Download Micro-organisms

Micro-organisms
Bacteria: are simple, single celled organisms.
They can have many different shapes: Coccus which is spherical,
spirillum, which is a spiral shape and bacillus, which is a rod shape.
The structure of bacteria:
Often, the bacterium (single bacteria) has a capsule around the
outside cell wall. This capsule prevents dehydration of the cell.
The cell wall maintains the shape of the cell.
The cell membrane controls what goes in and out of the cell, it is semi
permeable so molecules can diffuse through. The cell membrane can
also detect changes in the surroundings and respond to them.
Nucleus: contains nuclear material (funny that).
Feeding:
Bacteria feed by decomposing matter.
1) Enzymes are secreted through the cell membrane onto food.
2) Enzymes break down food into smaller molecules
3) The small molecules are absorbed through the cell membrane
Reproduction:
Bacteria reproduce by binary fission. Binary fission is the process of
'splitting into two'.
(if you want more detail on this, ask)
The ideal conditions for bacterial reproduction are a moist and warm
area. If there are such ideal conditions, the bacteria will multiply
rapidly.
A lack of food and a build up of toxic wastes, will eventually cause
bacteria numbers to decline. These toxic wastes can be things such as
carbon monoxide, which is produced when anaerobic respiration
occurs, or things such as the bacteria's own waste products.
Fungi:
Fungi do not contain chlorophyll, so they cannot produce their own
food.
There are three main types of fungi...
Yeasts; they're single celled.
Moulds; they're thin threads.
Mushrooms; they're large fungi.
Mould structure:
Have hyphae which are thin threads that grow into food.
Has a sporangium which holds reproductive spores.
Fungi feed by decomposing matter.
The hyphae secrete enzymes from the tips into the food, these
enzymes break the food down into smaller pieces which are then
consumed by the fungi.
Fungi consume either dead material, or alive matter.
The fungi that consume dead material are called saprophytic fungi.
The fungi that consume alive material are called parasitic fungi. They
feed off living plant of animal tissue.
Reproduction.
The desirable conditions for fungi growth and reproduction are similar
to those of bacteria: a warm, moist area.
1) Inside the sporangium are many spores, these spores are released
into the air.
2) When the spore lands on a food supply, the new hyphae grow.
Viruses-the smallest of micro organisms
Viruses are not technically alive because they do not feed or respire.
The purpose of a virus is solely to reproduce.
Structure:
The general structure of a virus is an outer protein coat, this is for
protection. This protein coat reacts with specific cell types.
Housed inside of this protein coat is nuclear material(DNA). The DNA is
the genetic information containing how to reproduce these viruses.
Reproduction:
1) Virus attaches itself to the host cell and injects the DNA into the
host cell.
2) The DNA instructs the cell to produce more copies of the virus.
3) Cell ruptures. A large amount of viruses are released to infect other
cells.
Micro organisms (pros and cons)
There are a large number of micro organisms that are helpful.
Helpful microbes:
Decomposers:
Bacteria and fungi break down matter releasing nutrients, e.g.
nitrogen (this plays an important role in the nitrogen cycle; you should
be familiar with this)
Nitrogen fixing bacteria:
In the soil there is nitrogen fixing bacteria. These bacteria are very
important as they convert the nitrogen in the air into the nitrates
required by plants for making proteins.
Denitrifying bacteria:
These bacteria convert nitrogen compounds into nitrogen, which is
released into the air.
Food production:
Bacteria are used in the production of many things such as cheese and
yoghurt.
Yeast, which is a fungus, is used to make bread and to produce alcohol
by fermentation (anaerobic respiration).
Food source:
Fungi such as mushrooms are edible.
Harmful (pathogenic) microbes:
Pathogenic microbes can enter the body, feed and reproduce. In the
process of reproduction tissue is broken down and toxins are produced
which can lead to diseases.
All viruses are pathogenic because the host cell is damaged.
Examples of
Bacterial diseases:
Meningitis, syphilis, tuberculosis and salmonella (food poisoning).
Fungal diseases:
E.g. ringworm, thrush and athlete’s foot.
Viral diseases:
Aids, measles and influenza.
The bodies’ defenses:
Skin-Provides a barrier to pathogens. Our ears, eyes and nose are
protected by a layer of mucus (yummy).
Phagocytes, which are white blood cells, engulf pathogens and digest
them.
Lymphocytes which are another form of white blood cells, produce
antibodies which destroy specific pathogens.
Vaccinations are weakened of dead pathogens that are injected into
the body these stimulate the lymphocytes to produce antibodies for
this particular pathogen, which provides immunity.
Chemical defenses!
Disinfectants: Strong chemicals used to kill microbes on floors, around
the home and in hospitals.
Antiseptics: These are weaker chemicals used to kill microbes on living
tissue. They’re weaker as we do not want to harm the tissues, as some
stronger chemicals could.
Antibiotics:
These are a form of oral medication, which kill bacteria internally, but
do not harm any living tissue.
Factors affecting micro organisms:
Temperature:
Micro organisms prefer warm temperatures. At high temperatures the
micro organisms can be killed off.
In colder temperatures, the life functions of the micro organisms slow
down considerably.
