Urea is a small molecule that is transported out of most cells by passive diffusion, but some cells, including kidney cells, have urea-facilitated transporters
Given an assay to measure the amount of urea on one side of the cell plasma, design an experiment to distinguish which mechanism an uncharacterized cell you have isolated uses to transport urea. Include graphs, if this aids in your discussion.
What will be an ideal response?
Answer: Measure and graph the initial rate of urea transport over a range of urea concentrations. If the rate exhibits saturation kinetics at higher urea concentrations, transport is mediated by a urea transport protein. (To distinguish whether this is facilitated or active transport, it may be necessary to determine whether the urea is transported back out when the external concentration is lowered.) If the import rate increases linearly even at high urea concentrations and does not saturate, the urea transport is by passive diffusion.
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Which of the following describes a haploid?
a. An organism with one set of chromosomes b. A cell with two matched sets of chromosomes c. A cell with a pair of homologous chromosomes d. An organism with double-stranded DNA molecules
An animal has a heart with two chambers and
blood flows in a single circuit. This animal is
a. a salmon. b. a frog. c. a red-winged blackbird. d. a crocodile. e. more than one of these
Which of the following is not an enzyme released from the pancreas?
a. trypsin. b. chymotrypsin. c. pancreatic lipase. d. maltase. e. ribonuclease.