Lecture 5 Flashcards
What is Membrane Permeability?
The net rate of diffusion of a given substance through each unit area of the membrane for a unit [] difference on either side.
What are the 5 factors affecting membrane permeability and why?
1) Membrane Thickness: Increased thickness, decreased diffusion rate
2)Lipid Solubility: Greater solubility, greater diffusion rate (hydrophobicity.. greater increased lipid solubility)
3) Number of Protein Channels: increased rate of transport with greater channel density (# channel/area)
4)Temperature: Diffusion increases in direct proportion with temperature.
5) Molecular Weight of Diffusing Substance; V = velocity of thermal motion (heavier substance will move slower)
What is exocytosis?
Movement from inside to outside of cell
What are the three functions of exocytosis?
1) Membrane Components
- Adds molecules from vesicle interior
- GLUT4 (monosaccharide)
2) Recycle Endocytosis Products (engulf)
- Adds to cell membrane
3) Secretion
- Interior to Exterior
- White blood cells for antibodies
- Neurons… release neurotransmitters
- Mucus…respiratory and digestive systems
What do Junctional Folds do?
Increase SA (membrane tissue)
What do vesicles house?
Neurotransmitters
What is a terminal axon?
A motor axon of motor neuron
What are the three types of transporters?
1) Uniporter
2) Symporter
3) Antiporter
What is a uniporter?
Transports only 1 solute (molecule or ion)
What is a Symporter?
A co-transporter - transport of 1 solute COUPLED to the transport of a SECOND solute in the same direction.
What is a Antiporter?
A exchanger - Transport of 1 solute coupled to the transport of a SECOND solute… in the opposite direction.
What is primary active transport?
- Harness stored chemical energy… ATP
- ATP used directly to move ions.. uphill (against a concentration gradient)
- Na+/K+ ATPase
What is secondary active transport?
Uses stored chemical energy.. ATP indirectly
Harnesses stored electrochemical gradient energy.
What is an example of an ATP pump?
SERCA (Sarco Endoplasmic Reticulum Ca++ ATPase
What are P-type Pumps?
- Phosphorylate themselves during cycle
- Ion pumps for NA+,K+, H+, Ca2+
- Uses ATP
- Primary Active Transport
What is the reaction that happens with a ATP driven pump?
ATP —-> ADP + Pi + E
In SERCA where does the Calcium go?
Calcim is pumped from the Cytoplasm to the Lumen SR (it is stored in very small concentrations in cytoplasm)
What are F-Type Pumps?
- Don’t spend ATP but MAKES ATP
- Turbine-like proteins.. multiple sub units
- Bacteria (plasma membrane)
- Mitochondrion (inner membrane)
What is Membrane Potential?
- Refers to the Electrical energy separation difference across the cell membrane.. sets up the potential to do physical work (i.e, moving ions across the membrane).. measured in Vm (potential difference)
What happens if the Membrane Potential is 0mV?
You have an equal amount of electrical charge on both sides of the membrane
What is Equilibrium in Cell Membranes?
- Combination of electrical and concentration gradients coupled together
- Even balance of ions with no net movement (equal and opposite)
What are the three key points about cell membranes?
1) Small changes in ion concentration induces large changes in membrane potential
2) The difference in electrical charges are close to the membrane.
3) The balance of ions is maintained by active “pumps”
What is the three mechanisms of bioelectrical signalling?
1.) Gated Channels.. membrane embedded proteins
2.) Facilitated Transport..ions move through pores in proteins
3.) Proteins contain gates which exist in 2 states (opened or closed)
What are the 3 types of ion channels?
1) Voltage-gated: electrical environmental determines OPEN OR CLOSED states.
2) Ligand-Gated: a ligand (molecule) binds to an ion channel which opens or closes the gate (example: neurotransmitter)
3) Mechanically-Gated: stretch receptors, requires application of force (mechanical)
What is a Catabolic Rxn?
- Breaking down of structure
- Referred to as “cation”
What does sodium have?
1 lone valence electron that wants to leave causing an electrical imbalance.
