Cell Theory and Cell Types Questions and Answers

Answer: D

Correct answer: have a much shorter wavelength than light

An electron accelerated through 100 kV has a wavelength of a few picometres, some hundred thousand times shorter than visible light, and since the diffraction limit scales with wavelength the attainable resolution improves accordingly. In practice lens aberrations keep electron microscopes well short of that theoretical figure, but they still resolve to atomic dimensions.

Answer: A

Passing the beam through reveals internal structure in a very thin slice, while the scanning instrument reflects electrons off a coated surface to give its characteristic three-dimensional appearance. Neither instrument can examine living material.

Answer: B

The first two are correct. The third names the wrong constraint: the limit is set by the need to exchange materials fast enough across a surface that grows more slowly than the volume it must serve, so a cell reaches a ceiling long before its membrane fails mechanically.

Answer: C

A eukaryotic cell of ten to a hundred micrometres dwarfs a bacterium of one or two, which in turn dwarfs a virus of a few tens of nanometres and a ribosome smaller still. The scale spans about four orders of magnitude.

Answer: D

They are bacteria, with no nucleus and no chloroplasts, and they photosynthesise on internal thylakoid membranes instead. The endosymbiotic theory in fact holds that chloroplasts descend from ancestors of this very group of organisms, taken up long ago by an ancestral eukaryote.

Answer: A

Ether-linked membrane lipids and walls lacking peptidoglycan set them apart, and molecular phylogeny places them as a separate domain of life. They remain prokaryotic, having no nucleus, so the difference is chemical and genetic rather than structural.

Answer: B

Both are true and the reason gives the grounds: the differences run deeper than those separating many bacterial groups from one another, and in several respects the archaeal machinery is closer to the eukaryotic than the bacterial.

Answer: C

The genome is common to nearly all the cells, so identity comes from patterns of expression that are established during development and then maintained. This is why a differentiated nucleus can sometimes be reprogrammed.

Answer: D

A single-celled organism is one cell that performs every function of life, which is exactly what the theory claims cells to be capable of. Multicellularity divides those functions among specialised cells rather than changing the principle.

Answer: A

Similarity of cell type and unity of function are both required, which is what distinguishes a tissue from the several tissues that make up an organ. Muscle, nerve, epithelial and connective are the four principal animal types.