Physiology Exam 2

Front 1

Plasma Membranes:

Back 1

-Barrier between ECF and ICF
-Selective permeability

Front 2

What is selective permeability in the plasma membrane?

Back 2

Non-polar and some small polar cross easily (O2, CO2, fatty acids, water, ethanol, urea, steroids)

Large polar molecules and ions can't cross (glucose, proteins, ions)

Front 3

No energy required,
Simple diffusion or mediated transport,
DOWN concentration gradient

Back 3

Passive transport

Front 4

Requires energy,
Requires pumps,
UP concentration gradient

Back 4

Active transport

Front 5

What are the 5 modes of passive transport?

Back 5

1. Simple diffusion
2. Facilitated Diffusion
3. Osmosis
4. Dialysis
5. Filtration

Front 6

Simple diffusion

Back 6

Movement of molecules through the phospholipid bilayer from an area of high concentration to an area of lower concentration (i.e. DOWN the concentration gradient).

Front 7

Simple diffusion

Back 7

-powered by random movement of molecules (Brownian motion)
-diffusions of different substances do not interfere with one another (no competition)
-in general, substances can cross membranes by diffusion if they can dissolve in the hydrophobic (OILY) interior of the membrane
-diffusions can also occur through tight junctions between cells
-does NOT saturate as the concentration or gradient changes

Front 8

In simple diffusion, do molecules/ions stop moving after an equilibrium is reached?

Back 8

NO! There just is no NET movement (net flux).

Examples: H2O, O2, CO2, fatty acids, ethanol, urea, steroids, lipid-soluble vitamins (D,K,E)

Front 9

What are the factors affecting rate of simple diffusion?

Back 9

1. Concentration difference- larger difference or higher concentration, faster
2. Size of molecule- large diffuse slower
3. Temperature- faster at higher temps
4. Surface area of membrane- greater area means faster diffusion (e.g. in emphysema, air sacs of lungs are destroyed so there is less surface area)
5. Thickness of membrane- thinner faster
6. Ability of molecule to dissolve in membrane - lipophilic molecules faster

Front 10

LOOK UP diagrams:

Back 10

Model of simple diffusion,
Magnitude of driving force,
Concentration gradient,
Membrane permeability

Front 11

Facilitated Diffusion

Back 11

Carrier-mediated passive transport

Diffusion of particles through a membrane by means of carrier proteins

Fig. 4-21

Front 12

Facilitated Diffusion

Back 12

-permits flux of substances that cannot diffuse directly through the membrane
-movement is still passive and direction is still from high conc. to low conc.
-saturates when substance reaches high concentrations due to lack of available protein carriers
-related substances CAN compete for the same carrier protein
-specificity between substance and its carrier protein

Front 13

LOOK UP diagrams:

Back 13

Effect of concentration gradient on rate of facilitated diffusion (Fig 4-20, Fig. 4-23)

Front 14

Facilitated Diffusion Model

Back 14

-Affinity of carrier for molecule is same on both sides of membrane
-Molecule binds most to side of greater concentration
(diagram on page 4 of lecture slides)

Front 15

-Transport rate of individual carriers (chemical or electrochemical gradient; affinity for transported substance)
-number of carriers in the membrane

Back 15

Factors affecting rate of facilitated diffusion

Front 16

Facilitated diffusion through ION CHANNELS

Back 16

-open to both intra- and extracellular fluid
a. open (leak) channels- open most of time, free diffusion in both directions
b. gated channels- many are closed most of the time; sensitive to voltage, chemicals (ligands), or mechanical force

Problems with channels can lead to disease: e.g. cystic fibrosis results from mutation in Cl- channel in lungs.

