Question 1

Higher plants and higher animals are similar in that they contain about the same number of different cell types.

Accepted Answer

Higher plants contain many more different cell types than higher animals. For example, in plants, specialized cells include guard cells, trichomes, root hairs, and parenchyma cells, while animals have more limited cell types, such as muscle cells, nerve cells, and blood cells.

Question 2

Epithelial cells form sheets that cover the surface of the animal body and line internal organs.

Accepted Answer

Epithelial cells do indeed form sheets that cover the surface of the animal body and line internal organs.

Question 3

In good culture conditions, E. coli typically divides every two hours.

Accepted Answer

Under optimal conditions, E. coli can divide as rapidly as every 20 minutes, not every two hours.

Question 4

Yeasts are simple eukaryotes.

Accepted Answer

Yeasts are unicellular eukaryotic microorganisms that are classified under the Kingdom Fungi. They are simple in structure compared to complex multicellular eukaryotes.

Question 5

Caenorhabditis elegans is an important organism for the study of plant development.

Accepted Answer

Caenorhabditis elegans is actually an important model organism for the study of various biological processes, such as genetics, development, and behavior. It is a tiny, transparent roundworm that has a fully mapped genome and shares many genes with humans. However, it is not commonly used for the study of plant development.

Question 6

Studies on Arabidopsis thaliana have indicated that the mechanisms that control development in plants are completely different from those that control development in animals.

Accepted Answer

While there are significant differences, studies on Arabidopsis thaliana have shown that there are also fundamental similarities in the mechanisms controlling development in both plants and animals, such as the role of certain signaling pathways and gene expression patterns.

Question 7

The frog Xenopus laevis is useful for studying early development because its eggs are small and clear.

Accepted Answer

Xenopus laevis eggs are actually large and opaque, which makes them particularly useful for manipulation and observation during early developmental stages.

Question 8

Xenopus laevis, an amphibian vertebrate, is useful for developmental studies because when its eggs are fertilized, the embryos develop outside its body.

Accepted Answer

When Xenopus laevis eggs are fertilized, they develop outside the body, making them ideal for studying early developmental processes such as the formation of the neural tube and organogenesis.

Question 9

A single somatic animal cell in culture is capable of forming an entire animal.

Accepted Answer

A single somatic animal cell in culture is not capable of forming an entire animal. It would require additional cellular and environmental factors such as fertilization, cell differentiation, and proper development within an intact organism.

Question 10

Normal human fibroblasts can be grown only for 50-100 doublings in culture, after which they stop growing and die.

Accepted Answer

This phenomenon is known as the Hayflick Limit and is a result of telomere shortening with each cell division. Once the telomeres become critically short, the cells enter senescence and stop dividing.

Question 11

Immortal cell lines are cells that can continue to proliferate in culture for an indefinite number of generations.

Accepted Answer

Immortal cell lines have the ability to continuously divide and proliferate in culture for an indefinite period of time, making them valuable tools in scientific research. Examples of immortal cell lines include HeLa cells and WI-38 cells.

Question 12

A single immortalized fibroblast in culture is capable of forming an entire human.

Accepted Answer

While it is possible to grow human tissues and organs using cells derived from a single fibroblast, it is not possible for a single fibroblast to develop into an entire human as it is only one type of cell and lacks the genetic information necessary for full human development.

Question 13

With appropriate stimulation, mammalian stem cells in culture can give rise to individual mammalian cell types and hence may provide a source of patient-specific replacement cells.

Accepted Answer

Mammalian stem cells have the potential to differentiate into various cell types, making them a potential source of patient-specific replacement cells with appropriate stimulation.

Question 14

Viruses are complexes of nucleic acid and protein that can replicate on their own.

Accepted Answer

Viruses cannot replicate on their own and depend on host cells to replicate. They are not considered living organisms due to their inability to carry out metabolic processes on their own.

Question 15

Viruses can have either RNA or DNA for their genetic material.

Accepted Answer

This statement is true. Some viruses have RNA as their genetic material (called RNA viruses) and others have DNA as their genetic material (called DNA viruses).

Question 16

Synthesis of DNA from RNA was first observed using retroviruses.

Accepted Answer

Retroviruses have RNA as their genetic material and use the enzyme reverse transcriptase to convert their RNA into DNA, which can then integrate into the host genome. This was the first observed instance of DNA synthesis from RNA.

Question 17

Robert Hooke first coined the term "cell" following his observation, with a light microscope, of the pattern of cell walls in cork.

Accepted Answer

This statement is true.

Question 18

Because the wavelength of electrons is 100,000 times shorter than the wavelength of visible light, the resolution of the electron microscope is 100,000 times better than the resolution of the light microscope.

Accepted Answer

The resolution of the electron microscope is significantly better than that of the light microscope due to shorter electron wavelengths, but it is not directly 100,000 times better. The improvement in resolution is substantial but not directly proportional to the wavelength difference.

Question 19

Scanning electron microscopy is usually used for a three-dimensional view of the surface of cells.

Accepted Answer

Scanning electron microscopy uses a focused beam of electrons to scan the surface of a sample and create a three-dimensional image. Therefore, it is commonly used to visualize the surface of cells.

Question 20

Freeze fracture splits lipid bilayers and allows examination of the distribution of proteins that span the bilayer.

Accepted Answer

Freeze fracture is a technique used for examining the ultrastructure of biological membranes, especially lipid bilayers. It involves rapidly freezing a biological sample and then fracturing it to reveal the internal structures. By doing this, the lipid bilayer can be split and the distribution of proteins that are embedded within it can be examined.

Quiz 1: An Overview of Cells and Cell Research