Cell Physiology Flashcards
Lecture 2,3,4
Plasma Membrane functions
Helps maintain composition of intra- and extra cellular fluids
- forms a framework for protein components of cell
- detects chemical messengers at cell surface
- links adjacent cells together
what regulates what goes in and out of cells
Plasma membrane regulates traffic in and out of cells
what links cells together
plasma membrane
What does a tight membrane junction do?
They are very strong junctions that make an impermeable barrier
Desmosomes
connect certain cells together, they are considered adherence junctions and anchor things together
Gap junctions
for communication btw cells
Permeability of Hydrophobic molecules
Hydrophobic molecules such as O2, CO2, N2 can easily cross the membrane, lipids can also easily cross the membrane
permeability of small uncharged polar molecules
can cross the membrane, not necessarily nonpolar but if molecule is small enough it can cross
permeability of large uncharged polar molecules
can not cross the membrane alone
permeability of ions and charged polar molecules
do not pass through the membrane need special transport to cross the membrane
What are electrochemical gradient?
gradients can be chemical, electrical, or both ie electrochemical. These gradients are a form of energy storage
what are the 4 ways molecules can move across the cell membrane?
- simple passive diffusion
- Facilitated Diffusion
- Active Transport
- Bulk Transport
which types of cell movement require energy?
Active transport and bulk transport
what can affect the rate of diffusion
temperature, movement, and surface area
flux
flux is a measure of diffusion rate
what is net flux
the different btw the two one way fluxes. the net flux will be in the direction of the greater flux, it measures the net gain of molecules by one side and the net loss from the other
Passive diffusion
movement of molecules due to the intrinsic kinetic energy of molecules, not ATP is used, it is just a movement of molecules from a higher concentration to a lower concentration
In passive diffusion what does the direction and magnitude of the net flux depend on?
Permeability, concentration gradient, temperature, surface area, size of molecule, distance
how does water pass through the plasma membrane?
by both simple and facilitated diffusion
what is osmosis? and how is it done?
passive transport of water, net diffusion of water from a region of high water concentration to region of low water concentration. it is facilitated by aquaporins
what determines the direction of water movement in osmosis?
direction of water movement is determined only by a difference in total solute concentration and not by types of solutes
what is osmolarity
total concentration of solutes in a solution, it depends on the total number of molecules not the individual type
Isosmotic
solution is in equilibrium
hyperosmotic
over saturated, cell shrinks
Hyposmotic
low concentration, cell swells
Mediated transport systems
Molecules that are too large and/or polar to diffuse are transported across plasma membrane by mediated transport mechanisms
What are examples of mediated transport systems?
Facilitated diffusion, active transport, bulk transport
Facilitated diffusion
facilitated diffusion is a type of passive transport that allows substances to cross the cell membrane with the assistance of special membrane proteins. ATP is not required, instead facilitated diffusion relies on the concentration gradient of substances being transported
examples of transport protien
channel proteins and carrier proteins
Hyperpolarization
K+ moves out of the cell the magnitude of the membrane potential increases
specificity of channels
specificity depends on charge and pore size
facilitated diffusion by channel proteins
channels provide corridors for polar or charged molecules to pass through the plasma membrane
selectivity of ion channels
can be selective or non selective
constitutive channels
channel proteins that are always open, you have to block them or take them out if you don’t want things to go through
Gated channels
open in response to a trigger
these can be ligand gated channels, voltage gated channels or mechanically gated channels
Ligand Gated channels
when there is ligand is present the channels are open
voltage gated channels
a change in charge is what opens the gate, these gates are regulated by the electrical state of the cell
Mechanically gated channels
these channels are regulated by a physical change, an example of this would be a change in pressure would open the gate
facilitated diffusion by permease/ carrier proteins
permease/carrier binds the substrate, undergoes a confirmation change and releases substrate to the other side. ATP is not needed, transport down the concentration gradient by carrier proteins
Glucose Transporter Proteins (GLUT)
an example of facilitated diffusion via carrier proteins
How do GLUT carrier proteins work
they allow glucose to get through the cell membrane by binding to the GLUT protiens
Active transport
Transported molecules must bind to the transporters, metabolic energy is require.
Primary Active Transport
requires ATP directly
Secondary Active transport
requires metabolic energy indirectly, requires gradient made by atp
in active transport molecules are moved ____ the gradient
up via ATP
what type of transport is calcium pump?
primary active transport
how does the calcium pump work?
atp directly moves calcium out. Hydrolysis of ATP directly required for the function of carrier, the molecule or ions binds to one side of the carrier protein which simulates phosphorylation of carrier protein which then undergoes a conformational change and then the transported molecules are released on the opposite side of the cell.
Na+/K+ is an example of what type of transport
Primary active transport- an exchanger
how does Na+/K+ pump work?
actively exports 2 Na+ out and important
