What to Expect: These notes focus on –Cell theory –Prokaryotes
Cell theory 1.All living things are made of cells 2.Cell can only come from other cells 3.All functions of a living thing are carried out in cells Reminder: the functions of living things are: respiration, metabolism, growth, adaptations to the environment, reproduction, homeostasis and interdependence
On your worksheet 1.State the 3 points of cell theory. 1.List the 7 characteristics of life
There are two main groups of cells, prokaryotic and eukaryotic cells. Similarities: all are alive, all have a cell membrane, all have DNA Differences: appearance, structure, reproduction, and metabolism. –biggest differences are between cells of different kingdoms.
Prokaryotes are bacteria Prokaryotes are simple organisms VS Diagrams courtesy - http://www.cod.edu/people/faculty/fancher/ProkEuk.htm
According to current scientific thought; Prokaryotes were formed 2 billion years before eukaryotes (or about 3.5 billion years ago)
On your worksheet According to current scientific thought, about how old are prokaryotes?
Prokaryotes from the Greek meaning “before nuclei”
Why “before nuclei?” Prokaryotic cells have no nucleus. Prokaryote’s DNA is circular (it has no ends). –Small circlets of DNA are called Plamids. Prokaryotic DNA is “naked” – it has no histones associated with it and does NOT form chromosomes
On your worksheet What does prokaryote mean? Why is the term prokaryote used to describe the cells we are talking about?
All Prokaryotes are in the monera kingdom domains Bacteria and Archaea –bacteria–Cyanobacteria also known as blue- green algae
On your worksheet What kingdom to do all prokaryotes belong to?
Prokaryote Characteristics 1.Very small size. 2.Lack membrane-bound organelles inside the cell 3.have few internal structures that are distinguishable under a microscope. 4.genetic information is in a circular loop called a plasmid 5.Strong cell walls: resistant to environmental changes
1.Size Bacterial cells are very small, roughly the size of an animal mitochondrion –about 1-2µm in diameter and 10 µm long –µm = one millionth of a meter, or equivalently one thousandth of a millimeter.
On your worksheet What is the size of an average Prokaryote?
2. Lack membrane-bound organelles inside the cell
3. have few internal structures that are distinguishable under a microscope. http://www.umanitoba.ca/science/biological_sciences/lab3/biolab3_2.html#Examine
4. genetic information is in a circular loop called a plasmid E. coli cell dividing. E. Coli Grows in human intestine; –Has a single, circular chromosome –contains DNA as plasmids Plasmids are extra- chromosomal DNA http://www.bio.mtu.edu/campbell/prokaryo.htm
5. Strong cell walls: resistant to environmental changes
On your worksheet Describe the 5 items used to classify a prokaryote
Shapes Cocci - sphere Bacilli - rods Spirilla – spirals Staph - in clusters Strep - in chains Spiral Rod shaped Spherical Streptococcus sp. Chains of nearly- spherical bacteria. From The Rockefeller University.The Rockefeller University. This spiral shaped bacteria is the causitive agent of syphilis Treponema pallidum
Streptococcus sp. Chains of nearly- spherical bacteria. From The Rockefeller University.The Rockefeller University. Means Sphere-shaped Streptococcus pyogenes
This spiral shaped bacteria is the causitive agent of syphilis Treponema pallidum Means Spiral-shaped
Some bacteria can be identified by how they move –Stationary (don’t move at all) –Flagella (whip like structure) Rotation and tumbling Number of flagella –Monotrichous –Lophotrichous –Amphitrichous –Peritrichous Spiraling –Slime and ooze
Which means, some bacteria simply do not move - - at all, ever.
Some bacteria are propelled (moved) by a whip-like structure called a FLAGELLA –Flagella can be rotated like tiny outboard motors –When flagella rotation is reversed, bacteria tumble about in one place.
–Monotrichous- Having one flagellum at only one pole or end –Lophotrichous- having a tuft of flagella at one end –Amphitrichous- having flagella at both ends –Peritrichous- Having flagella uniformly distributed over the body surface
Like a corkscrew –Kinking different parts of the bacteria body by hardening one side and then the other
Other bacteria secrete a slime layer and ooze over surfaces like slugs. –slime layer is formed by decomposition of the cell wall.
