What are the similarities and differences among ionophores, porins, ion channels, and passive-mediated transport proteins? What determines the direction of solute movement?

Short Answer

Expert verified

Ionophores, porins, ion channels, and passive-mediated transport proteins all follow the same thermodynamic principles.

The concentration gradient controls the direction of solute transport.

Step by step solution

01

Transport protein

A transport protein (also known as a transmembrane pump, escort protein, acid transport protein, cation transport protein, or anion transport protein) is a protein that moves substances, molecules or ions within an organism.

02

Similarities

In the biological system, all transport ions are present (and other substrates).

Biological mechanisms that transfer oxygen, water, and nutrients into cells while also removing waste materials are active and passive transport.

Because active transport involves the transfer of biochemicals from low-concentration areas to higher-concentration areas, it necessitates applying chemical energy.

03

Differences

An ionophore is a chemical compound that reversibly binds ions. As this catalyses ion transport across hydrophobic membranes, ionophore means "ion-carrier."

Porins are beta-barrel proteins that penetrate a cell membrane and serve as a pore for molecules to pass through.

Ion channels are membrane proteins that generate pore-like channels that enable ions to flow through.

Passive mediated transport protein moves ions and other substances across cell membranes without the need for energy.

04

Concentration gradient and direction of solute movement

The concentration gradient is the differential in the concentration of a substance between two regions. The greater the difference, the steeper the concentration gradient and the faster the molecules disperse. However, the solute concentration decreases as it goes from a high to a low concentration.

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Most popular questions from this chapter

BIOINFORMATICS
Brief Exercises Brief, online bioinformatics homework exercises can be
found in WileyPLUS Learning Space.
Exercise 1 Porins: Maltoporin and Ompf
Exercise 2 lon Channels

In addition to neurons, muscle cells undergo depolarization, although smaller and slower than in the neuron, as a result of the activity of the acetylcholine receptor.

(a) The acetylcholine receptor is also a gated ion channel. What triggers the gate to open?
(b) The acetylcholine receptor/ion channel is specific for Na+ions. Would ions flow in or out? Why?

(c) How would the Na+flow through the ion channel change the membrane potential?

Cells in the wall of the mammalian stomach secrete HCI at a concentration of 0.15 M. The secreted protons, which are derived from the intracellular hydration of CO2by carbonic anhydrase, are pumped out by an (H+-K+)-ATPantiport. A co-transporter is also required to complete the overall transport process.

a) Calculate the pH of the secreted HCl. How does this compare to the cytosolic pH (7.4)?

b) Write the reaction catalyzed by carbonic anhydrase.

c) Draw a diagram to show how the action of both transport proteins results in the secretion of HCI.

A certain membrane protein allows phosphate groups to enter a eukaryotic cell.

(a) Would you expect the protein to function more like KcsA or more like GLUTI?

(b) Phosphate ions enter the cell along with ions. Describe this transport system using the terms introduced in Fig. 10-15.

(c) The eukaryotic intracellular pH is typically slightly lower than the extracellular pH. Does this suggest that the phosphate transporter carries out secondary active transport?

In eukaryotes, ribosomes (approximate mass 4×106D)are assembled inside the nucleus, which is enclosed by a double membrane. Protein synthesis occurs in the cytosol. (a) Could a protein similar to a porin or the glucose transporter be responsible for transporting ribosomes into the cytoplasm? Explain. (b) Would free energy be required to move a ribosome from the nucleus to the cytoplasm? Why or why not?

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