Lecture 1

Question 1

Simple Diffusion

Answer 1

small, lipid soluble molecules and gases (O2, CO2, ethanol, Urea) pass either directly through the membrane or through its pores
(from high to low concentration)
No ATP required

Question 2

Facilitated Diffusion

Answer 2

molecules diffuse across the membrane with the assistance of a carrier protein for the movement of polar molecules- ie: sugars and amino acids (from high to low concentration)
No ATP required

Question 3

Active Transport

Answer 3

move molecules against its concentration gradient
Requires energy from ATP hydrolysis
ATPases (Na+/K+ Pump)

Question 4

Secondary Active Transport

Answer 4

moves molecules against its concentration gradient by using a substance that is transporting along its concentration gradient
Do not require ATP

Question 5

Channel Proteins

Answer 5

pore in the membrane where there is a continuous passage outside and inside. Pore loops create a selectively filter in which only specific molecules can pass through

Question 6

Endocytosis

Answer 6

the inward pinching of membrane to create a vesicle; usually receptor-mediated to capture proteins from outside to inside

Question 7

Exocytosis

Answer 7

partial or complete fusion of vesicles with cell membrane for bulk trans-membrane transport of specific molecules from inside to outside

Question 8

Gated Channels

Answer 8

under certain conditions, the gate is closed and opened (still selective)
The protein components switch between 2 shapes

Question 9

Ligand-gated channel

Answer 9

binding of chemical agent

Question 10

Voltage-gated channels

Answer 10

voltage across the membrane (opens when membrane polarity changes)

Question 11

Exocytosis 1 (Kiss & Run)

Answer 11

the secretory vesicles dock and fuse with the plasma membrane at specific locations called ‘fusion pores’ & can connect and disconnect several times before the vesicle is emptied (usually only partially diffuse- used for low rate signaling)

Question 12

Exocytosis 2 (Full Exocytosis)

Answer 12

complete fusion and total release of contents into the membrane. Used for delivery of membrane proteins and high levels of signalling (process must be counterbalanced with endocytosis to prevent a loose membrane)

Question 13

Depolarization mV

Answer 13

of the membrane to about -50mV no longer provides sufficient electrical attraction to hold the S4 wing downwards so it migrates back up

Question 14

To generate a MP 2 conditions need to be met

Answer 14

1) Create a concentration gradient with an ion pump
2) Semi-permeable membrane

Question 15

NA+/K+ Pump
For each ATP molecule broken down..

Answer 15

• 3 NA+ ions pumped out
  
  • 2 K+ ions pumped in
    Na/K inequality> potential difference of -10 mV (more negative on the inside than outside)

Question 15

Resting Membrane Potential Efflux

Answer 15

this efflux will occur until there is a build up of a + charge on the outside of the membrane that furthers diffusion of K+

Question 16

Resting Membrane Potential

Answer 16

The resting potential in neurons is close to -70mV
- The resting membrane is most permeable to the K+ ion
- K+ diffuses out of the cell along its concentration gradient

Question 17

Equilibrium potential

Answer 17

When the electrical force of repulsion is equal to the chemical force of the diffusion down the concentration gradient

Question 18

Nernst Equation

Answer 18

gives the potential difference across the membrane, inside with respect to outside at equilibrium (result is only valid if and only if one ion species is diffusing across the membrane)