Kathryn Poole
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Chapter 1 of the 4th year Mathematical Physiology course at Oxford University

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Kathryn Poole
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Transmembrane Ion Transport

Question 1 of 5

1

Fill the blank spaces to complete the text.

The cell membrane is a separating the cell interior (the ) and from
the extracellular environment. The membrane contains numerous , and is approximately
thick. The most important property of the cell membrane is its : it
allows the passage of some molecules but restricts the passage of others, thereby regulating the
passage of materials into and out of the cell. Many substances penetrate the cellular membrane
at rates reflected by their in a . However, certain
molecules and ions such as glucose, amino acids and Na+ pass through cell membranes much more
, indicating that the membrane proteins .

Explanation

Question 2 of 5

1

Fill the blank spaces to complete the text.

The membrane contains with diameters of about , and protein-lined
pores, called or , which allow the passage of specific molecules. Both the intracellular
and extracellular environments comprise (among other things) a dilute aqueous solution
of dissolved salts, mainly NaCl and KCl, which dissociate into Na+, K+ and Cl− ions. The cell
membrane acts to the of these ions and to the flow of water.

Explanation

Question 3 of 5

1

Which of the following is an active transport process?

Select one of the following:

  • Osmosis

  • Diffusion

  • Carrier-mediated Transport

  • Carrier-mediated Diffusion

  • ATP hydrolysis

Explanation

Question 4 of 5

1

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Passive mechanisms by which molecules are transported across the cell membrane include
osmosis, diffusion, and carrier-mediated mechanisms. ( Osmosis, Diffusion, Carrier-mediated transport, Carrier-mediated diffusion ), i.e. the diffusion of water down its
concentration gradient, is the most important mechanism by which water is transported across the
cell membrane. Simple ( diffusion, osmosis ) accounts for the passage of small molecules (e.g. Cl−) through
pores and or lipid-soluble molecules (such as oxygen and carbon dioxide) through the lipid bilayer.
( Carrier-mediated diffusion, Carrier-mediated transport ) refers to a process by which a molecule “hitches a lift” by binding to
a carrier molecule which is lipid soluble and can move readily through the membrane. ( Carriermediatedtransport”, Carriermediated diffusion ) occurs when a protein which sits in the membrane has an active site which may
be exposed either on the exterior or interior side of the membrane depending on the conformational
state of the protein. A substrate (e.g. glucose and amino acids) may bind to the protein in one
conformation: the protein then undergoes a ( conformational change, change in concentration, chemical reaction ), and the substrate unbinds on
the other side of the membrane.

Explanation

Question 5 of 5

1

The that exist between the intracellular and extracellular environments
are set up and maintained by active processes. One of the most important of these is the
, which uses the energy stored in to pump out of the cell and in.
Differences in interior and exterior ionic create a across the cell which also drives an ionic current down ion-specific membrane channels

Select option below to complete the highlighted text

    concentration differences
    charge differences
    Na+-K+ pump
    Na+-Ca2+ exchanger
    ATP molecules
    ADP molecules
    the potential difference
    the water-filled pores
    Na+
    K+
    concentrations
    charges
    potentials
    potential difference
    change in concentration

Explanation

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