When you’ve got a sore throat, the cause doesn’t always seem

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95 L1 Bacteria & viruses 639w 4m

When you’ve got a sore throat, the 
cause doesn’t always seem 
important. Some microscopic 
nasty is waging war with your 
immune system, it hurts, and you just want to 
feel better. But whether it’s bacteria or a virus 
on the rampage is actually very important.
Bacteria are some of the smallest living 
things on the planet, each made from just a 
single, primitive cell. Their insides are 
separated from the outside by a fatty 
membrane and a flexible coat of armour called 
the cell wall. Their genetic information is 
carried on loops of DNA, and these contain 
tiny factories called ribosomes, which use the 
genetic code to produce the molecules that the 
bacteria need to grow, divide and survive.
Viruses, on the other hand, are not 
technically alive. They carry genetic 
information containing the instructions to 
build more virus particles, but they don’t have 
the equipment to make molecules themselves. 
To reproduce, they need to get inside a living 
cell and hijack its machinery, turning it into a 
virus factory.
Both bacteria and viruses can cause 
diseases, but knowing which is the culprit is 
critical to treating them effectively. Antibiotics 
can harm bacteria, but have no effect on 
viruses. Even your own immune system uses 
different tactics. For bacteria, it unleashes 
antibodies – projectile weapons that stick 
invading microbes together, slowing them 
down and marking them for destruction. For 
viruses, your immune system can search for 
any infected cells before initiating a self-
destruct sequence to dispose of anything 
lurking inside. But some viruses are able to 
endure our defences, and can remain inside 
us indefinitely.
& viruses
“Bacteria are 
some of the 
smallest living 
things, while 
viruses aren’t 
technically alive”
The flu virus is 
covered in molecules 
that help it to get 
inside cells
Antibiotics attack bacteria. They work 
by interrupting the way that the tiny 
cells divide, grow and repair. However, if 
an infection is caused by a virus, 
antibiotics won’t help. Viruses don’t 
work in the same way as bacteria, so 
antibiotics can’t help to fend them off. It 
might not seem like much of a problem, 
but every time antibiotics are used, it 
gives bacteria a chance to learn how to 
resist them. So every time a patient with 
a viral infection is given antibiotics, not 
only will they not get better, but any 
bacteria lurking in their bodies will have 
a chance to see the drug and develop 
defences against it.

Both are microscopic, but take a closer look and the differences become clear
HeAd to HeAd
Viral infections can be mild, 
such as the common cold, 
while others can be deadly, 
like Ebola and smallpox
Bacteria are responsible 
for many illnesses, from a 
sore throat to the plague
Not alive
Viruses do not possess the 
tools to make their own 
molecules, and are missing 
genes vital for life.
Protein coat
The virus’ genetic 
information is stored inside 
a protective covering of 
protein molecules.
Nucleic acid
Viruses carry genetic information
some in the form of DNA, and
others in the form of RNA.
Some viruses also 
have an outer 
envelope, often made 
from fat and protein.
Bacteria carry their genetic 
code on a chromosome 
made from DNA.
Cell membrane
The membrane helps to 
control what goes in and 
out of the bacterium.
These small loops of DNA 
can be transferred between 
bacterial cells.
Cell wall
Bacteria have a protective 
cell wall, which helps to 
maintain their structure.
These structures allow bacteria 
to make the molecules that 
they need to live.
Bacteria and viruses are different infective agents but both 
can make us ill. Bacteria are organisms and can survive on 
their own, whereas viruses aren’t considered to be alive 
and can only reproduce by hijacking organisms’ cells. 

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