1 - Cell biology Flashcards
Prokaryotic Cells
- developed 3.5 billion years ago.
- do not have a membrane bound nucleus
- most abundant type on earth today
- simple in structure but biochemically diverse
- Eukaryotic cells developed from prokaryotic cells around 2 billion years ago (maybe earlier) and have a membrane bound nucleus
2 domains of prokaryotes
Bacteria + Archaea
• Archaea often live in very extreme environments
• Bacteria have enormous medical and economic importance.
Nucleoid region
contains circular DNA, no nuclear membrane
What do prokaryotes have instead of a nucleus ?
A nucleoid region which containing circular DNA and also have loops of DNA named plasmids
What are the main 3 shapes and their classified names?
Spherical - cocci
Rod shaped - bacilli
Helical - Spirochetes
What are flagella and what are they composed of?
Projections which aid the movement of the bacteria, made of the protein flagellin.
What are pili and what are they composed of?
Projections which help bacteria stick to their substrate, made of the protein pilin.
What is the capsule secreted by bacteria made up of?
polysaccharides
Do prokaryotes have a cell wall or a cell membrane?
They have a cell membrane known as the plasma membrane or the cytoplasmic membrane.
They also have a cell wall, usually composed of peptidoglycan or murein.
What is the function of the prokaryote cell wall in bacteria?
The cell wall protects the bacterial cell from mechanical and osmotic shocks
How are bacteria classified based on their cell wall? (e.g. what are the 2 types and their cell wall structure?)
Bacteria can be Gram positive or Gram-negative.
Gram-positive bacteria have a thick 40nm layer of peptidoglycan in their cell wall.
Gram-negative have a thin cell wall with a much more complex structure
Which type of bacteria are more dangerous to humans , gram positive or gram negative?
Gram negative - they are also harder to kill
How is bacteria useful in biotechnology? Use examples
Bacteria can be used to produce large quantities of proteins relatively cheaply.
For example, insulin for diabetic patients is now produced using bacteria instead of taking it from dead animals.
What modes of nutrition exist amongst prokaryotes?
photoautotrophs
chemoautotrophs
photoheterotrophs
chemoheterotrophs
Photoautotrophs
Photosynthetic organisms which use light to synthesize organic compounds from Carbon Dioxide
Chemoautotrophs
Use carbon dioxide as a carbon source and obtain their energy by oxidizing inorganic substances
e.g. from hydrogen sulphide, ferrous ions e.g. Sulpobolus oxidise sulphur.
This mode of nutrition is unique to certain prokaryotes
Photoheterotrophs
Use light to generate ATP but must obtain their carbon in an organic form. This type of nutrition is unique to certain prokaryotes
Chemoheterotrophs
Use organic molecules to supply both carbon and energy
Why are viruses not considered to be alive?
They cannot self repair and do not have an energy transduction system.
Why were viruses only discovered relatively recently?
They are only visible with an electron microscope
4 groups viruses can be classified into
Filamentous
Spheroid
Tailed spheroid
Enveloped
Filamentous viruses
The nucleic acid is arranged in a helix , with the protein sub-units surrounding and stabilizing it. An example is Tobacco mosaic virus
Spheroid viruses
The nucleic acid is condensed inside a protein envelope which is usually
organized into a multisided geometric shape.
An example are adenovirus different types cause illness ranging from Gastroenteritis to keratoconjunctivitis.
Tailed spheroid virus
This is basically a spheroid virus with a tail. An example is the lambda phage
Enveloped viruses
Have lipid envelopes includes the influenza and coronaviruses viruses
Examples of pathogenic gram negative bacteria
- Chlamydia trachomatis
- Vibrio cholerae (cholera)
- Yersinia pestis (plague)
Examples of pathogenic gram positive bacteria
- Clostridium botulinum (botulism)
- Streptococcus pneumoniae (pneumonia)
How are flagellum powered?
A motor in the plasma membrane which powers a hook which causes movement.
Which domains of life has a circular chromosome present?
Bacteria and archaea
Which domains of life has histones present?
Archaea and Eukarya
What is each domain of life’s response to antibiotics, streptomycin and chloramphenicol?
bacteria = growth inhibited
Archaea and Eukarya = growth not inhibited
Are introns present or absent in which domains of life?
Absent = bacteria
Present in some genes = archaea
Present = Eukarya
Which initiator amino acid does each domain of life have?
Methionine= archaea and eukarya Formyl-methionine = bacteria
Which hydrocarbons are present in which domains of life?
Unbranched = bacteria and eukarya
Some branched = archaea
Which domain of life only have one kind of RNA polymerase?
Bacteria
