BISC300 Lecture Notes - Lecture 4: Protein Data Bank, Plasmid, Nucleoid
21 May 2018
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Lecture 4: Prokaryotic Cell and Endospores
Clicker Review
1. Capsule: organized space that surrounds bacterial cell, composed of polysaccharides
and difficult to separate from the cell, provides protection
2. Capsule of gram negative
3. Genes in bacteria are found in nucleoid region (bacterial chromosomes, circular)
Structures external to envelope
• Capsule
o Polysaccharides
o Organized, not easily removed
o Visible in light microscope
• Slime layer
• Glycocalyx
• Protective advantages:
o From desiccation
o From desiccation, detergents
o Excludes viruses
Cytoplasmic structures
• Plasmids: independently replicating, circular pieces of DNA, facilitates transfer of DNA to
another bacterial cell
o Extrachromosomal DNA
▪ Bacteria, archaea, some fungi
▪ Small, closed circular DNA molcules
▪ Replicate independently of chromosome
▪ Episomes: may integrate into chromosome
▪ Inherited during cell division
• Nucleoid:
o not membrane bound
o location of chromosome and associated proteins
o closed, circular, double stranded DNA molecule
• Plasmids
o Extrachromosomal DNA
▪ bacteria, archaea, some fungi
▪ small, closed circular DNA molecules
▪ replicate independently of chromosome
▪ episomes – may integrate into chromosome
▪ inherited during cell division
• Ribosomes:
o make proteins
o complex protein/RNA structures
o protein data bank
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