Chapter 5 Membrane Dynamics単語カード | Quizlet

intracellular fluid

2/3 of body fluid

fluid within cells

extracellular fluid

1/3 of body fluid

fluid outside the cell

permeable membrane

a membrane that allows for diffusion of certain solutes and water

freely moving

Semi-permeable membrane

membrane that is selective on what it allows through

ECF:

a lot of Na+, Cl-, Ca+ and very little K+

ICF:

a lot of K+, very little Na+, very little Cl-, very little Ca+

What ions are found in the concentration of ECF and ICF?

osmotic equilibrium

fluid concentrations on both sides of the cell membrane are equal

osmosis

the movement of water across a membrane in response to solute concentration gradient

water moves to dilute more concentrated solution

moves from from high water concentration to low water concentration

meaning ---

water moves from low solute to high solute

once conc. are equal, net movement of water stops

diffusion is constant

net movement/diffusion will stop after concentration equilibrium

Which stops and which continues?

net movement/diffusion or diffusion

osmotic pressure

pressure that must be applied to oppose osmosis

water is constantly moving between cells so the free movement of water between two creates the eq.

Why do the ECF and ICF reach state of osmotic equilibrium?

chemical disequilibrium

the imbalance of chemicals that creates a concentration gradient

electrical disequilibrium

imbalance of charges/ions that can create a membrane potential and an electrical gradient

age: water content decrease as you age

gender: men have a higher % body water than women

% lean body mass: the more lean body mass you have, the more water you have in your body

How does age, gender, and % lean body mass impact body water content?

NO - dynamic steady state

Is homeostasis at equilibrium?

no

Does concentration = volume?

molarity

M = moles/Liter

the number of moles of solute per liter of solution

Osmolarity

molarity (mol/L) X particles/molecule (osmol/mol) = osmol/L

total of particles of solute per volume

290 +/- 50 mOsM (300 mOsM)

What is the normal range of osmolarity in the human body?

compares concentrations in different solutions

# of solute particles dissolved in a volume of solution

looks at both PENETRATING AND NON-PENETRATING SOLUTES

What does osmolarity compare?

Solution A is HYPERosmotic to solution B.

Solution B is HYPOosmotic to solution A.

If solution A has a higher osmolarity (has more solute particles per unit volume, more concentrated) than solution B, what is solution A to solution B? What is solution B to solution A?

compares a solution and a cell by describing the solution

looks at the consequence of concentrations of soltions

looks at ONLY NON-PENETRATING SOLUTES

What does tonicity compare?

Solution A has a lower solute concentration than Solution B

HYPOosmotic means

Solution A has more solute concentration than Solution B

HYPERosmotic means

two solutions contain the same number of solute particles per unit volume

ISOosmotic means

tonicity

Which tells you what happens to a cell when placed into a solution?

tonicity or osmolarity?

hypotonic

NP<300 mOsM

means that the solution is hypotonic to the cell - there is a low concentration of solutes in the solution than inside of cell

cell swells/lyse - gains water

hypertonic

NP>300 mOsM

means that the solution is hypertonic to the cell - there is more concentration of solutes in the solution than inside of cell

cell shrinks/crenate - loses water

1. if the CELL has a HIGHER conc. of NONpenetrating solutes than the solution, there will be net movement of water INTO the cell. The cell swells and the solution is hypotonic.

2. if the cell has a LOWER conc. of nonpenetrating solutes that the solution, there will be net movement of water OUT of the cell. The cell shrinks and the solution is hypertonic.

3. if the conc. of nonpenetrating solutes are the same in the cell and solution, there will be no net movement of water at equilibrium. The solution is isotonic to the cell.

What are the rules for predicting tonicity?

NaCl

if a cell is placed in a solution of NaCl, the Na+ and Cl- ions do not enter the cell.

What is the most important nonpenetrating solute in physio?

bulk flow

most general form of biological transport = (gas or liquid) within a compartment

a pressure gradient causes fluid to flow from regions of high pressure to low pressure.

ex. blood moving through the circ. system.

heart acts as pump that creates region of high P, pushing plasma with its dissolved solutes and suspended blood cells through the blood vessels.

ex. air flow in the lungs

the lipid and protein composition.

permeability is variable and can sometimes be changed by altering the proteins or lipids of the membrane

What determines which molecules will enter and exit the cell?

size of molecule and its lipid solubility

What are 2 factors of molecules that influence its movement across cell membranes?

dissolve easily in a solution

When something is soluble, that means it can do what?

very small molecules and those that are lipid soluble

What types of molecules can cross directly through the phospholipid bilayer?

through vesicles

How do very large lipophobic molecules enter/exit the cells?

movement that doesn't require the input of energy other than the potential energy stored in the concentration gradient

What is passive transport?

movement that requires the input of energy from outside source (ATP)

What is active transport?

- simple diffusion (conc. gradient)

protein mediated:

- facilitated diffusion (conc. gradient)

- ion channel (electrochemical gradient)

- aquaporin channel (osmosis)

What are types of passive transport?