Click picture to watch video on Bacterial Reproduction
Replication Binary fission – one cell splits into two cells, offspring are genetically identical to parent
Bacterial conjugation – a form of sexual reproduction where bacteria exchange genetic information before dividing offspring have new genes (and new traits) Figure 1. Schematic drawing of bacterial conjugation. 1- Donor cell produces pilus; 2- Pilus attaches to recipient cell, brings the two cells together; 3- The mobile plasmid is nicked and a single strand of DNA is then transferred to the recipent cell; 4- Both cells recircularize their plasmids, synthesize second strands, and reproduce pili. Both cells are now viable donors. http://parts.mit.edu/igem07/index.php/Boston_University/Conjugation
Transformation – bacteria incorporate genes from dead bacteria Transduction –viruses insert new genes into bacterial cells. –This method is used in biotechnology to create bacteria that produce valuable products such as insulin
Movement Some can't move, while others have long threadlike flagella. If bacteria doesn’t move, how does it get from person to person? E.Coli flagella
–4 main ways bacteria get energy Chemoheterotrophs Photoheterotrophs Photoautotroph Chemoautotroph –Energy is released through either cellular respiration or fermentation –Oxygen demands vary Obligate aerobe Obligate anaerobe Facultative anaerobe
Heterotrophs get energy by eating other organisms –Chemoheterotrophs Eat other organisms for Energy Eat other organisms for carbon supply –Photoheterotrophs Use sunlight for energy Eat other organisms for carbon supply
At least 95% of life on earth is heterotrophic (including people) staphylococcus aureus Chemoheterotroph –“eat” same foods as humans –Release toxins that cause food poisoning –Antibiotic resistant strains cause breakout pictured here
Jannaschia marine bacteria found in coastal and open ocean surface waters. aerobic anoxygenic phototroph (AAnP), –Gets its energy from light, not from eating other organisms responsible for oceanic photosynthesis in the ocean and the ocean carbon cycle.
Autotrophs make their own energy from inorganic (not-living) molecules –Photoautotroph Uses sunlight (light energy) to convert CO 2 and H 2 O into Carbon compound and oxygen –Chemoautotroph Make organic carbon molecules from CO 2 using energy from chemical reactions involving ammonia, hydrogen sulfide, nitrites or iron
Cyanobacteria –Also called bluegreen algae –Found in fresh water, salt water and on land near sources of light –Photoautotroph Use sunlight to make energy and carbon compounds
Chemoautotrophs get energy and carbon from chemical reactions Some live near ocean vents like the one pictured
Once bacteria have “eaten” they need to break down their “food” to make energy The process of breaking down organic compounds into ATP (energy cells can use) is called cellular respiration Same 1 st step to begin with, but the lack or presence of oxygen determines the 2 nd step –Step one – Glycolisis –Step two – Fermentation or Kreb Cycle
To oversimplify the first step –called glycolysis Doesn’t require Oxygen (anaerobic) Takes place in the cytosol (fluid surrounding organelles) of a cell Breaks glucose into pyruvate creating ATP and H in the process
If NO oxygen is present after glycolysis, Fermentation begins –3 types Lactic acid Fermentation –Occurs in muscles »causes muscle cramps due to acidity –Occurs in Bacteria »used to make cheese and yogurt Acetic Acid Fermentation –Occurs in Bacteria »Forms vinegar Alcohol Fermentation –Forms ethyl alcohol and CO2 »Used to make bread, wine and beer
If Oxygen IS present after glycolysis, Acetyl CoA is made and the Kreb cycle begins – we’ll save the chemical details of this process for another class, but, basically it produces a whole lot of ATP for the cell to use
SOME BACTERIA REQUIRE OXYGEN, SOME DON’T –OBLIGATE AEROBES –OBLIGATE ANAEROBES –FACULTATIVE ANAEROBES
Obligate aerobes NEED oxygen to live –OBLIGATE means required to –AEROBE means oxygen Release energy through cellular respiration or fermentation Example: myobacterium tuberculosis
Obligate anaerobes DO NOT need oxygen to live –OBLIGATE means required to –ANAEROBE means without oxygen Release energy through cellular respiration or fermentation Example: clostridium botulinum
Facultative anaerobes can survive with or without oxygen –Facultative – means able to function in different ways These bacteria can live just about anywhere Example: E. coli
Functions What does Bacteria do? decomposers, agents of fermentation, and they play an important role in our own digestive system. involved in many nutrient cycles such as the nitrogen cycle, which restores nitrate into the soil for plants.