Module 1 Flashcards
describe diffusion in the presence of a membrane, in relation to the membrane’s permeability.
if membrane is permeable to the substance, there will be net diffusion of substance passively down its concentration gradient across the membrane until equilibrium has been achieved
If membrane is not permeable to substance then no diffusion will occur and concentration gradient will remain in place
What is osmosis?
diffusion of water across the plasma membrane
What are aquaporins?
specific membrane proteins that move water
When does osmosis occur?
When membrane separates unequal solutions (different concentrations of water)
- can occur simultaneously with diffusion of a penetrating solute
What is the name of the underlying force that moves water down its concentration gradient?
osmotic pressure
what is hydrostatic pressure?
Force created by given volume of water
- Increased volume means increased hydrostatic pressure
what is facilitated diffusion?
uses carriers to assist transport a substance down concentration gradient
- no energy needed
Describe the mechanism used by facilitated diffusion.
- carrier protein takes conformation in which solute binding site is exposed to a region of higher solute concentration
- solute protein binds to carrier protein
- carrier protein changes shape so binding site exposed to a region of low solute concentration
- transported solute is released and carrier protein returns to conformation from beginning
what is active transport?
Moves substances against their concentration gradient using a carrier protein and ATP or energy
What are the three characteristics of carrier mediated transport?
specificity, saturation, competition
What is vesicular transport?
Transport via a membrane enclosed vesicle and as it uses energy, it is a form of active transport
Describe endocytosis.
Vesicular transport that moves substances from outside to inside of the cell
List the three types of endocytosis.
pinocytosis, receptor mediated endocytosis, phagocytosis
what is pinocytosis?
Cell membrane engulfs and internalizes a small drop of extracellular fluid
- membrane deforming coat proteins on inner side of plasma membrane cause formation of an endocytic pouch pinched off by dynamin, an enzyme that aids in formation of endocytic vesicle
- non selective transport, as vesicle will contain whatever substances were close to membrane at time
- steps: first solute molecules and water molecules are outside plasma membrane, then membrane pockets inward enclosing solute molecules and water molecules, finally pocket pictures off as an endocytic vesicle containing sample of extracellular fluid
What is receptor mediated endocytosis?
Like pinocytosis except trigger to create a vesicle depends on binding of substance to specific receptor on cell surface
- Substances first attach to membrane receptors and then the membrane pockets inward
- finally pinching off as an endocytic vesicle containing the target molecule
What is phagocytosis?
The internalization of large multi molecular particles that only occurs in a few specialized cell types
- first pseudopods begin to surround prey, then they close around prey
- prey is enclosed in endocytic vesicle that sinks into cytoplasm
- lysosome fuses with the vesicle and releases enzymes that attack material inside the vesicle
What is exocytosis?
A membrane enclosed vesicle formed within the cell fuses with the plasma membrane and releases its contents into extracellular environment
- essentially the opposite of endocytosis
- Materials produced by the endoplasmic reticulum and Golgi apparatus use this process for two purposes: to provide mechanism of releasing large polar molecules that can’t cross plasma membrane and it enables cell to move proteins
- release of vesicles is often dependent on the cell receiving a particular signal to release substance
What does it mean for a membrane to be depolarizing?
if magnitude of polarization decreases, moving towards 0 mV
What does it mean when a membrane is repolarizing?
After either a depolarization or a hyperpolarization once the polarizing begins to return towards the RMP or resting membrane potential
Describe a membrane that is hyperpolarizing.
If the magnitude of polarization increases, moving even more negative than the resting membrane potential
What are graded potentials?
Changes in member and polarization used for short distance communication that diminish in strength
what are action potentials?
cause localized depolarization in response to a triggering event or stimulus and can conduct or propagate throughout the entire membrane, not diminishing in strength, which is why they can be used for long distance signalling
What is temporal summation?
summing of several excitatory postsynaptic potentials occurring close together in time due to the repetitive firing of a single presynaptic neuron
What is spatial summation?
summation of excitatory postsynaptic potentials and inhibitory postsynaptic potentials originating from several different person attic inputs having simultaneous effects on membrane potential