Vesicular transport (ATP)

- exocytosis

- endocytosis

- phagocytosis

Protein-mediated:

- direct or primary active transport (ATPases)

- indirect or secondary active transport (conc. gradient created by ATP)

What are the types of active transport?

- passive transport

- move from high to low conc.

- net movement occurs UNTIL conc. are equal

- rapid over short distance and slow over long dist

- directly related to temp (high temp= fast rate)

- rate is inversely related to molecular weight and size. The bigger the weight/size, the slower the rate

- can take place in an open system or across a partition that separates two compartments

What are some characterisitics of diffusion?

along higher conc. gradients

over shorter distances

at higher Temps

for smaller molecules

When is diffusion faster?

flux

a state of continual change or movement

diffusion rate/unit of membrane surface area

net flux

compares the movement between 2 compartments (movement in both directions)

diffusion equilibrium

movement occurred - equally

so the next flux is 0

yes

When net flux is 0, is there still movement?

- lipid solubility

- molecular size

- concen. gradient

- membrane surface area

- composition of lipid layer

What are some factors affecting the rate of diffusion through a cell membrane?

permeability constant

the permeability of a molecule when given temperature and a particular membrane

flux will increase if either of these increase

because it is too large of a distance.

instead we count on specialized systems for access and long distance transport

Why can't humans rely on simple diffusion from outside the body to cells?

because they can more easily move through the non polar membrane.

O2,CO2, fatty acids, steroids move through well

water is small enough to move through

Why do nonpolar molecules have a higher P through a lipid bilayer than polar molecules?

osmosis - movement of water across membrane

diffusion - movement of water and solutes across a membrane

Compare and contrast osmosis and diffusion.

channel proteins

carrier proteins

What are two types of transport proteins?

channel proteins

create water-filled passageways that directly link the ICF and ECF

allow more rapid transport across the membrane but generally are limited to moving small ions and water

carrier proteins

aka transporters

bind to the substrates that they carry but never form a direct connection between ICF and ECF

slower, but move larger molecules than a channel protein

aquaporin

a water channel that allows water to move in large amounts across a membrane

ion channel

a channel that allows for atoms with a charge (ions) to move across a membrane

Open channels (leak channels)

gated channels that spend most of their time open, allowing ions to move back and forth without regulation

gated channels

gated channels that spend most of their time closed which regulates ions moving through them

- ligand gated: chemical substrate

- voltage: charged ions

- mechanically gated: physical force

uniport carrier

a carrier protein that move only one kind of molecule

cotransport

a carrier protein that moves more than one kind of molecule at one time

symport carrier

a carrier protein that moves molecules in the same direction (in or out of the cell)

antiport carrier

a carrier protein that moves molecules in both directions (in or out of cell)

1. chemical specifity

2. conformation change

3. limited rate of transport

- solute conc. and affinity

- # transporters

- rate of conformational change

- competitors

The binding site of a carrier protein has:

facilitated diffusion

diffusion w/ protein carrier (i.e. sugars, amino acids)

like GLUT transporters, move glucose and related hexose sugars across membranes (usually never reaches equilibrium, almost always have a gradient coming into the cell)

reversible transport depending on concentration gradient.

uses ATP

moves against conc. gradient

moves from low to high conc.

active transport

primary/direct active transport

the energy to push molecules against its conc. gradient comes directly from ATP

secondary/indirect active transport

uses PE stored in the conc. gradient of one molecule to push other molecules against their conc. gradient.

it ultimately depends on primary active transport, because the conc. gradients that drive secondary are created using ATP

because primary active transport uses ATP as the energy source.

ATPases (aka pumps) hydrolyze (breaks down) ATP to ADP and Pi harnessing energy.

Primary active transporters are also known as ATPases, why?

- pumps 3 Na+ (in higher conc. in ECF) out of the cell

- pumps 2 K+ into the cell

Na+/K+ ATPase pump

how much of each is pumped in and out of cell?

Na+: low in cell, high out of cell

K+: high in cell, low out of cell

Na+ conc. is high and low where?

K+ conc. is high and low where?

1. 3 Na+ from ICF bind to high affinity sites

2. ATPase is phosphorylated with Pi from ATP, protein changes conformation

3. Na binding site loses their affinity for Na and releases the 3 Na+ into ECF; high affinity binding sites for K+ appear

4. 2 K+ from ECF bind to high affinity sites; protein changes conformation and Pi is released

5. K binding sites lose their affinity for K and release 2 K into ICF; high affinity binding sites for Na appear.

Mechanism of the Na/K pump

Na+ has leaky channels and follows its concentration and electrical gradient into the cell.

K+ channels open and it follows its concentration gradient out of the cell but is going against its electrical gradient.

Then the Na+/K+ ATPase will restore them back to the correct place and move them both against their concentration gradients.

Be able to explain the action of the Na+/K+ ATPase pump.

