chp 8 10/25/14 Flashcards
Plasma membrane has ____ function.
dual
Plasma membrane prevent ____ of cytosol into the environment
loss
Plasma membrane _____ exchange of substances _____ membrane with the environment.
allow, across
There are ____ categories for the movement of substances through a membrane.
2
What are the two categories for movement of substances.
passive diffusion and active diffusion.
_____ diffusion by an energy coupled transport process
actively
_____ diffusion not triggered by a energy coupled transport.
passively
Name some specific methods by which substances move across membranes
simple diffusion through the lipid bi-layer, facilitated, active transport, simple diffusion through an aqueous protein-lined channel,
_____ is a spontaneous process in which a substance moves from a region of high concentration to a region of low concentration …. eventually eliminating concentration gradient.
Diffusion
What 2 qualifications must be met before a nonelectrolyte (besides chg.) can diffuse passively across a plasma membrane.
1 substance must have a concentration gradient
2 membrane must be permeable to the substance
A membrane may be permeable to a given solute either, because the solute can pass _____ through the lipid layer, because that solute can _____ traverse an aqueous pore that spans the membrane
directly, transverse
Dialysis uses what principle
diffusion
a measure of the polarity (or nonpolarity) of a substance
partition coefficient
Partition coefficient is
the rate of solubility in a nonpolar solvent
in the partition coefficient the more soluble a molecule in the membrane,
the faster it will penetrate the membrane
factors that affect the simple diffusion of a molecule
partition coefficient, size,
the smaller the molecule the ____ it will faster through the membrane
faster
very small uncharged molecules such as ________ are thought to slip between adjacent phospholipids.
O2, CO2, NO, H2O
Larger polar molecules such as ________ have poor membrane penetrability.
sugars, amino acids, and phosphorylated intermediates
_______ is the movement of a molecule across a membrane by the aid of a protein that does not just form a channel but instead binds the ligand and undergoes a conformational change delivering the molecule across the membrane.
facilitated diffusion
_____ is the movement of a molecule across a membrane with a protein that binds and moves it across the membrane.
facilitated diffusion
Proteins that operate in facilitated diffusion are termed ______
transport proteins.
Transport proteins were called
carrier proteins
_____ term applied to some transport proteins that move uncharged molecules like glucose
permease
what is a model of facilitated diffusion?
alternating conformation model
Transport proteins remain in ____ in the membrane and translocates solute by ______ between 2 conformations.
place, alternating
transport protein might bind to solute in one conformation and deposit it on the __________.
other side of the membrane in another conformation
The solute’s binding and release may trigger the transport protein to revert _____
to its original conformation
what is an example of model facilitated diffusion
glucose permease, glut1
concentration outside the cell is 5nm the concentration is
much lower
glucose has a ____ permeability coefficient
low
Facilitating transport proteins share ____ of enzymes
properties
transport proteins are ______ for the solutes they transport.
specific
Transport proteins can be _____ with solute, so a maximum transport rate occurs when all binding sites are occupied with solute.
saturated
The velocity of glucose uptake can be saturated, all the transporters are occupied =
Vmax
Km for D-glucose for this transporter is about ___
1.5 mM
what is Km
measures the affinity of the transporter for glucose
Transporters will also bind other ______ molecules that are similar in structure to D-glucose
6-carbon sugar molecules
What sugars can competitively inhibit the uptake of D-glucose into erythrocytes.
D mannose Km=20mM
D-galactose Km=30mM
The gradient of high glucose levels outside the cell is maintained immediately _____
phosphorylating glucose upon its entering the cell
Some facilitated glucose transporters are regulated by ______ …….like insulin.
hormones
When secreted into the blood stream during high glucose levels, insulin stimulates muscle and fat cells to place more _______ in the plasma membrane.
glucose transporters
a common form of ____ involves mutations that alter the sequences of the transmembrane segments of the transporter preventing transport across the plasma membrane
diabetes
In a ___________ the transport proteins for cysteine and other amino acids is missing from the membrane
kidney disease, cystinuria
carries a only one kind of solute across the membrane
uniport
cooperative channel which moves two substances simultaneously in the same directions, e.g. Na+ and glucose. Due to concentration gradient, Na+ moves downhill and releases enough free energy to move glucose uphill.
symport
exchanges one solute for another by transporting them in opposite directions e.g. cl- for HCO3
antiport
movement of water readily from hypotonic solution to a hypertonic solution. Many cells are much more water permeable than explained by simple osmosis through the bi-layer.
