Module 3.3: Transport across the Plasma Membrane
phagocytosis steps
(1) A particle such as a bacterium binds to a receptor in the phagocyte's plasma membrane. (2) This binding triggers the cell to extend bulging "arms" called pseudopods that surround the bacterium. (3) The pseudopods merge to form a transport vesicle that pinches off from the cell surface into the cytosol, becoming a relatively large structure called a phagosome (4) The phagosome eventually fuses with an organelle called a lysosome that contains enzymes that digest the bacterium (lysosomes are discussed in Module 3.4). [consider these just notes- i haven't thought of a good way to make these into cards] {also- think of a creative way / mnemonic to remember all this}
Three variables determine how substance is able to move across plasma membrane by passive or active transport:
(1) Type of substance (2) Plasma membrane permeability to substance (3) Concentration of substance in cytosol and ECF
Water can cross the plasma membrane in two main ways:
(1) through water channels called AQUAPORINS (2) DIRECTLY through phospholipid bilayer
Steps of pinocytosis
(4a) Parts of the endosome may return to the plasma membrane, where they are re-inserted. (4b) Other parts may fuse with a lysosome, where their contents are degraded. (4c) Finally, some parts may exit from the other side of the cell in a process called transcytosis, which we'll cover soon. [consider these just notes- i haven't thought of a good way to make these into cards] {also- think of a creative way / mnemonic to remember all this}
***is dehydration, sports drinks, and water section really necessary??*
(just a question)
are figure 3.18 and its related questions important??
(just asking)
*please view study boost*
(look at it please lol)
see figure 3.10
(please do lol)
please see figure 3.11
(please see it)
Pump maintains steep concentration gradients by transporting _______ out and _______ into cell (against concentration gradients) for every .....
3 Na+ ; 2K+ ; ATP molecule hydrolyzed
what kind of process do vesicles use?
Active transport
Na+ concentration is ten times greater in .....
ECF than in cytosol
Active transport processes require energy (ATP) to proceed as solutes move ______________ concentration gradients (low to high concentration) [PLEASE MAKE SURE YOU ARE NOTICING WHEN IT'S LOW TO HIGH OR HIGH TO LOW FOR THIS CHAPTER]
against
Diffusion is defined as the movement of solute molecules (those that are dissolved) from...
an area of higher solute concentration to an area of lower solute concentration
this separation of charges or electrical gradient is known as...
an electrical potential
The major primary active transport pump in the body is the ____________ pump known as the sodium-potassium pump, or Na+/K+ pump (also called the Na+/K+ ATPase)
antiport
type of pump that transport two or more substances in opposite directions through membrane
antiport
Most water that crosses the membrane does so through....
aquaporins (channels)
review: movement of solute across plasma membrane from higher solute concentration to lower solute concentration
diffusion
review: movement with the concentration gradient
diffusion
there are two basic types of passive transport:
diffusion and osmosis
Small amounts of water cross the membrane...
directly through the phospholipid bilayer
A solute is said to move _______ or "_______" its concentration gradient (from a higher to a lower concentration) during the process of diffusion.
down; with
Separation of charges creates ___________ ____________
electrical gradient
the study of membrane potentials is called
electrophysiology
Extracellular fluid, large molecules, and even sometimes whole cells are taken into the cell by the process of _____________.
endocytosis
the electrical gradient provides...
energy for work
during osmosis, at _________________, concentration of water molecules on either side of membrane is equal; gradient is gone
equilibrium
Exocytosis - large molecules [exit/enter] cell (in other words, they are ????); vesicles fuse with plasma membrane, opening into _______
exit; secretion; ECF
type of diffusion that involves charged or polar solutes (such as ions and glucose) that cross the phospholipid bilayer with the help of a membrane protein.
facilitated diffusion
the enclosure of vesicles in a phospholipid bilayer allows what two things?
fusion with OR formation from plasma membrane or other membrane-bound organelles
in other words, a hypotonic extracellular solution causes a cell to [lose/gain] water
gain
concentration gradients are examples of the...
gradients core principle
force water exerts on walls of its container
hydrostatic pressure
_______________ ECF - solute concentration of ECF is higher than inside cell; more water molecules inside cell than outside; osmotic pressure gradient pulls water out of cell; cell shrinks (crenates)
hypertonic
_________________ ECF has greater ability to cause osmosis than cytosol; cell in hypertonic ECF loses water by osmosis
hypertonic
_______________ ECF - solute concentration of ECF is lower than inside cell; more water molecules in ECF than inside cell; osmotic pressure gradient pulls water into cell; cell swells and possibly ruptures (lysis)
hypotonic
_______________ ECF has lesser ability to cause osmosis than cytosol; cell placed in hypotonic ECF will gain water; cytosol has greater ability to cause osmosis
hypotonic
Generally, smaller particles, particles in the gaseous phase, higher temperatures, and steeper concentration gradients [increase/decrease] the rate of diffusion.
increase
Thin layer of negative charges lines __________ of membrane
inside
the negativity of a resting membrane potential suggests/means that the [inside/outside] of the cell is more negative than the other side
inside (is more negative than ECF)
Normally ECF is _______________ to cytosol
isotonic
what is the tonicity when both fluids have approximately same concentration of solute; no net movement of water across plasma membrane; no volume changes in either fluid compartment?
isotonic
as opposed to the concentration gradient, the actual molecules have [kinetic/potential] energy as long as _________ energy (aka ________) is present.
kinetic; thermal; heat
in other words, a hypertonic extracellular solution causes a cell to [gain/lose] water.
