Bacteria and viruses

Cell wall

A physical barrier made up of murein that excludes certain substances, protects against mechanical damage and osmotic lysis.

Capsule

Protects bacterium from other cells and helps groups of bacteria to stick together for further protection

Cell surface membrane

Acts as a differentially permeable layer, which controls the entry and exit of chemicals

Circular DNA

Posesses the genetic information for the replication of bacterial cells

Plasmids

Posesses genes that may aid the survival of bacteria in adverse conditions, e.g. produces enzymes that break down antibiotics

Differences from eukaryotic cells

-Cytoplasm lacks membrane-bound organelles

-Smaller ribosomes

-No nucleus

-A cell wall that contains murein, a glycoprotein

-One or more plasmids

-A capsule surrounding the cell

-One or more flagella

Structure of viruses

ALL viruses have :

-Genetic material

-Capsid

SOME viruses have :

-Envelop

-Glycoproteins

-Enzymes

Genetic materials in viruses

-DNA or RNA

-Single or double stranded

-Contain instructions for making new viruses

Capsid

Protein layer that protects genetic material

Envelop

Outer layer of phospholipids that helps viruses enter host cells

Glycoproteins

Sometimes called surface attachments or envelop proteins. Attached to envelop and helps viruses to bind to the surface of the host cells

Enzymes

-Reverse transcriptase in HIV

-Helps to convert viral RNA in DNA

-Allows virus to integrate genetic material into host’s DNA

Virus replication stages

-Viruses attach to host cell using attachment proteins

-Virus injects genetic materials into host cell

-Virus uses host cell’s enzymes and ribosomes to replicate viral proteins

-New viral particles released from host cells

-New viruses go onto inject more cells

Structure of HIV

HIV replication stages

-Attachment protein binds to CD4 on a helper T cell

-RNA and the enzymes of HIV enters the helper T cell

-Reverse transcriptase converts RNA to DNA

-Newly made DNA inserts into the helper T cell’s DNA

-Viral mRNA produced

-Viral proteins produced

-HIV assembles and leaves the cell