Uniporters and ion channels support facilitated transport across cellular membranes. Although both are examples of facilitated transport, the rates of ion movement via an ion channel are roughly 104- to 105-fold faster than the rates of molecule movement via a uniporter. What key mechanistic difference results in this large difference in transport rate? What contribution to free energy (ΔG) determines the direction of transport?

In general, what is the relationship between membrane fluidity and membrane permeability?

Which of the following characteristics may be used to describe Active Transport? Select all that apply. occurs without a transporter protein requires an energy source shows saturation kinetics (has a maximum rate) can occur against a concentration gradient (i.e. uphill)

During an investigation on membrane transport, a researcher exposed bacterial cells to different concentrations of two different solutes: A and B. The rate of transport of each solute into cells isrepresented in the graphSolute ASolute BSolute ConcentrationWhich of the following best explains the greater rate of transport for solute A than for solute B at higher solute concentrations?A Solute A is being transported by simple diffusion, which does not rely on membrane proteins to control the rate of transportSolute A is being transported by active transport, which uses ATP and has higher rates of transport than passive transportSolute A is being transported by facilitated diffusion, which uses membrane proteins to increase the rate of transportRate of Transport

The uptake of l-ascorbate (vitamin C) and its oxidized form, dehydro-l-ascorbic acid (DHAA), was evaluated in brush border membrane vesicles isolated from adult human small intestine. Ascorbate uptake was Na+-dependent and potential-sensitive (Km, 200 umol/L), whereas DHAA transport occurred through Na+-independent facilitated diffusion (Km, 800 µmol/L). If the Vmax of vitamin C import through channels is 401µmol/min/cm2, what import rate would you expect if the lumen contained 133 µmol/L of the version of vitamin C that moves through them?

In the situations described below, what is the free energy change if 1 mole of Na+ is transported across a membrane from a region where the concentration is 48 μM to a region where it is 110 mM? (Assume T=37∘C.) In the absence of a membrane potential.

The following table depicts the rate of transport of a molecule into a cell as the external concentrations are changed. Based on what you know about the characteristics of membrane transport, the molecule is most likely transported by: a) passive transport b) simple diffusion across the membrane c) facilitated diffusion d) active transport

K+ [Select] [Select] A Na+ Primary active transport is being shown by transporter [Select] which uses [Select] ATP [Select] B The transported molecules in this mechanism are being moved [Select] to move Glucose active transport is being shown by transporter [Select] which uses the gradient. Secondary to move against the gradient. When both the molecules move through a transporter in the same direction as in B, this type of transport is called antiport.

Palytoxin is a deadly compound found in certain marine animals. When scientists first isolated palytoxin from sea corals in the 1970s, they did not know how it affected people exposed to it. In time, they began to suspect that the toxin was interfering with the sodium-potassium pump. Researchers have measured the effect of palytoxin on ion transport through the sodium-potassium pump using the patch-clamp technique. This involves using a fine-tipped microelectrode to measure the electric current across pumps in the cell membrane. In this activity, you will examine some of the researchers' results and conclusions. Procedure 1. Read the following observations that researchers made after adding palytoxin to a membrane, and then answer the questions. • Observation 1: The current across a single pump jumped from 0 picoamperes to 1 picoamperes. • Observation 2: When ATP was added to the cytoplasm-facing side of the membrane, the current across a group of pumps increased by a factor of 8…

Compare and contrast the following methods of a passing cell membrane in terms of movement with respect to the concentration gradient, use of ATP, and the use of transporters with examples. (Simple) diffusion vs Facilitated diffusion