Front 17

Factors affecting the rate of transport through ion channels
1. Transport rate of individual channels

Back 17

-electrochemical gradient
-binding interactions between ion and channel

Front 18

Factors affecting the rate of transport through ion channels:
2. Number of channels in the membrane

Back 18

-open channels
-closed channels

Front 19

Look up

Back 19

Fig. 6-32

Front 20

Diffusion of water across a membrane in the presence of at least one impermeable solute

(Or, diffusion of water across a membrane that limits the diffusion of at least one solute)

Back 20

Osmosis

Front 21

Osmosis

Back 21

-Most membranes freely permeable to water
-Water diffuses from high to love water concentration (high water conc. = low solute conc., low water conc. = high solute conc.)
-water diffuses from low to high solute concentration

Front 22

Osmolarity

Back 22

concentration of solute particles

Front 23

Osmolarity of ICF and ECF=

Back 23

280-296 mOsm (=300 mOsm)

Front 24

150 mM NaCl (~0.9%) = 300 mOsm

150 mM glucose = 150 mOsm

150 mM MgCl2 = 450 mOsm

Back 24

Examples of osmolarity

Front 25

solutions with same osmolarity

Back 25

isosmotic

Front 26

solution with greater osmolarity

Back 26

hyperosmotic

Front 27

solution with lesser osmolarity

Back 27

hypoosmotic

Front 28

the water pressure that develops in a solution as a result of osmosis into that solution

the pressure that must be applied to a solution to just prevent the osmosis

Back 28

osmotic pressure

Front 29

Osmotic pressure

Back 29

greater solute concentration = greater potential osmotic pressure

Front 30

Water flows _____ osmotic pressure gradient.

Back 30

UP. (from low to high osmotic pressure)

*Also remember at equilibrium, there is no net movement of water

Front 31

What is the end result of osmosis?

Back 31

Gain or loss of volume

Front 32

Direction of osmosis can be predicted if:

Back 32

Total solute concentrations are known on both sides

Front 33

What is tonicity?

Back 33

describes behavior of cells when placed in a solution

specifically, related to changes in cell volume

same concept as osmolarity, more related to cells

Front 34

Tonicity of solutions:

Back 34

depends on relative concentrations of non-permeating solutes inside cell and in the solution

Front 35

no change in cell size (equal concentrations non-permeating solutes inside and out)

Back 35

isotonic

Front 36

cell swells (lesser concentration non-permeating solutes outside cell)

Back 36

hypotonic

Front 37

cell shrinks (greater concentration non-permeating solutes outside cell)

Back 37

hypertonic

Front 38

Donnan equilibrium

Back 38

if diffusible solutes are separated by a membrane that is freely permeable to water and electrolytes but totally impermeable to one ionic species, the diffusible solutes become unequally distributed between the 2 compartments.

Front 39

What is reverse osmosis?

Back 39

when pure water is produced by forcing water in impure, waste, or saline fluids through a semipermeable membrane against the water concentration gradient (HYPERFILTRATION)

Front 40

Dialysis

Back 40

Diffusion of small particles, but not larger ones, through a semipermeable membrane; resulting in separation of large and small solutes

Front 41

Peritoneal dialysis

Back 41

1. Dialysis fluid is introduced to the abdominal cavity via the catheter
2. Toxins and water are absorbed by the fluid through the peritoneal membrane
3. The "dirty" fluid is then drained out and replaced with new clean fluid for further dialysis

Front 42

Filtration

Back 42

movement of solutes through a membrane down the hydrostatic pressure gradient

capillaries-tissues
glomeruli-kidneys

Front 43

Active transport properties

Back 43

-move molecule AGAINST electrochemical gradient
-requires energy
-affinity of carrier greater when facing one side of membrane

Front 44

Active transport

Back 44

Primary active transport
Secondary active transport

Other active transport processes:
-Endocytosis (phagocytosis, pinocytosis)
-Exocytosis
-Transcytosis

Front 45

Primary active transport

Back 45

-movement of solute particles from an area of low conc to high conc (UP conc gradient) through PM by means of a carrier molecule that uses ATP DIRECTLY

saturates when substance reaches high concentration due to lack of available protein carrier

