what are prokaryotes? - mrs. parker's biology...
TRANSCRIPT
What are prokaryotes?
ALWAYS unicellular organisms
NO nucleus
NO membrane-bound organelles
Two types: Archaea and Bacteria
Prokaryotic Size
Very tiny compared to eukaryotic cells
Comparing Eubacteria and Archaebacteria
EUBACTERIA
o Thick peptidoglycan cell walls
• Some have two cell walls
o Some are photosynthetic (cyanobacteria)
ARCHAEBACTERIA
o No peptidoglycan in cell walls
o Different lipids in cell membranes
o Different ribosomal proteins and RNA
Bacterial Shapes
Spirrilum – spiral-shaped
– Used to classify bacteria
Prokaryotic Structures Cell membrane
o Function – controls what enters and leaves the cell
o Phospholipid bilayer embedded with proteins
o Around the cell between the cytoplasm and the cell wall
o Found in ALL bacteria
Prokaryotic Structures
Cytoplasm
o Function – the fluid in the cell that supports the cell structures
o Mostly water with dissolved particles, proteins, and cell structures
o Inside the cell membrane (all over the cell)
o Found in ALL bacteria
Prokaryotic Structures DNA
o Function – stores the genetic material
o Nucleotides form the double helix that is arranged into a circular chromosome
o Floats in the cytoplasm in the center of the cell
o Found in ALL bacteria
Prokaryotic Structures
Ribosomes
o Function – site of protein synthesis
• (AKA – where proteins are made)
o Made of rRNA and proteins
o Floating in the cytoplasm
o Found in ALL bacteria
Prokaryotic Structures Cell Wall
o Function – provides structure, support, and protection
o Made of peptidoglycan (proteins and sugars)
o Around the outside of the cell membrane
o Found in ALL bacteria
Prokaryotic Structures Cell Wall
o Used to classify bacteria
• Gram –positive
• have lots of peptidoglycan
• appear dark purple when stained
• Gram-negative• have an outer lipid layer
• appear pink when stained
• Some antibiotics work by attacking the cell wall
• Doctors need to know which type of bactiera in order to prescribe the correct antibiotic.
Prokaryotic Structures
Capsule –
o Functions
• Keeps the cell from drying out
• Helps the bacteria attach to surfaces in its environment
• Protects the cell from being broken down by white blood cells and the effects of antibiotics
o A layer of sticky carbohydrates
o Surrounds the cell wall
o Found in SOME bacteria
Prokaryotic Structures
Pili –
o Function – helps the cell stick to surfaces or be a bridge between cells to swap plasmids
o Small hair-like structures made of protein
o Found on the outer surface of SOME bacteria
Prokaryotic Structures
Flagella (flagellum – only one)
o Function – to move the cell through its environment toward light, food, or more oxygen
o Made of proteins
o Located outside of the cell
o Found in SOME bacteria
o Other bacteria are stationary or move by sliding over secreted slime (YUM!)
Prokaryotic Structures
Plasmid
o Function – stores EXTRA genetic information
o Nucleotides form the double helix that is arranged into a small circular chromosome
o Floats in the cytoplasm
o Found in MOST bacteria
Label the Bacteria
Metabolism in Prokaryotes How do they get their energy?
Bacteria differ in the way they obtain energy and nutrients
Autotroph – an organism that produces its own nutrients
o Photoautotroph – use energy from the sun (cyanobacteria)
o Chemoautotroph – use energy from inorganic compounds (many archaebacteria)
Metabolism in Prokaryotes Heterotroph – an organism that must eat other
organisms to obtain nutrients and energy
o Most bacteria are heterotrophs that break down organic matter (decaying organisms or organic waste)
o Some bacteria are parasites that cause diseases and infections
Metabolism in Prokaryotes
Aerobes – Bacteria that require oxygen
Anaerobes – Bacteria that do not need oxygen (use fermentation to obtain energy from carbohydrates)
Facultative anaerobes – Can use oxygen but can survive without it
How do the bacteria grow in the nutrient broth?
Aerobe Anaerobe Facultative
Anaerobe
O2 O2 O2
Nutrient Broth
Contains
nutrients for the
bacteria
Reproduction in Prokaryotes
Binary Fission
o What happens?
1) Chromosome is copied
2) Cell elongates
3) A new piece of cell wall and cell membrane forms and separates the cells
o Asexual reproduction – produces two genetically identical daughter cells
o Can happen every 20 minutes in ideal conditions
• 1 to 1,000,000,000 in 10 hours
Asexual Reproduction
Reproduction in Prokaryotes
Conjugation
o Happens when two bacteria attach to each other using pili and swap genetic information
o Creates new gene combinations and variation among bacteria
Bacterial Survival Skills
How do bacteria survive when conditions get rough?
