Week 2 Membrane Transport Lecture

Question 1

What is passive transport? what are three types of passive transport?

Answer 1

movement down a concentration gradient that does not require energy input. Simple diffusion, ion channels, facilitated diffusion

Question 2

What is active transport? what are two types of active transport?

Answer 2

movement against a concentration gradient. primary active and secondary active transport

Question 3

What is Fick’s law? what type of membrane transport does it apply to?

Answer 3

Net flux=((Kp)(A)(deltaCs))/(deltaX)

Kp: solute partition coefficient’
A: area
x: thickness
deltaCs: solute concentration gradient

Simple diffusion

Question 4

As thickness increases, net flux…

Answer 4

decreases

Question 5

As the partition coefficient, area, and concentration gradient increases, net flux…

Answer 5

increases

Question 6

Describe simple diffusion

Answer 6

movement across a membrane without the aid of energy or transport proteins

Question 7

The partition constant of simple diffusion is directly proportional to _____ and inversely proportional to _____

Answer 7

directly to lipid solubility

inversely to size of solute

Question 8

rank the permeability of the following: CO2, glucose, Na+, water

Answer 8

Highly permeable: CO2
low permeability: water
almost no permeability: glucose
not permeable: Na+

Question 9

What is pulmonary edema?

Answer 9

accumulation of fluid in the interstitial space

Question 10

High altitude pulmonary edme: cause

Answer 10

low oxygen content @ high altitude is compensated for by increased blood flow. This increases NFP which causes net filtration at capillaries and the accumulation of interstitial fluid. The increased interstitial fluid decreases oxygen diffusion from alveoli to the lungs

Question 11

What are the intracellular and extracellular concentrations of: Na, K, Ca

Answer 11

Na+: 140 mM ext, 10 mM intra

K+: 4.5 mM ext, 140 mM intra

Ca2+: 2-3 mM extra, 0.1 uM intra

Question 12

What type of gated ion channels are there (3)? how do they open?

Answer 12

ligand gated: activated by binding of a chemical signaling agent

voltage gated: activated or inactivated by changes in the membrane potential

mechanically gated: activated by physical deformation of the surrounding plasma membrane

Question 13

rank the speed of transport of: simple diffusion, ion channels, facilitated diffusion

Answer 13

ion channels>facilitated diffusion>simple diffusion

Question 14

How does glucose cross the plasma membrane?

Answer 14

Via facilitated diffusion using the GLUT transporter protein.

Question 15

the GLUT transporter has how many transmembrane domain?

Answer 15

12 transmembrane domains

Question 16

what is primary active transport?

Answer 16

movement against a concentration gradient with the use of ATP

Question 17

what % of total cell ATP does the N/K-ATPase use?

Answer 17

30%

Question 18

What is the most well known example of a primary active transport protein?

Answer 18

Na/K ATPase

Question 19

What is secondary active transport?

Answer 19

uses the energy released from pushing a molecule (Na) down its concentration gradient to pump another molecule against its concentration gradient

Question 20

What are three examples of symporters that utilize secondary active transport?

Answer 20

Glucose/Na, AA/Na, and Cl/K/Na symporters (all pump inside of cells)

Question 21

what are two examples of antiporters that utilize secondary active transport?

Answer 21

H/Na, and Ca/Na antiporters. H and Ca are pumped out of the cells.

Question 22

Which types of transport experience saturation?

Answer 22

any that involve a protein (except ions because that one is just a pore) so Facilitated, prim active, and second active transport.

Question 23

what are the “sides” of an epithelial cell?

Answer 23

apical/luminal side: faces the lumen

Basolateral side: faces the blood vessels

Question 24

secretion refers to movement:

Answer 24

from the blood to the lumen

Question 25

reabsorption refers to movement:

Answer 25

from the lumen to the blood

Question 26

Define transcellular

Answer 26

movement through a cell

Question 27

define paracellular

Answer 27

movement not through a cell

Question 28

how does water flow through a membrane?

Answer 28

passively

Question 29

define osmosis:

Answer 29

diffusion of water across a selectively permeable membrane from high concentration of water to low concentration of water

Question 30

hyper-tonic means

Answer 30

high solute concentration

Question 31

hypo-tonic mean

Answer 31

low solute concentration

Question 32

how do you calculate osmolality?

Answer 32

mOsm=n(deltaC)

n: number of particles/moles
deltaC: concentration in mM

Question 33

what is the normal osmolarity of a cell?

Answer 33

300 mOsm

Question 34

if a cell is placed in a hypotonic soln what occurs?

Answer 34

cell will swell

Question 35

what are aquaporins?

Answer 35

a water channel (not present in all cells)

Question 36

how many aquaporins does a typical RBC contain?

Answer 36

200,000

Question 37

what are three causes of edema?

Answer 37

higher than normal blood pressure, lower than normal protein content in blood, lymphatic obstruction

Question 38

Cells in our body are in _____ equilibrium but in _____ AND _____ disequilibrium

Answer 38

osmotic equilibrium (300 mOsm in and out)

chemical and electrical disequilibrium (different concentrations of solutes inside and outside, more negative inside the cell -70 to -90 mV)

Question 39

define Nernst equilibrium potential

Answer 39

the membrane potential in which a certain ion would not move into or out of the cell

Question 40

which ion largely maintains the resting membrane potential?

Answer 40

potassium ion. it is a positively charged ion with a Nernst potential of -98mV. This means that at normal resting potential, K+ leaves the cell. A loss of positive cells creates a net negative. Usually about 95% of potassium channels are open.

Question 41

in normal cellular conditions (-70mV) are any ions at their Nernst equilibrium?

Answer 41

No, this means that Na, K, Ca and Cl move across membrane