structure of prokaryotic cells Flashcards
what are prokaryotic cells?
+ smaller than eukaryotic cells
+ cytoplasm lacks membrane bound organelles
+ smaller ribosomes (70s compared to 80s in eukaryotes)
+ lack a nucleus
+ contain a cell wall made from murein, a form of glycoprotein ( and not cellulose)
+ e.g bacterial cells and cyanobacteria
what is the plasma membrane?
+ made mostly from lipids and proteins
+ controls movement of substances into and out of a cell
what is DNA (nucleoid) ?
+ free floating as a long coiled strand
+ has no proteins attached to it
what is a plasmid?
+ small circular DNA contains genes (for things like antibiotic resistance)
+ not always present but some can have more of them than other cells
what is the mesosome?
+ folded region of the membrane
+ provides a large SA
+ contains bound enzymes required for respiration
what is the capsule?
+ thick polysaccharide layer
+ used for…
sticking cells together
a food reserve,
protection against outside chemicals,
protection against phagocytosis
what is the cell wall?
+ formed from a polymer and murein
+ two kinds of cell wall that can be identified using a ‘Gram stain’
Gram+ : thick wall and stain purple
Gram- : thick wall with an outer lipid layer and stain pink
what are ribosomes?
+ site of protein synthesis
+ these are not attached to any membranes and they are also smaller (70s) than those in eukaryotic cells
what is the bacterial flagellum?
+ helical shaped tail for cell movement
+ embedded into the membrane and is driven by a proton (H+) gradient
+ clockwise rotation= move forward
+ anticlockwise= chaotic spin
+ not all prokaryotes have one and some may have more than one
what is binary fission?
+ bacterial reproduction
+ asexual process
+ no exchange of genes
+ in the right conditions bacteria will divide every 20 mins
what are viruses?
+ acellular ( not made up of discrete cells or cannot split into cells)
+ they are not cells - just a nucleic acid
surrounded by a protein
+ non-living
+ neither prokaryotic nor eukaryotic
+ part of a separate category called obligate
intracellular parasites
+ smaller than bacteria
+ all viruses will invade and reproduce within a host cell
what is a viral genome?
+ nucleic acid - core genetic material in a virus made of either DNA or RNA
+ viruses are classified based on this ( DNA - virus and RNA = retrovirus)
what is the nucleoplasmid?
+ protein coat that surrounds the core genetic material of the virus
what is the envelope protein?
+ AKA attachment proteins
+ allow the virus to cling to a suitable host
what is the envelope?
+ determines the virus ability to attach to and enter host cells