o Lack of water
o Extreme temperature change
o Lack of nutrients
o Exposure to radiation (UV light)
Bacterial Survival Skills Endospore – a dormant cell that contains the cell’s DNA
and a small amount of cytoplasm and can survive for long periods of time in harsh environmental conditions
o Produced by SOME bacteria like anthrax, botulism, tetanus
o When conditions are favorable again, a new bacterium germinates from the endospore
Bacterial Survival Skills
Rapid reproduction
o Bacteria reproduce rapidly and can quickly regrow a population
Mutations
o Random errors in DNA that leads to new forms of genes and sometimes new traits that help some bacteria survive and reproduce better than others
Benefits of Bacteria Environment
o Autotrophs produce oxygen
o Convert nitrogen into a usable form for all other organisms (nitrogen fixation)
o Help decompose dead organisms and return nutrients to the environment
Benefits of BacteriaMedicine
o Genetically engineered bacteria produce many medicines in bulk to reduce cost
• Example: Insulin
o Some antibiotics were originally made by bacteria
• Examples: Streptomycin, bacitracin, tetracycline, vancomycin
Benefits of Bacteria
Industry
o Help make/produce foods
• Yogurt, buttermilk, cheese, chocolate, pickles, soy sauce, & sourdough bread
o Produce vitamins (B12 and riboflavin)
o Produce chemicals (acetone, vinegar)
o Used in mining
o Clean up oil spills
o Used in sewage treatment plants
Bacteria and Research
Important in genetic research
o Provide information about DNA
• It’s DNA is simple (one ring)
• Reproduce quickly with short generations so species can evolve quickly
o Less ethical issues
Bacteria and You
Normal Flora – the bacteria that live in and on our bodies
o Most are harmless
o Compete with harmful bacteria and help prevent sickness
o E. coli lives in your intestinal tract and makes vitamin K that we need
Disease-Causing Bacteria
Only a small percentage of bacteria cause diseases.
Pathogen – an infectious agent that causes disease or illness to the host
Disease-Causing Bacteria Your immune system is
always working to identify and destroy foreign invaders.
o Antibodies identify the invaders.
• You only have antibodies to diseases that have been in your body before.
o White blood cells bring invaders into the cell by endocytosis and destroy them using their lysosomes.
Disease-Causing Bacteria
How do bacteria cause diseases?
o Reproduce quickly in one part of the body and spread faster than the immune system can destroy them
o Secrete toxins that harm/kill the host’s cells so that the bacteria can use the nutrients
• Botulism bacteria paralyze cells in the nervous system
• Bacteria that cause cavities use sugars in the mouth for energy and secrete acids that erode teeth
How do contagious diseases spread? Bodily fluids
Bites
Through the air
Contaminated food/water
Found on everyday objects
Antibiotics Antibiotic – a drug that is used to kill bacteria or slow
their growth
o Only treat bacterial infections!
o Antibiotics do not treat viruses!
o Some work by preventing cell walls from being built which makes the cell easier to destroy.
o Some work by blocking ribosomes so that proteins cannot be made.
o Some work by breaking the DNA strand during replication and preventing its repair.
Penicillin – The First Antibiotic
Antibiotic produced by the fungus Penicillium
Discovered by Alexander Fleming in 1928
Antibiotic Resistance
Some bacteria have traits that make them resistant to an antibiotic
o These bacteria survive and reproduce better than others when antibiotics are present.
o Over time, the population of bacteria evolves to be resistant to antibiotics
Resistance types
Why are bacteria more resistant today?
Overuse
Patients do not finish prescriptions
Resistance
video
How do bacteria become resistant to antibiotics?
Resistance Scale(Least Most)
2 3 4 51
1 Original bacterial population with
genetic variation
15
54
4
3
33
2
2
2
2
11
11
2 Antibiotic Treatment
(Less resistant bacteria die)
15
54
4
3
33
2
2
2
2
11
11
3 The more resistant bacteria survive,
swap plasmids, and reproduce
5
54
4
4The next generation is a more
resistant population
5
5
4
4
5
54
4
5
5
4
4
Vaccines
Vaccine – a harmless form of a pathogen used to stimulate the immune system to recognize and destroy the pathogen
o Can be used for bacterial and viral pathogens
Vaccines Why do you get sick after
some vaccinations?
o Your body is reacting to the harmless pathogen as it would to a harmful pathogen.
o The symptoms (fever, fatigue, …) are your body’s response to pathogens.
Viruses Virus – an infectious particle that consists of a nucleic
acid enclosed in a protein shell (capsid).
Viruses
ALL viruses have:
o Nucleic acid – DNA or RNA
o Capsid protein coat
Viruses Some have an envelope
o A lipid membrane that surrounds the capsid
o Forms from the cell membrane or nuclear membrane of the host cell.
o Envelope proteins on the surface of the virus are picked up from the host cell as the virus leaves
• Helps the virus avoid detection and get into a new host cell
Types of Viruses
Bacteriophage Human Virus
(infects bacteria) (HIV)
Lytic Cycle
Infection Replication Cell Destruction
1. The virus injects its DNA/RNA into the host cell.
2. The viral DNA takes over the cell and uses the cell’s materials to make more virus parts.
3. Once the cell has produced enough parts, the new viruses burst out of the cell causing the host cell to die.
4. The new viruses go and infect more cells and the process begins again.
Lysogenic Cycle1. The virus injects the DNA/RNA into
the cell.
2. The viral DNA is added to the cell’s DNA.
3. The cell copies the viral DNA every time the cell divides.
4. Virus parts are not made.
5. The cell lives, but produces infected daughter cells.
❖Environmental triggers cause the virus to switch to the lytic cycle.
Viral Replication
So, are viruses living?
Do they have all the characteristics of life?
• Heredity
• Responsiveness
• Homeostasis
• Made of Cells
• Growth
• Metabolism
• Reproduction
×
×
×
×
×
Viral Diseases Can affect bacteria, plants, and animals, but are very specific
o A bacteriophage can only affect bacteria.
Because viruses replicate using the host’s cells, it is difficult to make drugs that will not harm the host.
Viral Diseases Named by the disease it
causes
o Not living cannot be named and classified like living organisms
Once our bodies have the virus under control, its DNA remains in the cells replicating by the lysogenic cycle
o You never get rid of a virus.