Download Chapter 19 Bacteria are prokaryotes- unicellular organisms without

Chapter 19
Bacteria are prokaryotes- unicellular organisms without a nucleus. They make up 2 of the 3 kingdoms- K. Eubacteria and
K. Archaebacteria.
Because prokaryotes are so small (1-5 micrometers vs. 10-100 micrometers in eukaryotes), they are identified by shape,
cell wall composition, and movement.
-Shape: There are 3 main shapes
1. Rod Shaped= Bacilli
2. Spherical= Cocci
3. Spiral= Spirilla
-Cell Wall: Two main types- Those with thick peptidogylcan wall and those with a thin peptidogylcan wall. You can tell
them apart using Gram staining- a dye that stains the peptidogylcan dark violet. Gram positive have the thick wall and are
violet, Gram negative have the thin wall and are pink.
-Movement: Some do not move at all, some have flagella (whip like tail), some snake forward, others glide on a slimy
material they secrete.
There are two main ways bacteria obtain energy:
1. Heterotrophs- Get energy from other organisms
a) Chemoheterotrophs: Must take in organic molecules for energy and a carbon source. Humans are also
chemoheterotrophs.
b) Photoheterotrophs: Photosynthetic, but must also take in organic molecules for a carbon source.
2. Autotrophs- Get energy from sunlight or chemical reactions.
a) Photoautotrophs: Photosynthetic
b) Chemoautotrophs: Do not require light- get energy from chemical reactions. (Some live in deep ocean vents, getting
energy from hydrogen sulfide gas.)
How do bacteria release energy (respire)? There are 3 ways:
1. Obligate aerobes- Must have oxygen
2. Obligate anaerobes- Can not live in the presence of oxygen
3. Facultative anaerobes- Can survive with or without oxygen
Bacteria can grow and divide very quickly! Some as often as every 20 minutes. At that rate, a single bacterium within 48
hours could become a bacterial mass about 4000 times that of the Earth! This does not happen, because availability of
food and production of waste products keeps growth in check.
There are 3 types of bacterial reproduction.
1. Binary fission: Most do this. Grows, replicates DNA, divides in half.
2. Conjugation: A hollow bridge forms between to bacteria, and they exchange genetic information.
3. Spores: When conditions are harsh, a spore containing DNA forms and grows when conditions are favorable again.
Viruses are the smallest microbes. The are composed of a DNA or RNA core surrounded by a protein coat called a
capsid. The capsid have receptors that allow it to attach to the cell surface and trick it into letting it in. Once inside, the cell
then replicates the viral genetic information. Viruses are very specific to the types of cells they infect. Those that infect
bacteria are called bacteriophages.
Viruses cause two different types of infections in cells:
-Lytic: The virus enters the cell and replicates itself from mRNA produced by the cell. The viral mRNA then chops up the
cell's DNA causing it to burst and release the virus.
-Lysogenic- The virus causes the cell's DNA to replicate the viral DNA like a copy machine, then the viruses exit the cell.
Disease
-Bacterial: Can be prevented with a vaccine or cured with antibiotics. Ex. Lyme disease, tetanus, strep throat, tooth decay.
-Viral: Can be prevented with a vaccine, but can not be cured with medications. Ex. common cold, flu, AIDS, chicken pox,
measles.
Chapter 20
We can group protists into three main groups: animal like, plant like, and fungus like.
Animal Like Protists- Heterotrophs that are classified based on movement.
-Phylum Zoomastigina: Move with 1 or 2 flagella.
-Phylum Sarcodina: Move with psuedopods- temporary extensions of the cytoplasm. Amoebas are an example
-Phylum Ciliophora: Move with cilia- hundreds of small, beating, hairlike structures.
-Phylum Sporozoa: Do not move. Are parasitic.
Malaria, one of the world's most infectious diseases, is caused by a sporozoan protist carried by female mosquitos.
Plant like Protists: Photosynthetic autotrophs. 7 phyla, classified based on unicellular or multicellular.
Unicellular plant like protists
-Phylum Euglenophyta: have two flagella, but no cell wall.
-Phylum Chrysophyta: have gold colored chloroplasts
-Phylum Bacillariophyta: Diatoms. Produce cell walls rich in silicon- the main ingredient in glass.
-Phylum Pyrrophyta: Dinoflagellates. Half are autotrophs, half heterotrophs. Have flagella and a cell wall.
Multicellular plant like protists= Algaes classified by photosynthetic pigments
-Phylum Rhodophyta: Red Algae. Have phycobilins that make them red and enable them to live in deep water.
-Phylum Pheophyta: Brown Algae (Kelp). Have fucoxanthin brown pigment.
-Phylum Chlorophyta: Green Algae. Have same pigments as plants.
Human Uses for Algae
-Produce much of the Earth's oxygen. About 1/2 of all photosynthesis on earth is by algaes.
-Chemicals in algae used in medicines for many health problems.
-Used as or in food: Nori, ice cream, salad dressing, pudding, pancake syrups, etc..
-Chemicals used to make plastics, waxes, deodorant,and paints.
Fungus Like Protists: Heterotrophs that absorb nutrients from dead or decaying matter. Have centrioles (true fungus don't)
and lack chitin in cell wall (true fungus have it).
-Slime Molds: Found in damp areas rich in organic matter (forest floor, compost).
-Water Molds: Found on dead/decaying matter in water.
Chapter 21
Fungi are eukaryotic heterotrophs that have a cell wall. All, except yeast, are multicellular. They can reproduce asexually
or sexually (via spores).
There are 4 main groups of Fungi, classified according to structure and reproduction.
-Phylum Zygomycota: Common molds (like on cheese/bread).
-Phylum Ascomycota: Sac fungi. Yeasts are in this phylum. Dry yeast granules have spores which are activated when
moist.
-Phylum Basidiomycota: Club fungi. Mushrooms. Spores found on the underside of the gills.
-Phylum Deuteromycota: Sexual phase has not been observed to allow for classification. Penicillium sp. which looks like a
mold and produces the antibiotic penicillin is in this group.
In humans, parasitic fungi can cause diseases such as athlete's foot (A deuteromycete), which is easily spread.