Osmosis
proteins that allow the passive movement of water from one side to the other
aquaporins
The hormone, ____, stimulates water retention by the collecting ducts of the kidney, by way of these channels.
vasopressin
a mutation in this aquaporin channel, in which persons excrete large amounts of urine because their kidneys don’t respond to vasopressin.
congenital nephrogenic diabetes insipidus
Most biological membranes are impermeable to charged substances, including small ions such as
Na+, K+, Ca2+, and Cl-
A variety of proteins termed ______ have been identified
ion channels
The diffusion of ions through a channel is __ ____, from high to low concentration
always downhil
ion channels are ____….. they allow passage of ions in either direction with net flux of the ions depending on the electrochemical gradient
bidirectional
how many ion channes have been discovered
75
what do all 75 ion channels have in common
all are glycoproteins, all have several a-helical membrane-spanning regions, hydrophilic portions protrude into the aqueous cytosol or extracellular matrix
most of the ion channels that have been identified can exist in either an open or closed confirmation such channels are
gated
usually open. allow ions to move back and forth across the membrane without regulation
open channels
gated channels
chemically or ligand gated, usually closed, voltage-gated, mechanically-gated
check out the technique of ________ in studying ion channels
patch clamping
most channels exist in on e of three possible configurations, which is regulated by various stimuli
close, open, inactivated
Voltage Gated Channels fall into what two categories.
multimeric, monomeric
Voltage gated channels that such as the potassium channel, and several protein subunits combine to form the 3-D structure of the transport protein
multimeric
Voltage gated channels fallinto two categories such as the sodium channel one large polypeptide folds into the transport protein having multiple domains
monomeric
a single transmembrane alpha helix in each subunit or in each domain serves a _____ function
sensory
as the membrane potential changes, the S4 _____ shifts in such a way that the channel pore opens.
voltage sensor
S4 can shift and close the channel, making a condition that can quickly re-open when the membrane volatge stimulus reoccurs, termed
channel gating
The movement of ions through the channel results in movement of the cytoplasmic N-terminus domain, termed the ______, into the open pore causing it to be inactivated
inactivating particle
Today there are a considerable number of inherited ion channel diseases named collectively _____, caused by mutation in K+, Na+, Ca2+, and Cl- channels that are known to exist in human and animal models
channelopathies
inside the cell potassium is ____, and inside the cell sodium is ____
high, low
depends on integral membrane proteins that selectively bind a particular solute and move it across the membrane against its concentration gradient in a process driven by eneregy requiring changes in the protein’s conformation
active transport
active transport drives the movement of ions _______
in only one direction
proteins that carry out active transport are often referred to as
pumps
Such _____ movement of ions requires being coupled to an _____ reaction such as: atp hydrolysis, absorbance of light,
endergonic, exergonic
some exergonic reactions
ATP hydrolysis, absorbance of light, transport of electrons, flow of another substance down its concentration gradient.
example of active transport
sodium-potassium pump
termed ______ in nonexciteable cells
membrane potential
termed a ______ in a neurons and muscle cells
resting potential
Cells lining our intestine are able to take up molecules like glucose or amino acids from the lumen into the cells even when the celluar
sodium-glucose symport
_____ seems like active transport, however, the driving exergonic reaction here is the use of the Na+ gradient established by the Na+/K+ pump
sodium-glucose symport
The epithelial lining of the stomack contains a H+/K+ -ATPase which secretes a solution of concentrated acid (up to 0.16 NHCL) into the stomach chamber.
example of transport proteins and medicine
finally the glucose molecules move into the blood stream by _____ through a glucose transporter
facilitated diffusion
mitochondrion basics are _______, meaning they grow and divide within the cell and generate some of the proteins that function there, and take up others from the cytoplasm
semiautonomous
mitochondrion have what
their own dna and ribosomes
how many mitochondrion are in each cell
varies with each cell
space between the membranes is termed ____
intermembrane space
mitochondrion structure infoldings of membrane are termed
cristae
mitochondrion structure solutionwithin inner membrane is termed the _____
matrix
