Cell Physiology and Membrane Transport

Question 1

Why does movement of things need to happen?

Answer 1

Homeostasis requires moving things around like food and O2
-also moving chemicals and electrical signals

Question 2

Why is the plasma membrane selectively permeable?

Answer 2

Due to the combination of phospholipids and proteins

Question 3

What is diffusion

Answer 3

Random thermal motion of a molecule

Question 4

How do molecules move during normal diffusion?

Answer 4

They move to lower concentrations until everything is spread out equally

Question 5

True or False; molecules that go through membranes will always be able to move back and forth, but the netflux will always be up the concentration gradient

Answer 5

Fasle; first part is true but the net flux will be down the concentration gradient

Question 6

In Ficks Law: Rate of Diffusion (J) what do the letters mean in the equation?

Answer 6

P= permeability
A= membrane surface area
Delta C= concentration gradient across the membrane
T= temperature
MW= moleculae weight of the diffusing substance
Delta x= membrane thickness or distance over which the subtsance must move

Question 7

What can easily move through the membrane

Answer 7

hydrophobic- non polar or lipids and very small polar molecules

Question 8

What cannot move easily through the membrane

Answer 8

Hydrophilic substances like charges ions or large polar molecules (they need help)

Question 9

How do ion channels form?

Answer 9

1. there is a linear sequence of amino acids and it inserts itself into the membrane and start to assemble sub units
2. the subunits fold and a water filled hydrophilic pore forms
3. The type of amino acids in the sequence determines selectivity