membrane potential

Question 1

the plasma membrane has — that encloses cell and its embedded with — that acts as —-
the head is —-
tails are —

Answer 1

• phospholipid bilayer
  -protein
• receptor/channels
• hydrophilic ( choline phosphate and glycerol )
• hydrophobic ( fatty acids )

Question 2

plasma membrane:
1- all cells are surrounded by —
2- functions:
3- membrane protein includes:

Answer 2

• All cells surrounded by fluid lipid-protein bi-layer
• fucntions:
  1-Forms basic structural barrier enclosing cell
  2-Serves as barrier to free passage of substances
  3-Cell can maintain different mixtures of substances inside and outside (nutrients, waste products)
  4-Fluidity of membrane/cell
  5-Communication between cells
  6-Response to external stimuli
• membrane proteins include:
  1- intergral/ transmembrane
  2- extrinsic / peripheral

Question 3

movement across the plasma membrane
1- Lipid soluble & small uncharged molecules as — are:
— diffusible
- movement is driven by —-
2- charged ( ion) / water soluble:
have — interior of PM which prevents —–
3- the plasma membrane is said to be —-

Answer 3

• freely
• 02
• concentration gradient
• hydrophobic interior
• free movement
• selectively permeable

Question 4

transport across the membrane can be by:

Answer 4

1- diffusion ( (e.g., O2, CO2, lipid (fat)-soluble )
2- Protein-mediated membrane transport by channel or carrier proteins
3- endocytosis ( phagocytoses , pinocytosis )
4- excosytosis

Question 5

separation of opposite charges gives rise to — as opposite charges attract
( diference in cations and actions across PM)
- this can make:
1- — difference across the membrane
2- excitable cells actively induce —-
3- basis for electrical excitability of —–
4- harnessed for —-
- how is this membrane potential done:
- the plasma membrane allows cells to establish difference in —- of key – ions across the pm
- magnitude of potential depends on degree of —-

Answer 5

• membrane potential ( all cells have membrane potential )
  1- electrical
  2- induces change
  3- nerve and muscle
  4- transporting substance
• concentration
• charged ions
• degree of charge separation

Question 6

1-absence of membrane potential leads to —- despite the membrane barrier no charge — across the membrane so no —-
2- presence of membrane potential will have the remained of extra and intracellular fluids —- and —- are responsible for potential

Answer 6

• electrical neutral
• difference
• no membrane potential ( between extra and intracellular)
• electrically neutral
• separated charges

Question 7

• ca is more concentrated —
• k is more concentrated —

Answer 7

• outside
  -inside

Question 8

1-resting membrane potential (RMP):
- Cell membrane is more —- inside than outside
-neuron is about —
2- this is responsible for:
1- —- of k+ , na+ , A- ( large protein anions ) between inside and outside of the cell
2- —– of PM to k+

Answer 8

• negative
• -70mV
• unequal distribution
• selective leakiness
  ( check slide 20)

Question 9

—– establishes K+ & Na+ concentrations across PM , its a — enzyme which transports — out and — in
- uses —- and it takes
- establishes concentration gardietns for —

Answer 9

• Na+/k+ ATPase pump
• membrane spanning enzyme
• 3 na+
• 2 k+
• uses energy ATP (and it takes 200 million ions/sec
• na+ and k+
  ( check slide 22 for graph )

Question 10

RMP concentration:
1- Unequal transport of positive ions by Na+/K+-ATPase also generates —-
2- inside becomes a little – with regards outside bc of –
what is repsonsible for most potential ?
- diffusion of k out of the cell — concentration gradient established by — leaves the inside more —

Answer 10

• small potential
• negatively
• 3na + and 2k+ in
• down
• pump
• negative

Question 11

despite the PM barrier , PM contains many k+ —- which allows the — of k+ at — out of cell – its concentration gradient

Answer 11

• leaking channels
• diffusion
• at rest
• down

Question 12

-K+ leaks out because of — concentration gradient, making inside —-
- —- ) are left behind
further increases inside negativity
- resting membrane potential is —

Answer 12

• large
• -ve
• A- cant pass
• -70mV

Question 13

1—- acts as a driving force for diffusion of K+ out of the cell
2-The residual negative charge acts as a —– drawing K+ back into the cell
3- —-electrical force balances chemical force, no net transport

Answer 13

chemical gradient
electrical driving force
equilibrium

Question 14

nernest equation is :

Answer 14

E = + 61 x log Co/Ci
E = equilibrium potential for ions in mV
61= constant incorporating Gas constant R;
absolute temperature (T), ions valence when the valence is +1: as we have Na+/K+(z), the Faraday constant and logarithmic conversion (natural to base 10) 61 = (RT/zF
Co = concentration ion outside
Ci = cocnetration ion inside

Question 15

—- is concentrated outside cell
—– would “drive” Na+ into cell
plasma merman his very – permable to Na+ bc of —

Answer 15

• na+
• Concentration and electrical gradient
• little
• very few leak channels for sodium

Question 16

Why is the K+ equilibrium potential important?
1- The —- membrane potential is always—- to the potassium equilibrium potential
2-If the membrane becomes permeable to another ion, it will „move toward“ its —-
3- the membrane potential will — as a result
4- if you open a channel for Na+ it will „drive“ the membrane potential toward the ENa+ (i.e. membrane potential will go from —-)

Answer 16

• resting
• close
• change
• equilibrium potential
• negative to positive

Question 17

is a plasma membrane-spanning enzyme and is essential to preserve the ionic gradients across the cell membrane —-

Answer 17

-The sodium-potassium ATPase
- transport :
A. Three Ca2+ ions out of the cell and two K+ ions into the cell
B. Three Cl- ions out of the cell and two Na+ ions into the cell
C. Three Na+ ions out of the cell and two K+ ions into the cell
B. Two Ca2+ ions out of the cell and two K+ ions into the cell
E. Two Na+ ions out of the cell and three K+ ions into the cell

Question 18

membrane potential changes:
1- —- becomes more +ve
2- — become more -ve membrane potential
3- — restores the potential

Answer 18

• depolarisation
• hyperpoliersation
• repolrisaion ( check graph )

Question 19

—- IS THE MAJOR DRIVING FORCE FOR TRANSPORT PROCESSES ACROSS MEMBANES

Answer 19

-NA-K pump
- Cell „cashes in“ chemical gradient of Na+ to transport substances into cell
-Cotransporters
e.g. Na+-Glucose cotransporter
- exchangers : Na+-Ca2+ exchanger

Question 20

classes of ion channels:
1- leak channel as
2- voltage gated channel as:
3- ligand gated channel as

Answer 20

• k+ leak channel
• Voltage-gated sodium-
  channel (VGSC)
• . Acetylcholine receptor