Cell Membranes Flashcards
What properties must a cell membrane have?
Flexibility & deformabilitySelective permeabilityFluid environmentReceptorsTransporters, carriers, channelsEnzymesAssociation with cell cytoskeletonJunction and adhesion proteins
Why does a cell membrane need to be flexible?
So that its shape can be altered, for molecules to insert themselves into the membrane
Why do cell membranes need a permeability barrier?
To prevent free movement of ions, solutes (charged particles) into the cell
Why does a cell membrane need receptors?
To recognise hormones, growth factors, neurotransmitters, lipoproteins, transferrin, the extracellular matrix and other molecules.
Why do cell membranes need junction and adhesion proteins?
To link proteins together
True or false? The lipid bilayer is symmetrical.
False. It has an asymmetric structure
True or false? Eukaryotic cells have many membrane systems
True. This is what makes the organelles separate from the cell.
What is the benefit of specialised compartments (membrane-bound organelles) in the cell?
Increased complexity of function
What do complex lipids provide in the membrane?
Plastic, deformable, fluid, dynamic environmentCreates the permeability barrierPlays key roles in signal transduction
What is the role of proteins, glycoproteins and glycolipids in the cell membrane?
Provide receptors, enzymes, junctions with adjacent cellsLinks to the cytoskeleton and extracellular matrixAllow for active transport and carrier functionsPlays a role in signal transduction
How do proteins associate with membranes?
Extrinsically/ PeripherallyIntrinsically/ IntergrallyUsing lipid anchors
What are some functions of membrane proteins?
TransportingLinkingReceptorsEnzymes
What do polar amino acids as part of a polypeptide do in the cell membrane?
Interact with lipid head groups
What is the shape of the main membrane lipids in the bilayer?
Cylindrical
What factors influence fluidity between lipids?
cis-double bonds in fatty acids, acyl chain length, headgroup size, hydration
Complex lipids have a dual affinity. What is the technical term for this?
Amphipathic
What are the benefits of amphipathic complex lipids in a bilayer?
Most favourable arrangement energeticallyVery stable structure (bilayer)
What configuration are most double bonds in unsaturated fatty acids?
Cis
What angle does the cis-configuration of the double bond introduce in fatty acids?
120º
Diffusion rate is proportional to what?
Concentration gradient and hydrophobicity
What does hydrophobicity have to do with the rate at which a water-soluble molecule diffuses across the bilayer?
The greater the hydrophobicity, the faster it diffuses across the bilayer
What molecules cannot cross the membrane on their own?
Polar molecules, large molecules, ions
What are uniporters?
Transporters that move one molecule at a time down their gradient
What are the two types of cotransporters?
SymportersAntiporters
What do symporters/ antiporters do?
Move one or more ions/ molecules down their concentraion gradient with movement of another ion/ molecule against its concentration gradient
What are the three major classes of membrane transport proteins?
TransportersATP powered pumpsChannel proteins
What are transporter proteins?
Bind to one substrate molecule at a time, transports it down it’s concentraion gradient
What are ATP powered pumps?
ATPases that use energy of ATP hydrolysis to move ions or small molecules across the membrane against their concentration/ electrical gradient
How is glucose transported into cells?
Uniporter carries them down a concentration gradient
How are amino acids transported into most cells?
Uniporter carries them down a concentration gradient
What is the electric potential range of animal cells?
-20 to -200 mV
What are the major classes of ATP-powered ion and small molecule pumps?
ABC classF classP classV class
What does the P class ATP pump transport?
H+, Na+, K+, Ca2+
What does the Fclass ATP pump transport?
H+ only
What does the Vclass ATP pump transport?
H+
What does the ABCclass ATP pump transport?
Ions and small molecules
How does signal transduction work?
Seven span receptors in the plasma transduce signals from molecules (that have bound to the receptors). The effects vary from tissue to tissue.
What do the effects of signal transduction depend on?
The receptor type
Why is there a potential across biological membranes?
10% - Na+/ K+ ATPase pump actionMostly - K+ leak channels open; K+flows down itsconcentration gradient leaving negative ions behind
