Physiology: Transport

Front 1

What equation describes the magnitude of net flux across a membrane?

Back 1

Flux = J = PA(Co - Ci)
Where A = surface area of mem, Co-Ci = diff in conc across mem, P = membrane permeability coefficient.

Front 2

Electrochemical gradient

Back 2

The combined driving force created by the concentration difference (chemical) and the electrical difference/membrane potential (electro). e.g of Na+, K+

Front 3

What are the 3 types of gated membrane channels? Give an example of each.

Back 3

Ligand gated, e.g FINISH Voltage gated, mechanically gated

Front 4

Explain the need for mediated transport systems (i.e transporter proteins)

Back 4

Molecules such as amino acids & glucose are too polar to pass through the lipid bilayer and too large to diffuse through ion channels. Also some ions must be transported actively.

Front 5

Why doesn't facilitated diffusion of glucose into cells result in an equal concentration inside as extracellular?

Back 5

Glucose is metabolised to Glucose-6 phosphate almost as quickly as it enters. This mantains a steep concentration gradient for continued facilitated diffusion

Front 6

What distuinguishes Primary Active transport from secondary?

Back 6

Primary involves energy from ATP. secondary gets its energy from an electrochemical gradient accross a plasma membrane. e,g The Na+/Glucose symporter

Front 7

What would happen to the Na+/glucose secondary transport system if the activity of Na+/K+ ATPase was inhibited?

Back 7

The cell would no longer be able to mantain the Na+ concentration gradient. Because the secondary transport system depends on this gradient for its energy it would fail.

Front 8

Describe and give an example of receptor mediated endocytosis

Back 8

The process by which cells can specifically take up molecules that bind to receptor proteins on the outer surface of the membrane. These recognise the ligand with high affinity. Cholesterol uptake occurs in this way