyl glycerophosolipids different?
ethanolamine, serine and choline
sphingosine has a long hydrocarbon chain that is part of its own structure. but what is unique about the 2nd hydrocarbon tail on sphingosine?
The binding of a fatty acid to the amino group on the sphingosine adds the 2nd hydrocarbon tail common to membrane lipids
in sphingomyelins what two structures tend to bind to the phosphate group?
how do shingolipids and glycolipids compare?
both contain a sphingosine backbone rather than a glycerol backbone
how do sphingolipids and glycolipids differ?
glycolipids contain sugar lipids instead of phosphate groups.
what makes membrane less permeable to small water soluble molecules and water. and also reduces fluidity?
what compound makes cholesterol weakly amphipathic?
The hydroxyl group makes the cholesterol weakly amphipathic, so it fits in the lipid bilayer in a specific orientation, with it’s –OH group towards the polar head groups of the phospholipids
why does viscosity play an important in affecting the functions inside a membrane?
Viscosity of the membrane can affect the rotation and diffusion of proteins and other bio-molecules within the membrane, thereby affecting the functions of these molecules
what 3 things contribute most to membrane fluidity?
lipid composition (cholesterol packing) and hydrophobic tails (saturated vs. unsaturated)
how do long saturated tail affect fluidity?
membrane will be less fluid due to the increase in hydrophobic interactions between the tails and the surface
what type of hydrophobic tails increase fluidity and why?
Short, unsaturated tails result in less surface area for interaction
how do higher temperatures affect membranes?
do sphingomyelins or phospholipids associate into a more solid and thicker bilyaer?
what induces a lipid-ordering effect that stretches the tails?
cholesterol in order to increase thickness
what makes up a flat bilayer?
Lipids with long tails and large head group (cylindrical shape)
what makes up a curved bilayer?
Small heads (cone shape)
what are the 2 layers of the lipid bilayer referred to as?
leaflets (and inner and outer leaflet)?
in which leaflet are carbohydrates most commonly associated with?
the extracellular leaflet
what is the name of movement when a lipid moves from one leaflet to another?
flip-flop movement (if the lipid moves in the same leaflet it is considered lateral movement)
what is common of almost all proteins exposed to extracellular fluids?
they are glycosylated
integral membrane proteins are directly embedded in the bilayer. what 2 types of proteins are classified as integral membrane proteins?
transmembrane proteins and monotopic membrane proteins (partially embedded in the bilayer)
in what conformational orientation are most transmembrane proteins and monotopic membrane proteins embedded into the membrane and why is it significant?
alpha helixes that allows hydrophobic amino acids to interact with the lipid bilayer
what type of protein is covalently attached to hydrophobic fatty acids or prenyl side chains that are incorporated into the lipid bilayer?
lipid linked membrane proteins
how do peripheral membrane proteins associate with other membrane proteins?
associated with other membrane proteins by non-covalent interactions (H-bonds, ionic bonds, van der Waal attractions)
what are the main functions of membrane proteins?
transport, enzymatic activity, cell to cell recognition, signal transduction (Receptors), intracellular joining (gap junctions etc), attachment to cytoskeleton and extracellular matrix.
what are the three main classes of cell binding receptors?
ion channel linked receptors
G-protein couple receptors
enzyme linked receptors
how are ion channel linked receptors opened?
a signal binding molecule (ligand) must bind to signal domain for the protein to have an open conformation. once the ligand binds to the domain than ions can pass thru the channel
what leads to the activation of a lipid-linked G-protein (or GTP-binding protein) on the cytoplasmic side of the membrane?
when bound by specific signal molecule
what happens when a signal molecule binds to an enzyme linked receptor?
undergo a conformational change that “turns on” enzymatic activity on the cytoplasmic side of the membrane
G protein coupled receptors are known to span the membrane seven times. at which cytoplasmic loop do the G-proteins bind?
the third cytoplasmic loop
what type of receptor is the target of most pharmaceutical drugs?
G protein coupled receptors (40%-50% of all drugs)
what is the G protein bound to at rest and what is it bound to when activated?
bound to GDP at rest
bound to GTP when activated
what type of protein is a G protein classified as?
lipid linked protein
what does it mean for a membrane protein or lipid to by glycosylated?
they have sugar group on them
what is the term for the extracellular sugar coat that surrounds lipids and proteins? and why is it important?
glycocalyx. a major role is to protect cells against mechanical and chemical damage.
what type of compound is essential to produce this extracellular sugar coat?
how long are the chains in oligosaccharides
approx 15 carbohydrate chains
oligosaccharides are essential for cell to cell recognition/adhesion. how would they important to the human body?
Recognition of self vs other by the immune system.
They are the distinguishing factor in human blood types and transplant rejection.
do carbohydrates face the cytoplasm?
what organelles in the cell contain carbohydrates?
Endoplasmic Reticulum and Golgi Complex (side that is exposed to extracellular fluid.
what percentage of the membrane is carbohydrate?