topic 2 - prokaryotic cells and viruses Flashcards
cgp (topic 2A) 30 - 31
what is a prokaryotic cell
smaller, simpler cells that do not have a nucleus
what 7 organelles are found in a prokaryotic cell
(1) cytoplasm
(2) flagellum
(3) circular DNA
(4) Plasmids
(5) capsule
(6) cell wall
(7) plasma membrane
how is a cytoplasm in a prokaryotic cells different to a cytoplasm in a eukaryotic cell
it has no membrane bound organelle (unlike a eukaryotic cell) - it has ribosomes, but they’re smaller than those in a eukaryotic cell
what is the flagellum
a long, hair like structure that rotates to make the prokaryotes cell move - not all prokaryotes have a flagellum and some have more than one
where does the DNA float freely
in the cytoplasm
how is the circular DNA presented
as a long coiled up strand and is not attached to any histone proteins
what are plasmids, what do they contain
small loops of DNA that can reproduce independently and aren’t part of the main circular DNA molecule - they contain genes for things like antibiotics resistance and can be passed between prokaryotes
what is a capsule made from and what does it do
it’s made up of secreted slime - helps to protect bacteria from attack by cells of the immune system
what is a cell wall made from and what does it do
from a polymer called murein which is a glycoprotein - supports the cell and prevents it from changing shape
what is a glycoprotein
a protein with a carbohydrate attached
what is a plasma membrane made from and what does it do
made of lipids and proteins - it controls the movement of substances into and out of the cell
why are viruses not cells
because they are just nucleic acids surrounded by protein - they’re not alive
what three things do bacteria have that viruses don’t
plasma membrane, cytoplasm, ribosome
what is a host cell
a cell that serves as a shelter and a food source to a foreign organism
what are 3 features of a virus
(1) core of genetic material
(2) capsid
(3) attachment protein
what are the two possibilities of genetic material a virus may contain
DNA or RNA
what is the capsid
the protein coat around the core
where are the attachment proteins present
sticking out from the edge of the capsids
what do the attachment proteins do
they allow the virus bind onto a suitable host cell in order to infect them
what is an example of a feature some viruses may have
lipid envelope
are viruses bigger or smaller than bacteria
smaller
how to prokaryotes replicate
by binary fission
what is binary fission
a type of asexual reproduction where the cell replicates its genetic material before physically splitting into two daughter cells
what is the first step of binary fission
the circular DNA and plasmids replicate - the main DNA loop is only replicated once but plasmids can be replicated many times
what is the second step of binary fission
the cell gets bigger and the DNA loop move to opposite ‘poles’ of the cell
what is the third step of binary fission
the cytoplasm begins to divide and new cell walls begin to form
what is the fourth step of binary fission
the cytoplasm divides and two daughter cells are produced - each daughter cell has one copy of the circular DNA but can have a variable number of copies of the plasmids
what do viruses use to replicate themselves
host cells
why can some viruses only infect one type of cell
because different viruses have different attachment proteins so require different receptor proteins on host cells
how do viruses bind to host cells
they use their attachment proteins to bind to complementary receptor proteins on the surface of host cells
why don’t viruses undergo cell division, what do they do instead
because they aren’t alive - instead they inject their DNA and RNA into the host cell - the infected cell then replicates the viral particles