Front 46

Primary active transport

Back 46

Carrier protein = ATPase = pump (ATP+Carrier --> ADP+Carrier-P)

Phosphorylation = covalent modulation (changes affinity by changing conformation)

Front 47

Examples of Primary active transport

Back 47

*Na+/K+ pump (NA+/K+ ATPase)*
Ca2+ pump
H+/K+ pump

Front 48

Primary active transport
(sodium-potassium pump)

Back 48

-present in nearly all cells of body
-transports 3 sodium out of cell and 2 potassium into cell per ATP
-electrogenic (net +1 charge out of cell)
-creates conc gradients for sodium and potassium across cell membranes

Front 49

All animal cells:

Back 49

more K+ inside
more Na+ outside

Front 50

Primary active transport
Sodium-Potassium pump

Back 50

1. Transporter binds 3 Na+ from cytosol.
2. Phosphorylation by ATP favors conformationational change.
3. Na+ is released, K+ binds.
4. Dephosphorylation favors original conformation.
5. K+ is released to cytosol. Cycle can repeat.

Front 51

Primary active transport
Ca2+ Pump

Back 51

Located in PM and ER of some organelles

Purpose: to maintain low cytosolic [Ca].....make it very sensitive to any change (Ca is an important signaling ion)

Front 52

Secondary active transport

Back 52

DOES NOT use ATP DIRECTLY but takes advantage of a previously existing concentration gradient, which was created/maintained by primary active transport

Front 53

Secondary active transport... How it works

Back 53

A transport protein couples the flow of one substance to that of another across the PM.
One substance (Na+) moves passively DOWN its electrochemical gradient, in the process releasing energy that is then used to drive the movement of the other substance UP its electrochemical gradient

Front 54

Secondary active transport

Back 54

-one ion moves DOWN conc gradient causing another ion/molecule to move against its conc gradient
-most common ion- sodium
-ATP needed to maintain gradient for ion
-ion acts as allosteric modulator- changes affinity of carrier for molecule to be transported

(2 entities moving through a single protein)

Front 55

What are the 2 types of Secondary active transport?

Back 55

co-transport (symport)

counter-transport (exchange, antiport)

Front 56

Secondary active transport
Co-transporters

Back 56

move 2 or more molecules in the SAME direction

Front 57

Cotransport with Na+ renders substrate transport against its conc gradient energetically ______.

Back 57

favorable

Front 58

Secondary active transport
Counter-transporters

Back 58

move 2 or more molecules in OPPOSITE directions

Front 59

Endocytosis: Phagocytosis

Back 59

taking in solid particles

movement of a cell or large particle into a cell by trapping it in a section of PM that pinches off to form an intracellular vesicle

Front 60

Endocytosis: Pinocytosis

Back 60

taking in liquids

movement of fluid and dissolved substances into a cell by trapping them in a section of PM that pinches off to form an intracellular vesicle

Front 61

Exocytosis

Back 61

Movement of proteins or other cell products enclosed in a secretory vesicle out of the cell by fusing the secretory vesicle with the PM (movement from inside --> out)

Front 62

What are the functions of exocytosis?

Back 62

-add components to PM
-recycle receptors and membrane removed during endocytosis
-secrete specific substance from cell (e.g. protein hormones)

Front 63

Transcytosis

Back 63

involves both endocytosis and exocytosis.

large molecule is taken into an epithelial cell of the intestine by endocytosis, then the intracellular endocytotic vesicle travels to the opposite side of the cell and fuses with the PM to release its content by exocytosis

Front 64

Epithelial transport = transport in the intestine

Back 64

-epithelium- barrier between internal and external environments
-absorption- transport from external environment to internal environment
-secretion- transport from internal environment to external environment
-transport requires movement across 2 membranes

Front 65

facilitated diffusion and cotransport....

Back 65

include glucose

Front 66

in epithelial water transport, active transport of solute is followed by...

Back 66

transport of water (osmosis)