4) In the fractionation of homogenized cells using centrifugation, the primary factor that determines
whether a specific cellular component ends up in the supernatant or the pellet is
A) the relative solubility of the component.
B) the size and weight of the component.
C) the percentage of carbohydrates in the component.
D) the presence or absence of nucleic acids in the component.
E) the presence or absence of lipids in the component.
5) Which of the following correctly lists the order in which cellular components will be found in the
pellet when homogenized cells are treated with increasingly rapid spins in a centrifuge?
A) ribosomes, nucleus, mitochondria
B) chloroplasts, ribosomes, vacuoles
C) nucleus, ribosomes, chloroplasts
D) vacuoles, ribosomes, nucleus
E) nucleus, mitochondria, ribosomes
6) Green fluorescent protein (GFP) can be used to fluorescently label a specific protein in cells by
genetically engineering cells to synthesize the target protein fused to GFP. What is the advantage of
using GFP fusions to visualize specific proteins, instead of staining cells with fluorescently labeled
probes 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 preserved 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 permits visualization of protein-protein interactions; fluorescent probes do not.
E) GFP fusions are not subject to artifacts; fluorescent probes may introduce background artifacts.
7) What is the reason that a modern electron microscope (TEM) can resolve biological images to the
subnanometer level, as opposed to tens of nanometers achievable for the best super-resolution light
microscope?
A) The focal length of the electron microscope is significantly longer.
B) Contrast is enhanced by staining with atoms of heavy metal.
C) Electron beams have much shorter wavelengths than visible light.
D) The electron microscope has a much greater ratio of image size to real size.
E) The electron microscope cannot image whole cells at one time.