Module 3.3: Transport across the Plasma Membrane

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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


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