AQA A Level Biology: Structure of Prokaryotic Cells and viruses Flashcards
What is a prokaryotic cell?
A simple, unicellular organism that lacks a membrane-bound nucleus and organelles.
What is the genetic material in prokaryotic cells?
A single circular DNA molecule found in the nucleoid region, not enclosed by a membrane.
What are plasmids?
Small, circular DNA molecules that replicate independently and often carry genes for antibiotic resistance.
What is the function of the cell wall in prokaryotic cells?
Provides strength and support; made of murein (peptidoglycan).
What is the function of the plasma (cell surface) membrane?
Controls the movement of substances in and out of the cell through selective permeability.
What are ribosomes like in prokaryotic cells?
Smaller (70S) ribosomes that carry out protein synthesis.
What is the function of the flagellum?
Provides motility by rotating to move the cell.
What is the capsule and its function?
A slimy outer layer that protects the cell from desiccation, phagocytosis, and helps in adhesion to surfaces.
What are villi and their function?
Hair-like structures that allow attachment to surfaces and facilitate transfer of genetic material between cells.
How do prokaryotic cells reproduce?
By binary fission, a type of asexual reproduction where the DNA replicates and the cell splits into two identical cells.
What are viruses?
Acellular particles that can only reproduce inside a host cell.
What is the structure of a virus?
- Genetic material: DNA or RNA.
- Capsid: Protein coat surrounding genetic material.
- Attachment proteins: Allow virus to bind to host cells.
How do viruses replicate?
- Attach to host cell using attachment proteins.
- Inject genetic material.
- Host cell machinery replicates viral components.
- New viruses assemble.
- Host cell bursts, releasing viruses.
What is a bacteriophage?
A type of virus that infects bacteria.
Why are antibiotics ineffective against viruses?
Antibiotics target prokaryotic structures, which viruses lack, as they are acellular and rely on host cells for replication.
What is the difference between prokaryotic and eukaryotic cells?
- Prokaryotic cells lack a nucleus and membrane-bound organelles.
- Eukaryotic cells have a nucleus and organelles.
What is the size of prokaryotic cells?
Typically 0.1–5 µm in diameter, much smaller than eukaryotic cells.
What are mesosomes?
Infoldings of the plasma membrane in prokaryotic cells, possibly involved in cell division and respiration.
