2.1 Structure of prokaryotic cells and of viruses Flashcards
What is a prokaryotic cell?
- smaller than eukaryotic cells
- do not have a nucleus or a nuclear envelope
What is the structure of a prokaryotic cell? (x11)
- range from 0.1 to 10μm in length
- cell wall (murein)
- cell membrane
- cytoplasm
- 70s ribosomes
- circular DNA
- plasmids
- food granules
- capsule (most)
- flagella (some)
- pili (some)
What is a capsule?
- made of secreted slime
- protects the cell
- helps groups of cells stick together for further protection
- prevents desiccation
- acts as food reserve
- provides mechanical protection against phagocytosis and external chemicals
What is circular DNA?
- no nucleus
- genetic material is in the form of a circular strand found in the nuclear region of the cell
- possesses the information for the replication of the cell
What are plasmids?
- smaller circular pieces of DNA
- genes that may aid in survival of the cell in adverse conditions
- can pass plasmids between cells
What are flagella?
- some prokaryotic species have flagella (one or more flagellum)
- used for locomotion
What are pili?
- some prokaryotic species have pili (one or more pilus)
- used to adhere to other cells
What are viruses?
- acellular
- non living particles
What is the structure of a virus?
- smaller than bacteria (20-300nm)
- contains nucleic acids such as DNA and RNA but can only multiply inside host cells
- have a protein coat called a capsid
- sometimes have a lipid envelope (containing attachment proteins)
- linear genetic material (DNA or RNA) and viral enzymes
What is the function of stroma?
the fluid of the stroma possesses all the enzymes needed to make sugars in the second stage of photosynthesis.
What is the function of grana?
the granal membranes provide a large surface area for the attachment of chlorophyll, electron carriers and enzymes that carry out the first stage of photosynthesis. These chemicals are attached to the membrane in a highly ordered fashion.
What is the structure of an enveloped virus?
• simple virus surrounded by matrix protein
• matrix protein surrounded by envelope derived from cell membrane of host cell
• attachment proteins on surface
What is the role of the capsid on viral particles?
• protect nucleic acid from degradation by restriction endonucleases
• surface sites enable viral particle to bind to and enter host cells or inject their genetic material
What is the role of attachment proteins on viral particles?
enable viral particles to bind to complementary sites on host cell: entry via endosymbiosis
