Unit 4- Bacteria and virus Flashcards
1
Q
Name the components and functions of a bacteria cell.
3.4.6.8
A
- Cell wall- Prevents swelling and bursting. Also maintains the shape and provides protection
- Cell surface membrane- Site of respiratory enzymes
- Mesosomes- Unknown
- Capsule (slime layer)- Protects the bacteria from phagocytosis and covers cell markers. Helps to survive dry conditions
- Sex pili- Used for bacterial reproduction. Also a point of entry
- Flagella- Movement
- Ribosomes- Produce proteins
- Genetic material- Circular DNA in cytoplasm, also present as plasmids
2
Q
What are the components and functions of a virus cell?
3.4.6.8
A
- Genetic material- RNA or DNA. Injects into host cell
- Protein coat (capsid)- made of capsomeres
- Lipid envelope- Covers the genetic material and coat.
- Proteins- Used to aid the cell e.g. reverse transcriptase
- Receptors- Used to bind to host cells
3
Q
How do bacteria reproduce?
3.4.6.8
A
- Through binary fission
- Transformation- Short piece of DNA released by a donor and taken by a recipient where it replaces a similar piece of DNA.
- Transduction- Small amount of DNA transferred between bacteria by a bacteriophage.
- Conjugation- Genetic information transferred by pili
4
Q
How do virus reproduce?
3.4.6.8
A
- Injects genome into host bacterial cell
- Viral DNA forms a plasmid within the bacterium
- Can go along the lytic or lysogenic pathway
- Lysogenic- Non virulent at first. Injects DNA into host DNA therefore when host divides, virus DNA also divides. Inserted DNA is a provirus.
- Lytic- Replicates independtly of the host DNA. Mature viruses are made and burst out of cell and infect other cells
5
Q
What is a retrovirus and explain its life cycle?
3.4.6.8
A
- Have RNA as a genetic material
- Translated into DNA through reverse transcriptase
- Viral DNA passes into nucleus of the cell
- Host transcriptase produces viral mRNA and new RNA
- Viral material synthesised and leave the cell by exoytosis
- Host cell is a factory for viruses
6
Q
What are the barriers to infection?
3.4.6.10
A
- Stomach acid- Killed by Hydrochloric acid in the stomach. Can enter through contaminated food and drinks
- Skin- Physical barrier made of the protein keratin. Impenetrable apart from an open wound. Sebum also produced which prevents the growth of microorganisms
- Gut and skin flora- Naturally covered in harmless microorgaisms which compete with pathogens for space and nutrients.
- Lysozyme- Mucosal surfaces produce secretions that contain lysozyme. Damages the cell walls causing the pathogen to burst
- Vomiting- Discharged out of the body removing microorganisms.
7
Q
What are the non-specific reactions to infections?
3.4.6.12
A
- Inflammation
- Lysozyme action- Destorys bacterial cell walls causing them to burst
- Interferons
- Phagocytosis
8
Q
Explain inflammation
3.4.6.12
A
- Site of infection becomes red,hot,swollen and painful
- Mast cells become damaged
- Histamines are released
- Causes vasodilation around the site of infection increasing blood flow
- Increased blood flow causes local heating which decreases the effectiveness of pathogens
- Permeability of blood vessels increases
- Causes an increase in white blood cells to site of infection
WBC destroys the pathogens
9
Q
Explain interferons
3.4.6.12
A
- Only affects viruses
- Interferons prevent viruses taking over healthy cells
- Inhibits the production of viral proteins
- Also activates the specific responses to kill infected cells and other responses occur
10
Q
Explain phagocytosis
3.4.6.12
A
- Carried out by phagocytosis which are white blood cells
- Found in the blood and tissues,and are first to respond to pathogens
- Recognises non self antigens on the pathogens
- Engulfs the pathogen
- Pathogen is contained in a phagocytic vacuole
- Lysosome fuses with the vacuole and lysozyme is released to break downn the pathogen
- Phagocytes presents the pathogens antigen on the surface of the phagocyte for the specific response
11
Q
A
