3.2.1.2 Structure of prokaryotic cells and of viruses

What is a key structural difference between prokaryotic and eukaryotic cells?

• Prokaryotic cells have a nucleus.

• Prokaryotic cells lack membrane-bound organelles.

• Prokaryotic cells have larger ribosomes.

• Prokaryotic cells have DNA associated with proteins.

Answer explanation

Prokaryotic cells lack membrane-bound organelles, which distinguishes them from eukaryotic cells that have such structures. This absence is a fundamental characteristic of prokaryotic cell structure.

What type of genetic material is found in prokaryotic cells?

• Linear DNA associated with proteins

• Single circular DNA molecule

• RNA only

• Multiple linear chromosomes

Answer explanation

Prokaryotic cells contain a single circular DNA molecule, which is distinct from eukaryotic cells that have linear DNA associated with proteins. This circular DNA is located in the nucleoid region of the cell.

What is the composition of the cell wall in prokaryotic cells?

• Cellulose

• Chitin

• Murein, a glycoprotein

• Peptidoglycan

Answer explanation

The correct answer is 'Murein, a glycoprotein' because prokaryotic cell walls are primarily composed of peptidoglycan, also known as murein, which provides structural support and protection.

Which of the following is NOT found in prokaryotic cells?

• Plasmids

• Nucleus

• Capsule

• Flagella

Answer explanation

Prokaryotic cells lack a nucleus, which is a defining feature of eukaryotic cells. Instead, their genetic material is found in a nucleoid region. Plasmids, capsules, and flagella are all present in many prokaryotic cells.

What is the function of plasmids in prokaryotic cells?

• Energy production

• Protein synthesis

• Genetic exchange

• Structural support

Answer explanation

Plasmids are small, circular DNA molecules in prokaryotic cells that facilitate genetic exchange. They can carry genes that provide advantages, such as antibiotic resistance, allowing for horizontal gene transfer between bacteria.

What is the role of flagella in prokaryotic cells?

• Photosynthesis

• Movement

• DNA replication

• Protein synthesis

Answer explanation

Flagella are tail-like structures that enable prokaryotic cells to move. They rotate like a propeller, allowing the cell to swim through liquids, making 'Movement' the correct answer.

Which of the following is a characteristic of viruses?

• They have a nucleus.

• They are acellular.

• They have a cell wall.

• They contain ribosomes.

Answer explanation

Viruses are acellular, meaning they do not have a cellular structure like living organisms. They lack a nucleus, cell wall, and ribosomes, which are characteristics of cellular life forms.

What is the protein coat surrounding the genetic material of a virus called?

• Capsule

• Cell wall

• Capsid

• Plasmid

Answer explanation

The protein coat surrounding the genetic material of a virus is called the capsid. It protects the viral genome and aids in the infection of host cells, distinguishing it from other terms like capsule or plasmid.

What type of genetic material can be found in viruses?

• Only DNA

• Only RNA

• Either DNA or RNA

• Both DNA and RNA simultaneously

Answer explanation

Viruses can contain either DNA or RNA as their genetic material, but not both simultaneously. This diversity allows them to adapt and evolve in various environments.

What is the function of attachment proteins in viruses?

• Energy production

• DNA replication

• Host cell recognition and binding

• Protein synthesis

Answer explanation

Attachment proteins in viruses are crucial for host cell recognition and binding, allowing the virus to attach to and enter the host cell. This is essential for the virus to initiate infection.