3.6 - 3.8 Prokaryotic cells, viruses and the cell cycle Flashcards
What is the function of a cell wall in bacteria?
- Physical barrier
- Excludes certain substances
- Protects against mechanical damage and osmotic lysis
What is the function of a capsule in bacteria?
- Protects from other cells
- Helps bacteria stick together
What is the function of a cell surface membrane in bacteria?
- Differentially permeable layer which controls the entry and exit of chemicals
What is the function of a circular DNA in bacteria?
- Genetic information for the replication of bacterial cells
What is the function of a cell plasmid in bacteria?
- Possesses genes that may aid the survival of the bacteria in adverse conditions
Describe a virus
- Acellular
- Non-living
- 20 - 300nm
Name the three types of cell division
- Mitosis - Eukaryotic cells, 2 daughter cells
- Meiosis - Eukaryotic cells, 4 daughter cells
- Binary Fission - Prokaryotic cells, 2 daughter cells
Describe the process of binary fission
- Circular DNA replicates and attaches to the cell membrane
- Plasmids replicate
- Cell growth
- DNA separation
- Cytoplasm constricts and a new cell wall is formed
- There are now two genetically identical daughter cells with one copy of the circular DNA and a variable no of copies of the plasmid
What are the stages of the cell cycle? (2 stages, 5 sub-stages)
Interphase:
- G1 phase (cell growth)
- S phase (DNA replication)
- G2 phase (preperation for mitosis)
Cell division:
- Mitosis
- Cytokinesis
What are the 4 stages of mitosis?
- Prophase
- Metaphase
- Anaphase
- Telophase
Describe what happens during interphase
- Cell actively synthesising proteins
- Chromosomes invisible
- DNA replicates
Describe what happens during prophase
- Chromosomes condense and become visible
- Nucleolus disappears
- Nuclear envelope disintegrates
- Centrioles move to poles of the cell
Describe what happens during metaphase
- Chromosomes line up in the centre of the cell
- Spindle fibres form
Describe what happens during anaphase
- Spindle fibres contract
- Centromeres divide into two
- Chromatids pulled towards poles
Describe what happens during telophase
- Chromosomes reach poles and become indistinct
- Spindle disintegrates
- Nuclear envelope reforms
- Nucleolus reforms
Describe what happens during cytokinesis
- Cytoplasm divides to form two distinct cells
Describe the process of viral reproduction
- The viral attachment protein is complementary to specific receptors on the host cell membrane so can attach
- The content of the virus (e.g viral RNA and reverse transcriptase enzyme) are injected into the host cell by endocytosis
- The reverse transcriptase enzyme copies viral RNA to form DNA
- This is transported to the nucleus
- The viral DNA is intergrated with the host cells DNA
- The host cell produces the viral RNA and proteins required for capsid, envelope and enzymes
- All components exit via exocytosis, creating a new viral envelope from the cell membrane of the host cell (‘budding off’)
Why is mitosis necessary?
- Growth
- Repair
- Reproduction (of single celled organisms)
What is cancer?
- A group of 200+ diseases caused by growth disorder of the cells
- Malignant tumour
Describe malignant tumours
- Grow rapidly
- Less compact
- More likely to be life threatening
Describe benign tumours
- Grow more slowly
- More compact
- Less likely to be life threatening
Describe a cancer treatment that focuses on the G1 phase of the cell cycle
Chemotherapy:
- Prevents synthesis of enzymes needed for DNA replication
- Should prevent S phase
Describe a cancer treatment that focuses on the S phase of the cell cycle
Radiation & some drugs:
- Damage DNA
- If severe DNA damage is detected the cell will destroy itself
