OCR AS Prokaryotic and Eukaryotic Cells

OCR AS Prokaryotic and Eukaryotic Cells

1. Prokaryotic Cells

   • Much smaller - <5um
   • no membrane-bound organelles such as mitochondria, ER and chloroplasts
   • surrounded by peptidoglycan cell walls
     • made of murein
   • ribosomes are far smaller at 20nm in diamter
   • DNA is in the form of a single loop
   • the general area in which plasmid DNA is found is called the nucleoid
   • ATP is produced in mesosomes - infolded regions on the CSM
   • some have flagella which use ATP to rotate a disc at the base attached by a hook to the spiral protein
   • cell division by binary fission
   • thick capsule layer made of polysaccharides
   • Gram-negative bacteria have two membranes - the peptidoglycan layer is thinner but outside it is a thin layer of lipoprotein and then a second outer membrane made of lipopolysaccharides.
   • no cytoskeleton

2. Eukaryotic

   • Around 30nm in diameter
   • Contain linear chromosomes, and the DNA is associated with histones
   • some have undulipodia which consist of a cylinder of 9 microtubules with two in the middle - use ATP
   • most contain two copies of each gene - diploid
   • always have a cytoskeleton
   • distinct nucleus surrounded by a nuclear envelope. Chromatin is found inside the nucleus which condenses into chromosomes during DNA replication
   • plant cells have cell walls made of cellulose, pectin and hemicellulose