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18 Cards in this Set
- Front
- Back
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2 features common to all viruses |
-surrounded by a protein coat -contain nucleic acid |
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Bacteriophages |
Viruses of bacteria which contain DNA |
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Bacteriophage lifecycle |
-phage attaches to bacteria using tail fibres -phage uses contractile sheath to inject viral DNA into host bacteria -viral DNA used to synthesis viral protein coats using bacterial ribosomes. Viral DNA replicates many times -virus assembly = DNA enters capsid and proteins assemble to form many new bacteriophages - viruses emerge from bacteria by breaking open bacterial membrane- destroying host |
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Retroviruses |
Contains RNA and contains enzyme reverse transcriptase e.g. HIV |
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Retroviruses |
Contains RNA and contains enzyme reverse transcriptase e.g. HIV |
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HIV |
Invades T lymphocyte cells called helper T cells |
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How HIV works = |
- virus enters T cell and reverse transcriptase enters the nucleus of the helper T cell -the reverse transcriptase catalysis synthesis of DNA from RNA -DNA is used to synthesis new protein coats and viral coats are assembled -the new viruses rupture out of the helper cell destroying it -progressively more T cells are destroyed so immune system becomes compromised and medical condition aids develops |
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What is same in HIV and bacteriophage |
-both contain nucleic acid core -contain protein capoid -non cellular Extremely small |
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Differences in bacteriophage and HIV |
-bacteriophage contain DNA as nucleic acid core. HIV contains RNA as nucleic acid core -HIV has a bilayer bacteriophage doesn’t have bilayer - bacteriophage host cell is bacteria HIV host cell is T helper cell Bacteriophage contains no surface glycoprotein HIV does Bacteriophage has tail fibres attached to base plate for attaching to a host cell HIV doesn’t |
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Differences in bacteriophage and HIV |
-bacteriophage contain DNA as nucleic acid core. HIV contains RNA as nucleic acid core -HIV has a bilayer bacteriophage doesn’t have bilayer - bacteriophage host cell is bacteria HIV host cell is T helper cell Bacteriophage contains no surface glycoprotein HIV does Bacteriophage has tail fibres attached to base plate for attaching to a host cell HIV doesn’t |
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Why aren’t viruses true cells? |
They have no cytoplasm or associated organelles as they only become active within a living host cell |
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Eukaryotic cells |
Large cells which contain nucleus and membrane bound organelles Plant cell= cellulose cell wall Fungi = chitin cell wall No cell wall on animals Spindle fibres and other microtubules present |
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Prokaryotic cells |
Small cells which don’t contain nucleus or other membrane bound organelles DNA is free in cytoplasm. Cell wall is made of glycoprotein and plasmids are present. E.g bacteria |
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Nucleus |
Largest organelle within a cell Surrounded by a double membrane called the envelope containing pores which enables molecules to enter and leave the nucleus. Allows nucleus to communicate with cytoplasm Contains Chromatin which is how chromosomes are diffusely organised therefore contains cells genetic information Contains nucelolus which synthesis rRNA which makes ribosomes |
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Nucleus |
Largest organelle within a cell Surrounded by a double membrane called the envelope containing pores which enables molecules to enter and leave the nucleus. Allows nucleus to communicate with cytoplasm Contains Chromatin which is how chromosomes are diffusely organised therefore contains cells genetic information Contains nucelolus which synthesis rRNA which makes ribosomes |
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Chromatin and the two types |
This is the form that DNA is seen in a cell that is not dividing because the DNA IS spread out and can’t be seen as chromosomes Heterochromatin = tightly packed, controls gene expression and stains darkly Euchromatin= lightly packed, rich in genes( which code for protein synthesis) light coloured band |
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Role of nucleus in protein synthesis |
-nucleus produces rRNA which makes up ribosomes -the chromosomes within the nucleus contains genes that have specific nucleotide sequences that determine the primary structure -the nucleotide sequence in a gene is used to create messenger RNA molecule that carries a copy of the gene code an scan be carried out of nucleus via nuclear pores |
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Rough ER |
Series of flattened sacs enclosed by a membrane with ribosomes on the surface Folds and processes proteins made on the ribosomes Facilitates transport of RNA from nucleus to ribosomes |
