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C10 EXISTING CELLS ARE
THE PRODUCTS OF EVOLUTION
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People naturally question the origins of life
General agreement that our planet is 4.5 billion
years ago
Atmosphere was water vapour, carbon dioxide,
nitrogen, methane and ammonia gas
Warmer temps/lost of volcanic activity
Many electrical storms
1953- Stanley Miller- mixed the above gases and
controlled temps as above and produced organic
molecules
◦ Amino acids, nucleotides and ATP
◦ SOME SPONATNEOUSLY POLYMERISED AND /OR JOINED
TOGETHER
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Other scientists later showed that when these
molecules mixed in the presence of lipids
some organisations/membranes formed
Supports the idea that simple cellular
structures capable of reproduction could have
occurred
Earliest form of life the Stromatolites- 3
billion years ago-fossilised remains of
photosynthetic prokaryotes
Found along coastlines- bacterial matsautotrophic- therefore produce oxygenadded this to the atmosphere
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Oldest eukaryotes-protists
Two main groups:
◦ Protozoa
◦ Algae
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Many forms still exist today
Live generally aquatic environments
Widely believed that eukaryotic cells
originated as a collection, community of
prokaryotes
Development to eukaryotes in involved two
steps….
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Infolding of the plasma membrane to form an
endo- membrane system-formed the
endoplasmic reticulum and most other
organelles, i.e nucleus and golgi bodies
2nd- endosymbiosis- means that close
organisms/living in close proximity were
taken in or incorporated into other organisms
The chloroplasts and mitochondria seem to
have evolved from small prokaryotes that
were engulfed by endosymbiosis into larger
prokaryotes
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Thought to have been heterotrophic cells able
to use oxygen in aerobic respiration-release
energy
CHLOROPLASTS:
◦ Evolved from autotrophic cells capable of using
light energy to produce food and release oxygen
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Evidence to support these theories is that:
◦ Both mitochondria and chloroplast are similar to
eubacteria which exists today
◦ Both have double membranes-originating from the
original prokaryote and the host cell membrane
◦ Both have ribosomes, DNA and RNA- self
replicating
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C11 Human beings culture cells for a
variety of purposes
C11.1- Understand techniques of cell
culture and discuss some contemporary
examples of their use
◦ Cells can be grown successfully in the lab
◦ These are referred to as cell cultures
◦ Variations are evident for plant or animal
cells
◦ Following is a general procedure.
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1. tissue of interest is dissected and cells of
same type exposed
2.A protein digesting enzyme (proteolytic
chemicals) are added to digest the
intracellular matrix of the connective tissue
and release the cells
3. the cells are then placed in a culture
medium- with correct sugars and salts and
sometimes antibiotics to prevent bacterial
growth
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Culture is kept in a flat flask
At the right/optimum temperature (37 for
human cells)
Cells grow quickly and can be easily removed
for investigation/research
They can only grow to about 40 generationsthe Hayflick Limit
LAB or in-vitro techniques enable us to store
cells for many years
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Shortens generation time for plant
breeding/improves productivity
Can be used to grow human tissue i.e for
burns victims-and possibly organs in the
future
Bioethics is the term used when talking about
peoples beliefs or arguments for and against
such techniques
◦ the biggest controversy being IVF and keeping
embryo's to research or discarding them and not
implanting them all
◦ Or growing one in the lab completely/not in a
uterus
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C12.1 Discuss possible benefits and/or
harmful effects of chemicals that human
beings use
◦ The four groups which affect humans either
beneficially or detrimentally are:
◦ Drugs:
 Any chemical/substance that alters normal functioning
 Medical drugs treat disease or injury –antibiotics etc
 Non Medical:
 Nicotine and alcohol
 Both have deleterious effects on cells in high
concentrations
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Alcohol- effects cell metabolism- leads to
cirrhosis of the liver
◦ Cell death
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Illegal Drugs:
◦ Marihuana, heroin, cocaine, amphetamines, ecstasy
◦ All effect cell activity- particularly nerve cells
◦ Interact with other chemicals in the body
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Recently new antiviral drugs- Zanamivir- for
the flu
Works b y blocking the active site of the
enzyme neuraminidase –crucial to the
replication of the virus
Hoped to be available by a puffer-like asthma
inhalers
Not a trial and error drug- fits exactly
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More to come
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Blood pressure
Pain
Cholesterol levels etc
All can have issues if not used as prescription
states and if not us e by the rightful patient
Overuse of antibiotics led to the multiresistant strain of Staphylococcus aureus
Some are addictive or lead to psychological
disorders
Petrol, gas and coal
 When burnt with oxygen produce
carbon dioxide or monoxide that
accumulate in atmosphere
 If breathed in affect cell metabolism Carbon monoxide combines with
haemoglobin as well as oxygen doesaffects cellular respiration- then the
person dies
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Inorganic fertilizers
◦ Boost crop production
◦ Detrimental effects occur as they are
soluble in water and move through
underground dams and would cause many
issues- i.e increased dissolved salts in the
soil= more algae growth or “blooms” in
the rivers and sea
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Arsenic
Cyanide
◦ Metabolic poisons
◦ Act as inhibitors of enzymes- block or compete for
active sites
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Burning tobacco – greater number of harmful
chemicals
Insecticides- used to kill pests but overuse
creates resistance as with bacteria
Some last a long time in the soil and keep
causing problems pg 105
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RISK-need to clean up chemicals that pollute
air/water etc. but how/ otherwise risk is high