Topic 1: Cell Biology

Topic 1: Cell Biology

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Typical Prokaryotic Cell: Escherichia (E) coli

• Cell Wall - contains murein or peptidoglycan which is made up of polysaccharide (sugar) chains. It is cross-linked at regular intervals by amino acids. Cell Wall prevents the cell from bursting when water is absorbed via osmosis.
• Cell Surface Membrane - a semi-permeable membrane that surround the living material in the cell. The structure/ functions are the same as in Eukaryotes. It is also the site for some respiration enzymes. It forms mesosomes and or photosynthetic membranes .
• Mesosomes - infolds of the cell membrane. Organizes the separation of DNA in the two daughter molecules, after replication. It helps in the formation of cross-walls between the daughter cells. Site of Aerobic respiration.
• Photosynthetic Bacteria - sac-like, tubular or sheet like infolds with photosynthetic pigments.
• Capsules - slimy, gummy secretions of some bacteria. the secretions help bacteria to colonize and enable them to stick to surfaces and it offers additional protection for the bacteria.

Typical Prokaryotic Cell: Escherichia (E) coli

• Genetic Material - Bacterial DNA is a single circular molecule. It is made up of 5 million base pairs and is 1mm long. The total DNA (genome) is less than that of a eukaryote, thus the information is also less (genetic information).
• Ribosomes - Site of PROTEIN SYNTHESIS
• Flagella - Allows bacteria to be motile (movement due to metabolic energy). Propels the cell by rotating at its base in a corkscrew like motion.
• Pili - Numerous protein rods that project from some bacteria's walls. They are shorter than flagella and allows the attachment to other cells and surfaces
• Plasmids - additional to the strand of circular DNA is a plasmid, a small self-replicating circle containing extra DNA. It has only a few genes, which give extra survival advantage.