6.2 Cause of death Flashcards
Tuberculosis, TB
Disease caused by
Mycobacterium tuberculosis. Most infections
occur in the lungs, a condition known as
pulmonary TB. Lung tissue is damaged causing
symptoms such as cough, shortness of breath,
fever and fatigue. The bacteria can spread from
the lungs to other areas of the body such as the
nervous and lymphatic system. Here the
infection is known as glandular TB because one
of the main symptoms is swollen lymph glands.
HIV
HIV (Human Immunodeficiency Virus)
attacks T cells and destroys parts of the human
immune system, causing AIDS (Acquired
Immune Deficiency Syndrome).
Bacteria, Bacterium
Bacteria are
microorganisms. They are economically very
important. Not only do they cause many diseases
but they also play a vital role in recycling
chemical elements such as carbon, and they can
be genetically modified to make a number of
useful substances. Bacterial cells are
prokaryotic cells. They do not have a nucleus
or membrane-bound organelles such as
mitochondria. Each cell is surrounded by a cell
wall and is also very small in size.
Bacterial cell wall
Does not contain cellulose; made of peptidoglycan: a polysaccharide cross-linked by peptide chains. Gram-positive bacteria have walls that are thickened with additional polysaccharides and proteins. Gram negative bacteria have thinner walls but with a surface layer of lipids for protection.
Capsule
Capsule is a term with different
meanings. In some bacteria, a capsule is a layer
which may be found outside the cell wall. In
plants, a capsule is a type of fruit; when it is
ripe, seeds are shaken out through small
openings in its wall. The fruit of a poppy is a
capsule.
Flagellum, Flagella
A long thin hair-like process
found on some bacteria. Flagella rotate and
allow bacterial cells to move.
mesosome
infolding of bacteria cell surface membrane
Plasmid
A small, circular piece of DNA found in
the cells of many bacteria. Plasmids can be
transferred from one cell to another. They are
very useful in genetic engineering because they
can be used to insert new genes into the cells of
bacteria and plants.
Pili
Very thin filaments found on the surface of
some bacteria. Pili have various functions.
Some transfer DNA between bacterial cells;
others allow bacterial cells to bind to each other
or to foreign cells.
Ribosome
A small organelle made of RNA and
protein found either free in the cytoplasm or
attached to the membranes of the rough
endoplasmic reticulum. Protein synthesis takes
place on ribosomes.
Virus
An extremely small particle which is only
capable of replicating once it is inside a living
cell. A virus consists of a nucleic acid molecule
surrounded by a protein coat. Some large
viruses also have an outer lipid layer. Outside
the cell of its host, a virus is completely inert. It
cannot feed, respire or multiply, so it is best
regarded as non-living.
Host
A host organism is one that is infected by a
parasite. Humans, for example are the hosts of
malarial parasites and tapeworms. Other
parasites include bacteria such as those which
cause food poisoning and tonsillitis, and viruses such the genital wart virus which may lead to
cervical cancer.
Lysis
Lysis of cells involves the destruction of
cells by damage to the cell surface membrane
and the escape of the cell contents. Viruses
escape from their host cells by lysis.
Antigen
A molecule of a substance that the body
regards as foreign or harmful. The presence of a
particular antigen produces the specific immune
response by white blood cells called lymphocytes. There are two types of
lymphocyte cells, B cells and T cells. B cells
produce antibodies in response to antigen. T
helper cells and T killer cells are activated by
the presence of antigens.
The presence of a
particular antigen causes white blood cells
called lymphocytes to produce the
corresponding antibody.
For example, the virus
which causes measles has antigens on its
surface. If a person gets measles, these antigens
cause the lymphocytes to produce measles
antibodies. These antibodies help the person to
overcome the infection and recover.
Pathogen
A general term used to describe a
microorganism that causes disease.
Campylobacter and Helicobacter are examples
of pathogenic bacteria. Viruses are also
pathogens, as are the fungi which cause diseases
such as athlete’s foot and thrush.
