Membrane Systems Flashcards
Intracellular fluid is
cytosol
Extracellular fluid is
Interstitial fluid
The ions of higher concentration inside the cell are
K+ and anionic proteins
The ions of higher concentration outside the cell are
Na+
Cl-
Ca2+
Define permeability
The ease with which substances can cross the cell membrane
A cell membrane is selectively permeable and that selectivity is due to
different transport mechanisms
A passive transport mechanism
does not expend energy
An active transport mechanism
expends energy
Diffusion is
passive
random motion of ions and molecules down their concentration gradient
Carrier mediated transport
Can be passive or active
requires transport protein in membrane
When an ion moves from high to low concentration, it is said to be
passive
When an ion moves from low to high concentration, it is said to be
active
Diffusion is define as
the movement of a substance from an area of high concentration to low
Molecules with no electrical charges diffuse
down the chemical concentration gradient
Charged ions and molecules diffuse
based on electro-chemical gradient
What are the four examples of diffusion in body fluids?
O2 moves from lungs to blood
CO2 moves from cells to lungs
Water moves across digestive tract
Anesthetics diffuse into cells
For diffusion to occur, the membrane must be
permeable
The lipid bilayer portion of cell membranes is permeable to
O2
CO2
Hydrophobic molecules
The lipid bilayer portion of the cell membrane is not permeable to
large molecules
hydrophilic molecules
Membrane proteins provide channels for what type of diffusion?
Passive
Define osmosis
Diffusion of water across a semi-permeable membrane in response to solute differences
Water moves
via diffusion down its concentration gradient
In osmosis, water wants to move
from low to high solute concentration
Define osmotic pressure
force of water movement into a solution
Define tonicity
The effects of extracellular solutions on cells
Define isotonic
No net osmosis, no net gain or loss of water
Define hypotonic
Net gain of water into cells
Hypotonic states of cells can result in
Cytolysis (hemolysis in RBCs)
Define hypertonic
Net water flow out of the cell
Hypertonic states of cells can result in
crenation
What is a hypotonic extracellular solution and how will water behave?
Less solutes, more water than intracellular solution
Water will flow into the cell
What is hypertonic extracellular solution and how will water behave?
More solutes, less water than intracellular solution
Water will flow out of the cell
What factors influence diffusion?
Distance
Size
Temperature
Concentration gradient
Diffusion is an effective means of transport from 0- _____ micrometers
123
Diffusion will occur faster if
molecule is smaller
temp is higher
concentration gradient is higher
For charged ions, the 2 driving forces influencing their rate of diffusion are
electrical gradient
concentration gradient
What would happen if a cell suddenly became very permeable to Na+ ions?
Na+ ions would move into the cell
Describe diffusion
Passive
Random motion of substances down their gradient
Channel proteins allow hydrophilic substances through
Describe carrier mediated transport
Passive or active
Requires a transport protein in membrane
Carrier mediated transport relies on what three factors?
specificity
saturation limits
regulation
Define specificity in terms of carrier mediated transport
carrier proteins are generally specific for a particular substance
Define Saturation limits
Rate of transport is subject to number of transport proteins available
Define Regulation
Various control factors exist that effect the activity of carrier proteins
To increase your saturation limit, you can use a
enzyme
Define co-transport
both substances being transported go same directions across the membrane
Define counter-transport
both substances being transported go opposite directions across the memrane
Is facilitated diffusion passive or active?
Passive
Describe facilitated diffusion
Substance moves down conc. gradient
Requires transport protein
Differs from simple diffusion (can reach saturation)
Describe facilitated diffusion with co transport against concentration gradient
One substance moves down gradient
Another moves against gradient
Requires transport protein
Describe active transport
Consumes ATP
Independent of conc gradients
What are the two examples of active transport??
Ion pumps
Secondary active transport
What is trans-membrane potential?
Difference in electrical potential between inside and outside of a cell?
At rest, cells have more negative charge ____ than _____
inside than outside
What is higher in concentration inside a cell at rest?
K+
Proteins (negatively charged anions)
What is higher in concentration outside a cell at rest?
Na+
Cl-
Ca2+
What is the electro-chemical gradient?
Sum of all forces of all chemical and electrical gradients acting across the cell membrane
The resting trans-membrane potential in nerve cells is
-70mV
The resting trans-membrane potential in muscle cells is
-85mV
What is the driving force of ion flow across a membrane?
Diffusion along a electro-chemical gradient
Chemically regulated channels
Open or close when they bind specific chemicals
Voltage-regulated channels
Open or close in response to level of trans-membrane potential
____ is released by motor neurons and tell muscles to contract
ACh
Define neuromuscular junction
synapse between nerve cell and muscle cell
Nerve cell process releases acetylcholine by
exocytosis
Define depolarization
trans-membrane potential becomes less negative
Define hyperpolarization
trans-membrane potential becomes more negative
Define repolarization
trans-membrane potential returns toward resting potential after being depolarized