Ph-Micro organisms prefer a neutral area (PH of around 7), as a strong
basic or acidic environment can either kill the micro organisms or
prevent their life processes from occurring properly.
Nutrients-Micro organisms require nutrients to carry out life processes
(viruses do not as they do not feed). An area where there is a plentiful
supply of nutrients is desired.
Oxygen availability-As both fungi and bacteria respire, a readily available
source of oxygen is important. There are special cases, where some
bacteria are specifically designed to respire anaerobically (without
oxygen), aerobic respiration is much more efficient, and so, in general,
an area with a plentiful supply of oxygen is desired.
Terms you need to know:
Inoculate- To introduce a micro organism to a culture medium
Enzyme- A protein that catalyses specific chemical reactions.
Pathogen- An organism that causes a disease.
Saprophyte- An organism that feeds off dead matter.
Aerobic- Respiration in the presence of oxygen.
Anaerobic- Respiration without the presence of (enough) oxygen.
Hyphae- The fine threads of fungi, which grow into the food.
Spores- Small single celled reproductive body which can grow into a
larger organism (in your cause it will grow into a fungi)
Toxin- A poisonous substance produced my organisms (such as
bacteria and fungi) which can cause disease when introduced to body
tissue.
Disinfectant- A strong chemical used to kill microbes on floors, around
the home and in hospitals.
Antibiotic- These are a form of oral medication, which kill bacteria
internally, but do not harm any living tissue.
Moving right onto genetics (yay I love genetics hahah)
Genetic code!
Now, people sometimes get confused with genes and alleles, I’ll try to
clarify things up as I go! Bare with me.
Okay, so:
Cells are the building blocks off life. Inside the cell is a nucleus, which
stores chromosomes. Specific sections of chromosomes are called
genes. Genes are lengths of the DNA molecule.
Cells-->nucleus-->chromosome- ->genes(made up of DNA)
Alleles are the different forms a gene can take. IE the GENE for eye
colour, can either be blue(b) or Brown (B).
Blue and brown are the possible alleles of the gene for eye colour.
(Trust me it’s frustrating when people in year 12 biology get those
confused!).
Each gene gives instructions for a characteristic of the organism.
Chromosomes: in different species the number of chromosomes varies.
Humans have 46 chromosomes, made up of 23 pairs.
Homologous pair: carry the same set of genes. One set is inherited from
your father and one from your mother.
The gene for each characteristic is represented by two alleles (one
from mum one from dad).
Cell division:
Before cell division the DNA must replicate itself.
1) The DNA unzips
2) Spare bases match up with each strand to complete the sequence
3) Yay there is now two copies of the DNA (one for each of the cells
going to be produced)
Bases which go together:
Adenine
Guanine
Cytosine
Thymine
Adenine goes with guanine and cytosine goes with thymine
I remember this by thinking ‘AT Good Charlotte’
“AT” and “GC”
Mitosis:
Mitosis occurs in all cells except when producing sex cells.
The purpose of mitosis is to produce identical cells for growth and
replacement of old cells.
Mitosis results in two genetically identical cells each with the full
number of chromosomes.
Meiosis:
Meiosis occurs when producing sex cells (gametes)
Meiosis results in four genetically unique gametes each with half the
full number of chromosomes.
Chromosomes replicate, genetic information is exchanged and mixed
during two cell divisions. (If you need more detail on this ask, but this
is getting long so I’m just briefing it up!)
The random mixing of the genetic information gives variation in
species which is necessary for survival.
Variation:
Alleles are the different forms genes can take.
Physical (phenotypes) characteristics are controlled by genes.
A dominant characteristic is always labeled with a capital letter. The
dominant characteristic is always expressed if that allele is present
(even if only one is present).
A recessive characteristic is always labeled with a lowercase letter. A
recessive characteristic is only expressed if both alleles are recessive
(homozygous).
Genotype is the specific combination of inherited alleles, e.g. Bb or BB
or bb
Phenotype is what we see, the physical characteristic. E.g. blue eyes
Homozygous: The genotype can be described as homozygous if both
alleles are the same, e.g. BB or bb
Heterozygous: the genotype can be described as heterozygous if both
alleles are different, e.g. Bb
Fertilization:
Meiosis in parents produces sex cells (gametes) with only one allele for
each characteristic.
These gametes fuse to produce a zygote. The zygote gets one allele
from each gamete.
How to estimate the proportion of offspring with a characteristic:
We use punnet squares… This is sort of hard to explain via notes, so if
you would like someone to go through these just ask ok.
Pure breeding: occurs when two homozygous parents breed.
Application of genetics:
Selective breeding: This is basically when two animals are specifically bred
together because they both have desirable genes. For example, in the
milking industry, a cow which produces a large amount of milk is more
desirable, so this cow will be mated will a bull that had a mother who
was also able to produce a large amount of milk. This would result in
many, if not all, of the female offspring being able to produce large
amounts of milk.
Cloning:
Occurs when an organism is genetically identical to and descended
from another organism. Ok, it’s not all about sheep though. Apples
have been cloned, certain apple types are more desirable and these
apple trees have had clippings taken off them, and then they have
been replanted. By doing so you’re able to produce identical trees,
which will produce the same apples!
Genetic modification: any alteration of genetic material, as in agriculture,
to make them capable of producing new substances or performing new
functions.