Single celled organisms

Transcription

1 Single celled organisms

2 Single Celled Organisms Some organisms, unlike plants and animals, consist of only one cell. These organisms are said to be unicellular An amoeba is another name given to an organism that consists of only 1 cell.

3 These unicellular organisms are so small that they must be seen with a microscope. Single celled organisms can be classified into 3 main categories: Protists Bacteria Viruses

4 Protists Protists contain a cell membrane, nucleus and various organelles. Some protists contain chloroplasts. These organisms play an important role in the worlds oxygen production. They are also an important part of many aquatic food chains.

5 Some protists cause disease. These bad protists are known as pathogens. Amoebic dysentery and malaria are two diseases caused by such pathogens.

6 Bacteria These are the smallest and simplest forms of life on earth. Bacteria lack most of the organelles that other cells have. They do not have a nucleus or nuclear membrane.

7 Bacterial shapes: 1. Bacilli Rod shaped 2. Spirilla Spiral shaped 3. Cocci Sphere shaped

8 Bacteria contain a single strand of DNA that controls all of their functioning. In addition, they may contain one or more plasmids. Plasmids are circular DNA molecules that contain non-essential genes.

9 Beneficial bacteria: In our digestive system Make yogurt, cosmetics, swiss cheese Recycle organic matter Photosynthesis producing oxygen Food source for other organisms

10 Harmful bacteria: Produce toxins (poisons) that affect cell functioning Examples: E. coli and Salmonella Bacteria that grow on food and cause nausea, cramps, vomiting, diarrhea

11 Bacteria and Disease The best way to prevent bacterial disease is through sanitation. Washing your hands, food, and plates before eating prevents large amounts of bacteria from entering our bodies.

12 Treating Bacterial Disease Antibiotics are used to treat disease. Antibiotics kill or slow the spread of disease.

13 How Antibiotics Work Most pathogens have antigens on their outer surface. Like a key. Specific antibodies are able to attach themselves to these antigens.

14 In some cases the antibody kills the disease. In other cases it slows the spread of it down enough so that other parts of the bodies defense system can kill it.

15 Viruses Are NOT cells (non-living) Smaller than bacteria (3000 could fit across a period at the end of a sentence!) MUST reproduce inside living cells Have 2 parts: Protein cover Genetic material

16

17 To be able to reproduce, a virus needs a host cell. Once inside, viruses hijack the host s DNA and enzymes to reproduce itself. Some modify the genetic info in the DNA When viral particles are produced, they are released from the cell (lysis) Examples: influenza (flu), smallpox, measles, HIV

18 Vaccines Weakened or dead forms of a virus Stimulate immune system to develop and launch a defense If you are later infected by the virus, your body can destroy it quickly Doesn t work for all viruses! Eg: no vaccine for HIV

19 Reproduction

20 Two types: Reproduction of Viruses 1. lytic cycle destroys the host cell very quickly 2. lysogenic cycle a.k.a. slow or latent virus. Can remain in a cell for years before becoming active destroying the cell

21 The Lytic cycle 1. Attachment: virus attaches to the cell using it s spikes and receptor sites on the c.m. 2. Insertion of viral genes into the cell. Viral DNA becomes part of the cells DNA and takes over the cell s activities 3. Manufacture of viral parts 4. Assembly of viruses 5. Lysis: the cell bursts releasing the new viruses

22 1 Adsorption 2 Penetration 3 Early Replication 4 Late Replication 5 Maturation 6 Release

23

24 Examples of lytic viruses common cold bacteriophage (aka phage) influenza Ebola cold sore (herpes I) Genital herpes II

25 The Lysogenic cycle 1. Attachment 2. virus injects genetic material into cell 3. genetic material is inserted into the host cell s DNA. It is now a prophage 4. viral genes remain dormant for a length of time, but are copied with the host cell s DNA when cell division occurs 5. without warning, the cell will switch into the lytic cycle, producing and releasing many viruses 6. In some types, the viral DNA will cause the cell to become a cancer cell! No viruses are produced in this case.

26 Lysogenic Cycle When the cell divides, the prophage becomes part of any new cells! This will produce many new cells which will now produce thousands of new viruses!

27 Herpes Hepatitis HIV Some phages Lysogenic viruses

28

29 Life cycle summary

30 Living qualities of viruses 1. Capsid or protein coat 2. genetic material either DNA or RNA 3. Some have enzymes (proteins) 4. Some have a lipid coat or capsule

31 Non-living qualities of viruses 1. Acellular (Non-cellular) 2. Do not grow 3. Do not make or use energy 4. Do not respond to stimuli 5. Cannot reproduce on their own 6. Can be crystallized

32 Are viruses alive? viruses require cells to reproduce, and are not cellular they don t fit the Cell Theory: all living things are composed of cells No, they are not considered to be alive!