Prokaryotic Cells Flashcards
what is a prokaryote
a single celled organism whose DNA is free floating in the cytoplasm without a nucleus
what does prokaryote mean and what does this suggest
prokaryotic means before nucleus. this suggests they were around before eukaryotes
what are the two types of prokaryotes
bacteria and archaea
what is archaea
they are found in extreme environments
what are the similarities between eukaryotic and prokaryotic cells
they have a plasma membrane, cytoplasm, ribosomes for assembling amino acids into proteins and genetic material (DNA & RNA)
what are the differences between eukaryotic and prokaryotic cells
- prokaryotes lack a nucleus and membrane bound organelles while eukaryotic cells have a nucleus and membrane bound organelles
- eukaryotes are more complex and larger than prokaryotes
- prokaryotes have a much less well developed cytoskeleton with no centrioles, smaller ribosomes and have a cell wall made of peptidoglycan and not cellulose
- have naked DNA that’s not wound around histone proteins but floats in the cytoplasm in a loop (not a linear chromosome
what are the structures that are always present in prokaryotic cells
- RNA and ribosomes
- cell wall
- plasma membrane
- circular DNA
- cytoplasm
- nucleoid
what are the additional structures that are always present in prokaryotic cells
- pilli
- plasmid
- capsule
- mesosome
- flagellum
describe the RNA and ribosomes
ribosomes in prokaryotic cells (70S) are smaller than those in eukaryotic cells (80S). they are essential for protein synthesis with 70S ribosomes forming simpler proteins
how is ribosomal structure similar in prokaryotic and eukaryotic cells
- organised into large and small subunit (prokaryotic ribosomes contain over 50 different types of protein and those of eukaryotic cells contain more than 80 different types of protein)
- large subunit contains two different ribosomal RNAs in prokaryotes and 3 in eukaryotes while the small subunit contain one ribosomal RNA
- the larger 80S eukaryotic ribosome settles out at a faster rate in a solution or first in sedimentation. the 80S ribosomes are possibly involved in the production of more complex proteins
describe the cell wall
made of peptidoglycan - a cross linked polymer made of amino acids and sugars
how does the cell wall of prokaryotes differ from plant cells
prokaryotic cells have a cell wall made from peptidoglycan also known as murein. it is a complex polymer formed from amino acids and sugars.
in eukaryotes, the cell wall is made from cellulos
describe the plasma membrane
encloses the cell, regulating the movement of substances in and out
describe the DNA
it is circular. a single supercoiled loop of DNA, located in the nucleoid region
how does the DNA differ from eukaryotic cells
the structure of the DNA contained within prokaryotes but is packaged differently.
prokaryotes generally only have one molecules of DNA - a chromosome which is supercoiled to make it more compact. the genes on the chromosome are often grouped into operons meaning a number of genes are switched on or off at the same time
describe the cytoplasm
the gel-like substance filling the cell where various cellular processes occur
describe the nucleoid
the region within the cytoplasm where the DNA is positioned
what are pilli
small hair like projections that enable attachment to surfaces or other cells involved in sexual reproduction by transferring plasmid DNA
what is a plasmid
small, circular DNA molecules that replicate independantly and can carry advantageous genes like antibiotic resistance
what are plasmids used for
they are replicated independantly of a bacteriums genophore (during bacterial conjugation) and may confer an advantage such as antibiotic resistance.
used in genetic engineering to make copies of genes or large quantities of proteins or hormones
what is a capsule
a protective, waxy layer surrounding the cell wall, shielding bacteria from immune attacks and dessication. they are composed of polysaccharides and have water to protect from dessication
what is a mesosome
an infolding of the plasma membrane associated with DNA during cell division aiding in cell wall formation.
what are flagellum
a long, whip-like structure used for movement powered by protein motors allowing bacteria to move efficiently
how does the flagella differ from eukaryotic cells
prokaryotic flagellum have a thinner structure, rotated by a molecular motor, anchored by a basal body, the filament moves in a whip like movement which propels the cell and the energy to rotate is from chemiosmosis
eukaryotic flagellum have a 9+2 structural arrangement, each microtubule is composed at the protein tubulin, the energy to rotate is from ATP, anchored to a cell by a basal body, and the coordinated sliding of microtubules confers movement
