Classes of membrane transport proteins include all of the following except（）
ATP-powered pumps
B. ion channels
C. protein translocons
D. transporters
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What is the advantage of using GFP-tag to visualize specific proteins, instead of staining cells with fluorescent dyes that bind to the target protein（）
A. GFP fusions enable one to track changes in the location of the protein in living cells; staining usually requires fixed cells
B. GFP fusions enable higher resolution than staining with fluorescent probes
C. GFP permits the position of the protein in the cell more precisely than fluorescent probes
D. GFP fusions are not subject to artifacts; fluorescent probes may introduce background artifacts
All the following statements describe biomembranes except（）
A. Different biomembranes may contain different proportions of the same phospholipids
B. The two leaflets of a biomembrane may contain different phospholipids
C. Some biomembranes have free edges
D. Some phospholipids and cholesterol may cluster to form lipid rafts
The glucose uniporter GLUT1 has a Km of 1.5 mM for D-glucose and 30 mM for D-galactose. At a concentration of 5 mM for each, what is the rate of glucose transport relative to galactose transport？ The
A. 3.7-fold slower
B. equal
C. 5.5-fold faster
D. 20-fold faster
What factors necessary for growth of animal cells in culture are provided by serum（）
A. amino acids
B. precursors of DNA synthesis
C. growth factors
D. vitamins
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