Membrane Transport

Topic 1.4: Membrane Transport

Essential Idea: Membranes control the composition of cells by active and passive transport.

At SHS, Topic 1.4 is taught in the following class unit(s):

Statements & Objectives:

1.4.U1 Particles move across membranes by simple diffusion, facilitated diffusion, osmosis and active transport.

Describe simple diffusion.
Explain two example of simple diffusion of molecules into and out of cells.
Outline factors that regulate the rate of diffusion.
Describe facilitated diffusion.
Describe one example of facilitated diffusion through a protein channel.
Define osmosis.
Predict the direction of water movement based upon differences in solute concentration.
Compare active transport and passive transport.
Explain one example of active transport of molecules into and out of cells through protein pumps.

1.4.U2 The fluidity of membranes allows materials to be taken into cells by endocytosis or released by exocytosis. Vesicles move materials within cells.

Describe the fluid properties of the cell membrane and vesicles.
Explain vesicle formation via endocytosis.
Outline two examples of materials brought into the cell via endocytosis.
Explain release of materials from cells via exocytosis.
Outline two examples of materials released from a cell via exocytosis,

1.4.U3 Vesicles move materials within cells.

List two reasons for vesicle movement.
Describe how organelles of the endomembrane system function together to produce and secrete proteins (rough ER, smooth ER, Golgi and vesicles).
Outline how phospholipids and membrane bound proteins are synthesized and transported to the cell membrane.

1.4.A1 Structure and function of the sodium-potassium pumps for active transport and potassium channels for facilitated diffusion in axons.

Describe the structure of the sodium-potassium pump.
Describe the role of the sodium-potassium pump in maintaining neuronal resting potential.
Outline the six steps of sodium-potassium pump action.
Describe the structure of the potassium channel.
Describe the mechanism of potassium movement through the potassium channel.
Explain the specificity of the potassium channel.
Describe the action of the “votage gate” of the potassium channel.

1.4.A2 Tissues or organs to be used in medical procedures must be bathed in a solution with the same osmolarity as the cytoplasm to prevent osmosis.

Explain what happens to cells when placed in solutions of the same osmolarity, higher osmolarity and lower osmolarity.
Outline the use of normal saline in medical procedures.

1.4.S1 Estimation of osmolarity in tissues by bathing samples in hypotonic and hypertonic solutions. (Practical 2)

Define osmolarity, isotonic, hypotonic and hypertonic.
Calculate the percentage change between measurement values.
Calculate the mean value of a data set.
Calculate the standard deviation value of a data set.
State that the term standard deviation is used to summarize the spread of values around the mean, and that 68% of the values fall within one standard deviation of the mean.
Explain how the standard deviation is useful for comparing the means and the spread of data between two or more samples.
Determine the correct type of graph to represent experimental results.
State that error bars are a graphical representation of the variability of data.
Accurately graph mean and standard deviation of data sets.
Determine osmolarity of a sample given changes in mass when placed in solutions of various tonicities.

1.4.NOS Experimental design- accurate quantitative measurements in osmosis experiments are essential.

Define quantitative and qualitative.
Determine measurement uncertainty of a measurement tool.
Explain the need for repeated measurements (multiple trials) in experimental design.
Explain the need to controlled variables in experimental design.

In the News:

Mouse impervious to scorpion's sting (2013-10-24)
Scientists create endocytosis on demand by 'hotwiring' cells (2017-09-28)
Nobel winners decoded how neurons and cells talk to each other (2013-10-07)
Nobel prize awarded In medicine (2013-10-07)