lose
other word for "ruptures"
lysis
term for electrical potential across plasma membrane
membrane potential
Osmosis and diffusion are two fundamentally different forces for three reasons: (1) Osmosis requires presence of __________; diffusion does not (2) Osmosis is _________; diffusion is not (3) Solute movement in diffusion can be predicted by .......................; solvent movement in osmosis cannot [PLEASE MAKE A VENN DIAGRAM OR SOMETHING FOR THIS!!!] [also please, please, please be weary that the first two points here are structured so that diffusion is the latter idea, whereas the last point is the opposite]
membrane; reversible; Fick's diffusion law
the mV value of a resting membrane potential is always [positive/negative]
negative
does passive transport require expenditure of energy?
no
in secondary active transport, ATP is used to create and maintain concentration gradient of ____ substance(s) ....Moving this/these substance(s) across plasma membrane down concentration gradient provides energy to move... [as an analogy: think of a random act of kindness—a person driving through a toll booth on a highway pays for both her toll and the toll of the person behind her; the second person gets a "free ride," just like the second substance being transported.]
one; another substance against its gradient
review: movement of solvent across plasma membrane from area of lower solute concentration to area of higher solute concentration
osmosis
Thin layer of positive charges lines ______________ of membrane
outside
Substance may cross plasma membrane in several ways:
passive transport and active transport
"cell eating"
phagocytosis
endocytosis for particles
phagocytosis
when cells ingest large particles like bacteria or dead or damaged cells or parts of cell
phagocytosis
There are two basic types of endocytosis:
phagocytosis and pinocytosis
vesicles are enclosed in....
phospholipid bilyaer
"cell drinking"
pinocytosis
endocytosis for droplets of fluid
pinocytosis
Diffusion allows solutes to move into and out of the cell using the [kinetic/potential] energy of a concentration gradient.
potential
Osmotic pressure - driving force exerted by solute molecules; causes water molecules to move until equilibrium reached; pressure applied to solution to ____________ water from moving into it by osmosis
prevent
A type of active transport in which ATP is DIRECTLY expended to move a substance against its concentration gradient using a protein pump.
primary active transport
Both primary and secondary active transport processes use plasma membrane carrier proteins called....
pumps
there is one special form of pinocytosis called....
receptor-mediated endocytosis
where receptors fill vesicles with specific molecule (cholesterol, hormones, iron)
receptor-mediated endocytosis
Resting membrane potential - membrane potential when cell is at __________; measured in ____________
rest; millivolts (mV)
Isotonic ECF has _____ ability to cause osmosis as cytosol; [what???] happens when cell is in isotonic ECF
same; no net water movement
read the following: 1 A Na+/K+ pump creates a concentration gradient of sodium ions: 1a Sodium ions from the cytosol bind to the Na+/K+ primary active transport pump. 1b ATP is hydrolyzed, and sodium ions are transported out of the cell, into the ECF, against their concentration gradient. 2 A symport carrier protein uses the potential energy of the sodium ion gradient to power the transport of glucose: 2a From the ECF, both a sodium ion and a glucose molecule bind to a symport carrier protein. 2b The symport carrier protein transports the sodium ion and glucose molecule into the cell—the sodium ion with its concentration gradient and the glucose molecule against its gradient. what type of transport is this?
secondary active transport
type of active transport that uses ATP INDIRECTLY to fuel transport pump
secondary active transport
Phospholipid bilayer is [???]; allows certain molecules to cross; prohibits passage of other molecules; critical to survival of cell
selectively permeable
type of diffusion that mostly involves nonpolar solutes (such as hydrocarbons and lipids, and gases such as O2 and CO2) that pass straight through the phospholipid bilayer without assistance from a membrane protein.
simple diffusion
there are two basic types of diffusion:
simple diffusion and facilitated diffusion
The process of osmosis refers to the movement of ____________, the dissolving medium, across a selectively permeable membrane from a solution with a lower solute concentration to a solution with a higher solute concentration. [note the difference in movement- here it goes from low to high***]
solvent
type of pump that transport two or more substances through membrane in same direction (into or out of cell)
symport
The rate of diffusion depends on several factors, including:
the size and phase (e.g., liquid or gas) of the diffusing particles, the temperature, and the size of the concentration gradient
the passive transport process continues until...
the solute concentration is uniform and EQUILIBRIUM is reached
Just as osmosis leads to volume changes in either side of the container, it can also lead to volume changes in our cells. To understand the type of volume change that occurs, we must examine the concept of ___________
tonicity
Active transport using carrier proteins and channels is effective but has limitations; large polar macromolecules are .................. and the solution to this would be ........
too big to fit; vesicles
[read this carefully! it's not hard, but still...] molecules brought into cell by endocytosis, transported across cell to opposite side, and secreted by exocytosis
transcytosis
type of pump that transport single substance through membrane in one direction (into or out of cell)
uniport
list the three types of pumps in plasma membrane:
uniport, symport, antiport
small sacs filled with large molecules too big to transport by other means
vesicles
an important consequence of osmosis is the change in the ____________ of fluid in each side of our container. These volume changes have important consequences for our __________
volume; cells
usually the solvent in osmosis is...
water
what is tonicity?
way to compare osmotic pressure gradients between two solutions (such as cytosol and ECF)
does active transport require energy?
yes
do solute molecules continue to move around after equilibrium?
yes, due to their kinetic energy
examples of membrane proteins that help with facilitated diffusion:
carriers and channels
__________ separation exists across plasma membrane
charge
The basic force that drives diffusion is called a...
concentration gradient
review: other word for "shrinks"
crenates
K+ concentration is ten times greater in........
cytosol than in ECF
