Define bacteria
- Unicellular organisms - prokaryotic cells (don’t contain membrane enclosed nucleus)
- Grow rapid and are biochemically versatile => tough(accept variety of nutrients), selective (picks best nutrients in environment), adaptable (adapt to environment)
Describe the structure of the bacteria cell wall
All bacteria (except Molicutes) have cell wall - rigid(structural strength), mesh-like biopolymer made of sugars and aminoacids, cell wall covers cell membrane that hold internal contents of the cell, cell membrane important in determining which chemical can be transferred between cell and environment.
What are the two classifications of bacteria based on the cell wall?
· Bacteria classified in two types based on cell wall:
- Gram-positive = very thick wall, bacteria retains purple colour when stained with dye crystal violet
- Gram-negative = double cell walls (inside thin peptidoglycan wall, outer membrane of carbohydrates proteins and lipids), don’t retain purple colour when stained with crystal violet
What are the typical main shapes of bacteria?
- Spherical
- Rod-like
- Spiral
How do bacteria survive adverse environmental conditions?
· Bacteria form endospores to survive adverse environmental conditions
- Vegetative form - normal biological active cell state => bacteria encounters adverse conditions in vegetative state, it forms a spore
What are the two major spore forming bacteria?
Bacillus and Clostridium => clostridium - function under anaerobic conditions, vegetative state - die with oxygen presence
· Some bacteria whose vegetative forms are killed at 45 degrees, form spores which survive in boiling water for hours => kill bacteria - temp > 120 degrees
Define bacterial reproduction
Binary fission - formation of 2 identical bacterial cells, single DNA molecule replicates, favourable conditions - happens every 20 mins
Define bacterial recombination
· Gene transfer between bacterial cells
· Conjugation - One bacterium connects itself to another by means of a tube called pilus. Genes are transferred through this tube.
· Transformation - the bacterium binds the DNA available in their environment and transports it across the bacterial cell membrane => The new DNA is then incorporated into the bacterial cell’s DNA.
Transduction - Involves the exchanging of bacterial DNA through bacteriophages => Bacteriophages are viruses that infect bacteria.
Describe the differences between archaea and bacteria
Archaea found in extreme conditions (extremophiles).
Differ biochemically from bacteria - transfer tRNA are different, bacterial ribosome sensitive to chemical inhibiting agents while archaeal ribosomes are not,
bacteria cell walls contain peptidoglycan while archaeal don’t
Describe the structure of a eukaryotic cell
· Eukaryotic cell
- Endoplasmic reticulum - complex membrane system leading from cell membrane to cell
- Ribosomes - biochemical reaction site on surface of endo retic.
- Nucleus - houses chromosome which contains gene
- Mitochondria - catalyse reactions that supply energy to cell
- Golgi complex, liposomes, vacuoles = isolate chemical reactions or chemical compounds from cytoplasm
Define the fungi group.
Kingdom contains large group of eukaryotic organism - yeast, mould, mushroom
Difference between plant cell and fungal cell?
Plant cell wall contain cellulose, fungal cell wall contains chitin
Define yeast. What is the most common industrial yeast?
Eurkaryotic unicellular organisms
Saccharomyces cerevisiae => alcohol, baking etc
Describe yeast reproduction
· Budding
- Asexual reproduction => small offspring grows on side of original cell which separates from parent once mature => doesn’t occur immediately, leading to clump of yeast cells
· Conjugation
Sexual reproduction - 2 haploid cells conjugate by dissolution of adjoining walls = form diploid cell
Describe moulds
· Mycelia - multi-cellular structures which are highly branched systems of filaments called hyphae
- Mycelium very dense - significant o2 and mass transfer resistance => complications in mould cultivation
What are two important classes of moulds?
Aspergillus and Penicillium
