Understanding Prokaryotic Cell Differences

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Biology › Understanding Prokaryotic Cell Differences

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1

A special dye bonds chiefly to the DNA in cells and is used to help visualize DNA under the microscope. After preparing a microscope slide from human intestine epithelium and observing, a researcher notices that there are differences in the concentration of the dye in the cells on the slide; some dye spots are denser or more defined than in other cells. Which of the following represents the most logical conclusion?

There are eukaryotic and prokaryotic cells in the sample

The dye is unable to bond to any DNA due to residual stomach acids and collects unevenly

Procedural error

There could only be Prokaryotic cells in the sample and the unevenness in dye concentration is due to the differing cell density across the microscope slide

None of these

Explanation

Eukaryotes and prokaryotes are distinguished based on a structure called the nucleus. Eukaryotes have a nucleus, which houses their genetic material. Prokaryotes do not have a nucleus; instead their DNA is localized in an area (i.e. it is not membrane bound). So if the researcher were to stain a sample containing both types of cells, the eukaryotic cells would have darker, more defined stains within their cells. This would indicate the presence of a more compacted and localized DNA than that found in prokaryotes.

2

Which of the following is not present in eukaryotes but is present in prokaryotes?

None of the other answer choices

Cell wall

Ribosomes

Cytosol

Plasma membrane

Explanation

It is important to remember that there are multiple types of eukaryotes. All eukaryotes have a plasma membrane, ribosomes, and cytosol since these are fundamental organelles necessary for basic cellular function. Plant and fungi cells, which are eukaryotic, also possess cell walls. Thus, the answer is "none of the other answer choices."

3

Which of the following is not a difference between eukaryotes and prokaryotes?

Prokaryotes do not have a cell membrane.

Prokaryotes have circular DNA.

Prokaryotes do not have membrane-bound organelles.

Prokaryotes have 70s ribosomes, whereas eukaryotes have 80s ribosomes.

Eukaryotic cell DNA is wrapped around histones.

Explanation

Both eukaryotic and prokaryotic cells have cell membranes. However, the prokaryotic cell membrane is surrounded by a cell wall. Prokaryotes have circular DNA, whereas eukaryotic DNA is in chromosomes and bound by histone proteins. Prokaryotes do not have membrane-bound organelles (endoplasmic reticulum, mitochondria, chloroplasts, Golgi bodies, nucleus). Prokaryotic ribosomes are smaller (70s) than eukaryotic ribosomes (80s).

4

Which of the following statements is false?

Prokaryotes and eukaryotes have identical ribosomes

Prokaryotes are smaller in size that eukaryotes

Prokaryotes do not have membrane-enclosed organelles

Prokaryotes do not undergo meiosis

Prokaryotes lack a nucleus

Explanation

Prokaryotes are much smaller in size than eukaryotes. Eukaryotes are known for their membrane-bound organelles, such as the mitochondria, vesicles, and vacuoles. Prokaryotes do not have membrane-bound organelles. Some eukaryotic organisms go through the process of meiosis in order to produce variation for sexual reproduction.

Prokaryotes undergo a different process to reproduce asexually, called binary fission. The DNA of prokaryotes are contained in a circular chromosome called a nucleoid, which is replicated completely. The cell then splits in two, with each having an exact copy of the same plasmid. Prokaryotes lack a nucleus by definition.

The prokaryotic ribosome is smaller, at 70S, while the eukaryotic ribosome is larger, at 80S. The ribosomes also contain different sized subunits. Prokaryotic ribosomes are made of a 30S and 50S subunit to form the full 70S structure. Eukaryotic ribosomes are made of a 40S and 60S subunit to form the full 80S ribosome.

5

Which of the following structures is not found in prokaryotic cells?

Nuclear envelope

Nucleoid

Ribosomes

Cytoplasm

Plasma membrane

Explanation

Prokaryotic cells are defined as cells that lack membrane-bound organelles, such as the nucleus. Prokaryotic cells still have DNA as their genetic material, however it is located in the cytoplasm in a circular structure known as the nucleoid. The nucleoid is unique to prokaryotes because it lacks a nuclear envelope.

Prokaryotic cells have cytoplasm contained inside of a plasma membrane, and often a cell wall. They also have ribosomes in the cytoplasm to carry out protein synthesis.

Eukaryotes are much more complex and have numerous organelles, including the endoplasmic reticulum, Gogli apparatus, lysosomes, and mitochondria.

6

Which of the following cellular structures can be found in prokaryotes?

Ribosomes

Nucleus

Mitochondria

Chloroplasts

Explanation

Much like eukaryotes, prokaryotes are capable of translating their own proteins. Prokaryotes follow the same central dogma as eukaryotic cells, using DNA to transcribe mRNA and using mRNA and ribosomes to build proteins from amino acids. Ribosomes are primarily composed of rRNA, and are not bound by a membrane.

Prokaryotes lack a nucleus, as well as complex membrane-bound organelles such as mitochondria and chloroplasts.

7

Which structures are found in both prokaryotic and eukaryotic cells?

Cell membrane, DNA, ribosomes

Cell membrane, nucleus, ribosomes

Cell wall, circular chromosome, RNA

Cell membrane, DNA, mitochondria

Explanation

The primary difference between prokaryotes and eukaryotes is the presence of membrane-bound organelles. Prokaryotes lack any membrane-bound organelles, including a nucleus, while eukaryotes possess these structures. All cell types have an outer cell membrane, which contains the cytosol, DNA, and ribosomes. Ribosomes are not bound by membranes, and are essential for translating proteins. Both prokaryotes and eukaryotes use transcription to convert DNA to RNA and translation to convert RNA to proteins.

Mitochondria are only found in eukaryotes and are used to produce ATP via oxidative phosphorylation. A circular chromosome is characteristic of prokaryotes, since they lack a nucleus. Both prokaryotes and eukaryotes can have cell walls.

8

Which of the following statements is false with regard to prokaryotic cells?

Prokaryotic cells have nuclei

Prokaryotic cells have ribosomes

Prokaryotic cells have DNA

Prokaryotic cells have cell walls

Explanation

Eukaryotes and prokaryotes split during evolution when eukaryotic cells adapted membrane-bound organelles. These organelles include the endoplasmic reticulum, mitochondria, chloroplasts, Golgi apparatus, and nucleus (among others). Prokaryotes lack all of these structures.

All cells, however, contain DNA and ribosomes in order to synthesize proteins and maintain metabolic processes. Ribosomes are not bound by membranes, and are instead made of ribosomal RNA (rRNA) and proteins. Both prokaryotes and eukaryotes can have cell walls, though the structure and composition of the cell wall can vary.

9

Which of the following is an example of a prokaryote cell?

Bacteria

Mitochondria

Muscle cell in a human

Plant cell

Explanation

Bacteria are prokaryotes, not eukaryotes. Eukaryotes have membrane-bound organelles and an enclosed nucleus. “Mitochondria” is incorrect and it refers to an organelle in eukaryotes. Muscle cells in humans and plant cells are also eukaryotic cells.

10

A fungus is a member of which group?

Eukaryote

Prokaryote

Archaea

None of these

Protist

Explanation

Like other eukaryotes, fungal cells contain a membrane bound nucleus with chromosomes. They also possess membrane bound cytoplasmic organelles such as ribosomes and mitochondria. A prokaryote is a single celled organism that lacks a membrane bound nucleus, mitochondria, or any other membrane bound organelles.

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