How does this pump help to maintain the electrochemical gradient and the membrane potential of a cell?

carrier protein specificity

the ability of the transporter to move only one molecule or only a group of closely related molecules

binding sites have 3D properties

12 known GLUT transporters (GLUT 1- GLUT 12)

each specific GLUT has a higher affinity for a specific monosaccharide hexose sugar.

carrier protein competition and competitive inhibition

similar solutes may be transported by the same protein thus creating competition

GLUT: glucose and other hexose sugars: fructose, galactose, mannose

GLUT: may bind but not transport disaccharides (like maltose) (competitive inhibition) even at the same conc. of fructose and GLUT, if you add maltose you will have inhibition.

carrier protein saturation

transport maximum

# of transporters are saturated with solute

concentration is high

increase solute concentration and expect an increase in amount being moved until you have reached the transport max, plateaus.

Vesicular transport

type of active

transport of macromolecules that are too large to enter or leave through protein channels or carriers.

two types for import into cell:

endocytosis and phagocytosis

out of cell: exocytosis

across cell: transcytosis

Phagocytosis

actin-mediated process by which a cell engulfs a bacterium or other particle into a large membrane bound vesicle called a phagosome.

the phagosome pinches off from the cell membrane and moves to the interior of the cell, where it fuses with a lysosome whose digestive enzymes destroy the bacterium .

requires energy from ATP for the movement of cytoskeleton and for the intracellular transport of the vesicles.

a ligand binds to a membrane receptor protein to activate the process

occurs in regions of the cell memb. called coated pits, indentions where the cytoplasmic side of the memb. has high conc. of protein. (clathrin)

Where does receptor mediated endocytosis occur and what is it?

Epithelial transport

movement between compartments

movement into and out of body must cross layer of epith cells that are connected to one another by adhesive and tight junctions

apical membrane

Which membrane faces the lumen?

basolateral membrane

Which membrane faces the ECF?

absorption

transport of material from the lumen of an organ into the ECF

GI tract absorbs digested nutrient

also respiratory system

secretion

when materials moves from ECF to the lumen

ex: salivary glands secrete saliva to help moisten food

Paracellular transport

movement takes place through the junctions between adjacent cells

not happening much in tight junctions

transcellular transport

movement through epithelial cells

must move across 2 membranes

uses both active and passive transport

ion conc. gradients between the ICF and ECF

the selectively permeable cell membrane

What creates the membrane potential?

2. we insert a leak channel for K+ into the membrane, making the cell freely permeable to K+, so K+ starts to move out of the cell down its conc. gradient so then there is electrical disequilibrium, the ECF has a net + charge and the ICF has a net - charge.

As add'l K ions leave the cell, going down their conc. gradient, the inside of the cell becomes more negative and the outside becomes more +.

1. When we begin the cell has no membrane potential: The ECF and ICF are electrically neutral

resting membrane potential

-70mV

K+ follows its gradient (electrical gradient)

how much K+ will diffuse?

- balance between the [K+] gradient and the electrical gradient.

normally along a conc. gradient it would all diffuse until equ. but because like charges repel and diff charges attract, this will reach a diff kind of balance.

What happens when a K+ leak channel is added?

equilibrium potential

for any given conc. gradient of a single ion, the membrane potential that exactly opposes the concentration gradient

example: when the conc. gradient is 150 mM K+ inside, and 5 mM K+ outside the cell, the equilibrium potential for potassium is Ek = -90 mV.

depolarization

membrane potential becomes less negative

Repolarization

membrane would return to its original state (would become more negative -70)

Hyperpolarization

the membrane goes past its resting potential and is more negative before eventually depolarizing to get back to its original state

Increasing or decreasing ion permeability can cause changes in the membrane potential difference (Vm)

Entry of Ca2+ or Na+ into the cell will depolarize the cell (membrane potential becomes more positive)

Entry of Cl- into the cell hyperpolarizes the cell (makes the membrane potential more negative)

making the cell less permeable to K+ will make the membrane depolarize

produce and store insulin in cytoplasmic secretory vesicles

they secrete insulin when blood glucose levels exceed homeostatic range (after a meal) - 120 mg/dL

- insulin serves as the signal to other cells to take up glucose, bringing blood conc. down to pre-meal levels

they must be able to respond to blood glucose levels that are higher than acceptable range

must be able to translate the change in glucose conc. into cell action

coordination between membrane function and overall cell function

Pancreatic beta islet cells do what?

1. low blood glucose 60-120 mg/dL

2. metabolism slows (low cell. resp.)

- low facilitated diffusion w/GLUT

3. ATP decreases

4. Katp channels open

5. cell at resting membrane potential. no insulin released...voltage gated Ca2+ channel closed

no insulin secretion

Beta cell at rest. what is happening?

1. high blood glucose > 120 mg/dL

2. metabolism increases (high cell resp.)

- high facilitated diffusion w/GLUT

3. ATP increases

4. Katp channels close

5. cell depolarizes and calcium channels open

6. Ca2+ entry acts as an intracellular signal

7. Ca2+ signal triggers exocytosis and insulin is secreted

Beta cell secretes insulin. what is happening?