2.1-A Microscopic Look at Life’s Organization SB1 3U- Ferrari

All living things are composed of cells… All species of living organisms ( ie. unicellular or multicellular) are comprised of cells All living things can be studied using a microscope. Scientists also investigate and classify viruses, even though they are not considered alive. Viruses differ from prokaryotic and eukaryotic cells in that: 1) they depend on the internal physiology of cells 2) they are not cellular and do not have cytoplasm and other membrance bound organelles

What is a Virus? Virus- A structure that contains strands of DNA or RNA surrounded by a protective protein coat. It can only live inside cells. -They are not considered to be living

Classifying Viruses Scientists classify viruses according to the following criteria: Size and shape of the capsid (protein coat surrounding genetic material) Shape and structure of the virus Type of diseases it causes Type of genetic material (RNA or DNA) Method of reproduction

Reproduction in Viruses Viruses undergo replication inside a HOST cell. They will undergo replication through either 2 cycles: 1) Lytic Cycle 2) Lysogenic Cycle Lytic Cycle Virus Replication Lysogenic cycle

Lytic Cycle A- attachment E- entry R-replication A-assembly R- release

Lysogenic Cycle Here the virus enters a host cell and inserts its DNA ( becomes a provirus) It will then continue on into the lytic cycle.

Viruses and Disease Lytic Viruses Chapter 2: Diversity: From Simple to Complex Viruses and Disease Lytic Viruses In multicellular species, lytic viruses burst from host cells and infect neighbouring cells. Host organisms that are already damaged are affected more rapidly. Lysogenic Viruses Lysogenic viruses may not cause any immediate effects on the host organism. These viruses can lay dormant for a long period of time. Example: HIV (human immunodeficiency virus)

Prions: Non- viral Disease Causing Agents Prion- an infectious particle causing damage to nerve cells in the brain but is not a virus or bacteria Discovered in 1980s They lack DNA or RNA; they convert from their normal form to the harmful form causing severe deadly brain diseases. Ie. Creutzfeldt- Jacob disease ( CJD) or Variant Creutzfeldt- Jacob disease ( vCJD)

Prions are only known non-genetic disease agent. They become harmful when they change molecular shape. They remain infectious even after exposure to radiation

Homework Read and make note 2.1- pgs 52-56 Complete the following: