Membrane Transport Flashcards
What is Osmosis?
It is the net diffusion of water down its own concentration gradient through a selectively permeable membrane
What is Osmolarity?
Its the concentration of osmotically active particles present in a solution. That can be calculated or measured.
Units are Osmoles (Osm) of solute per litre.
What is Tonicity?
Is the effect a solution has on cell volume.
Iso-, Hypo-, or Hypertonic.
What is electrochemical gradient?
The net effect of simultaneous electrical and concentration gradients on this ion. Which contributes to the electrical properties of the plasma membrane
What is facilitated diffusion?
Uses a carrier to facilitate the transfer pf a substance across the membrane ‘downhill’ from high to low concentration
What is Active transport?
Requires the carrier to expand energy to transfer a substance ‘uphill’ against gradient.
What is Primary Active Transport?
Energy is directly required to move a substance against its concentration gradient.
What is Secondary active transport?
Energy is required, but it is not used directly to produce ‘uphill’ movement
What is an example of Primary Active transport?
Sodium Potassium pump
What is the vesicular transport - Exocytosis?
Pinching off of the membrane to engulf the substances
What is the vesicular transport - Endocytosis?
A vesicle fuses with the plasma membrane releasing its contents to the Extra Cellular Fluid
Compare transport rates between carrier-mediated transport and simple diffusion down a concentration gradient
As the concentration of transported molecules in the ECF increases it will eventually level off, which is the carrier-mediated transport concentration gradient (facilitated diffusion). The inital increase before it levels off is the simple diffusion down concentration gradient
What is the type of Lipid Bilayer?
Asymmetry
What is membrane fluidity determined by?
- Lipid concentration
- temperature
- cholesterol content
Why is Asymmetry functionally important?
- unequal distribution of
specific lipids - created by lack of flip-
flopping - allows the cell to have a
different intracellular
environment from the
existing extracellular
environment - signalling proteins bind
to head groups on
inner side - charge asymmetry
How the composition of a membrane affects its properties?
Molecules are able to move around freely (diffuse) within each cellular compartment. However, it is more challenging for some molecules to cross membranes. This is because biological membranes have specific chemical properties, which determine when and how molecules cross the membrane.
What is the Ficj’s Law of Diffusion?
𝑁𝑒𝑡 𝑟𝑎𝑡𝑒 𝑜𝑓 𝑑𝑖𝑓𝑓𝑢𝑠𝑖𝑜𝑛 (𝑄)=(Δ𝐶×𝐴×β)/√(𝑀𝑊×Δ𝑋)
What is integral membrane proteins?
Have membrane spanning alpha-helices which form hydrophobic interactions with lipid tails, contain hydrophobic regions that extend into the intracellular and extracellular environments
What is peripheral proteins?
they are held at the cell surface by polar or charged amino acid R-groups. they have a small number of hydrophobic interactions
What is Diffusion in solution?
Occurs when particles move from an area of higher concentration to one of lower concentration until equilibrium is reached
What is diffusion through a membrane?
a solute can move down a concentration gradient across a semi-permeable membrane, driven by diffusion alone in a thermodynamically favorable process, either by itself, in a process called passive diffusion, or with the assistance of a membrane protein, in a process called facilitated diffusion.
