3.6 Prokaryotic cells and viruses
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Compare prokaryotic and eukaryotic cells
Eukaryotic cells are larger and have a nucleus bounded by nuclear membranes (nuclear envelope) prokaryotic cells are smaller and have no nucleus or nuclear envelope
Describe the characteristics of bacteria, why are they successful What size are they
They occur in every habitat in the world so are versatile, adaptable, and very successful Lots of success comes from their small size from 0.1 to 10qm in length
What is a bacterial cell wall made of How do bacteria protect it
Murein, a polymer of polysaccharides and peptides Most bacteria further protect themselves by secreting a capsule of mucilaginous slime around this wall
What does the cell wall do in bacteria How thick is it
Physical barrier that excludes certain substances and protects against mechanical damage and osmotic lysis It is 10-80nm thick and is made of murein
What does the capsule in bacteria do
Capsule is a slimy layer around the murein cell wall of bacteria, and it is made of protein. It covers the antigens to help stop bacteria producing an immune response in the host cell It prevents bacteria from drying out (dissetation) Protects bacterium from other cells and helps groups of bacteria stick together for further protection
What does the cell surface membrane do in bacteria
It is inside the cell wall, acts as a differentially permeable layer which controls the entry and exit of chemicals
What is found in the cytoplasm of bacteria
Cytoplasm is jelly like fluid which contains enzymes and other soluble materials It contains 70s ribosomes, which are smaller than those in the cytoplasm of eukaryotic cells (80s) but they still synthesise proteins
How do bacteria store food reserves
Glycogen granules and oil droplets
How is DNA in bacteria structured
The genetic material in bacteria is stored in a circular stand of DNA. So not in nucleus. Also found in plasmids It possesses the genetic information for the replication of cells
What are plasmids in bacteria, what do they do how do they reproduce How are they used in genetic engineering
They are small circular pieces of DNA They possess genes that may aid the survival of bacteria in adverse conditions eg produce enzymes that break down antibiotics They can reproduce themselves independently and may give bacteria resistance to harmful chemicals They are used extensively as vectors (carriers of genetic info) in genetic engineering
Outline 4 key differences between prokaryotic and eukaryotic cells
Cell wall of prokaryotes is made of murein whilst cell wall of eukaryotes is made of cellulose Prokaryotic cells dont have a nucleus they have a circular strand of DNA whilst eukaryotes have a nucleus with a nuclear envelope Prokaryotes have no membrane bound organelles whilst eukaryotes do eg mitochondria Prokaryotes DNA is not associated with protein whilst Eukaryotes is associated with proteins called histones
What are flagellum in bacteria
Like a tail at the back of it, bacteria can have one or several used for locomotion, but only in certain species It also enables movement
What are viruses How big are they
They are acellular, non living particles They are smaller than bacteria and range in size from 20-300nm
What is a viruses genetic material stored as What do capsids do
. They contain nucleic acids such as DNA or RNA The nucleic acids are enclosed within a protein coat/shell called a capsid to protect the viral genome
Some viruses are surrounded by a further lipid envelope What attaches to these, or the capsid if they are not present
Attachment proteins which are essential to allow the virus to identify and attach to a host cell