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Cause of Death
Topic 6.2
Spec6ification Topic
 8 Distinguish between the structure of bacteria and viruses.
 Read pages 90-91
 What is a post mortem:
 examination after death to determine cause.
 George Watson and Nicki Overton
 What is an aneurysm?
 blood builds up in a section of the vessel, swells
 Q 6.21: Remember that Unit 4 and 5 can be synoptic
 What were the results of Nicky Overton’s post mortem?
Prokaryotic Cells
Viral Structure
Viral replication
Q6.3 Draw up a table of comparison to allow you to distinguish
.
between
the structure of bacteria and that of viruses-Use table
in booklet
Feature Bacteria
Type of
Prokaryotic cell
cell
Size
0.5–5 µm in diameter
Structur
e
Contain cytoplasm, a long circular strand of DNA,
plasmids, cell surface membrane, free ribosomes,
rigid cell wall containing polysaccharide murein.
May have mesosomes (infoldings of the cell
surface membrane where respiration occurs),
flagella and pili. Some have a capsule outside the
cell wall.
Reprod
uction
Reproduce asexually by binary fission; after
replication of the DNA they divide into identical
daughter cells. No sexual reproduction occurs in
animals, but cell-to-cell contact
through conjugation.
Viruses
Viruses are small organic
particles with a much simpler
structure than bacteria. No
proper cell structure.
20–400 nm in length; a wide
range of sizes and shapes.
A strand of nucleic acid (RNA or
DNA) enclosed within a protein
coat. May have an outer
envelope taken from the host
cell surface membrane but
containing glycoproteins from
the virus.
Enter the cells of the organisms they
infect (the host) and use host’s
metabolic systems to make more
viruses. The virus’s genetic material is
replicated, then the protein coat
synthesised. Newly formed virus
particles are released by budding from
the cell surface or lysis of the cell.
Revision
 Complete Activity 6.6a Prokaryotic Cell Structure
 Activity 6.06 Comparing Prokaryotes, Eukaryotes and Viruses
table
Gram positive bacteria
 Simpler cell wall
 Lots of peptidoglycan
 Stained violet after Gram stain, dye binds to peptidoglycan
 Less dangerous
 More susceptible to antibiotics
Gram negative bacteria
 Complex cell wall
 Less peptidoglycan
 2 membranes with peptidoglycan in between
 Outer membrane has lipopolysaccharides
 Stain red with Gram stain
 More pathogenic: lipopolysaccharides are often toxic
 More resistant to antibiotics
Gram positive and Gram negative
Bacteria
Binary fission
 No nucleus and no centromeres , no mitosis
 DNA double strand separates
 Each strand acts as template for replication
 The cell wall and plasma membrane start growing transversely from near
the middle of the dividing cell.
 The cell membrane then invaginates and splits the cell into two daughter
cells, separated by a newly grown cell plate.
Viruses
https://www.youtube.com/watch?v=uIut0oVWCEg
Pathogens: disease causing
 Bacteria: Give examples
 TB
 Salmonella
 E coli
 Staphylococcus
 Streptococcus
 Cholera
 Gonorrhoea
 Chlamydia
 Viruses:Give Examples
 HIV
 Flu
 Measles
 Chicken pox
 Adenovirus
 Ebola
 Herpes
 rubella
TB
 Read page 94
 How does the TB bacterium spread?
 TB pathogen spread through droplet infection
 What increases the risk of infection?
 Contact with infected people, poor diet, health, overcrowding
 How long can the bacterium survive in dry conditions?
 Up to a few weeks.
HIV
 Read page 95
 How can HIV be transmitted?
 Bodily fluids (except urine and saliva)
 What is the most common route of HIV infection?
 Unprotected sex
 What are other routes?
 Why are babies protected during most of the pregnancy if the mother
is HIV positive?
 Barriers in placenta between blood