Transcript Document

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Living and Growing
(OCR Gateway)
W Richards
The Weald School
B3a Molecules of Life
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A Typical Animal Cell
1) Cytoplasm - this is
where the reactions
happen and these are
controlled by enzymes
2) Nucleus –
controls the
cell’s activities
3) Cell Membrane –
controls what
comes in and out
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4) Ribosomes – protein
synthesis happens
here
5) Mitochondria energy is released
here and there are
LOTS of these in
the liver and
muscles
Genes, Chromosomes and DNA
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DNA
Some facts:
- Made up of paired bases
- Contain instructions on what a cell does, how the
organism should work etc
- The instructions are in the form of a code
- The code is made up from the four bases that
hold the two strands together
- The bases represent the order in which amino
acids are assembled to make proteins
- The sequence of bases determines the order in
which a cell makes amino acids, which turn into
proteins
- There are about 20 amino acids in all, and
different combinations produce different proteins
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Making proteins
1) DNA “unravels” and a copy of one strand is
made
2) The strand copy is made to produce RNA
3) The copy (with its code) then moves
towards the ribosome
4) The ribosome “decodes” the code which
tells the ribosome how to make the protein
5) Amino acids are then joined together to
form a polypeptide (protein)
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DNA
Task: Find out how the structure of DNA
was discovered, including:
1) An image of Crick and Watson with
their original model
2) A brief desciption of what Crick and
Watson did to discover DNA
3) How Franklin and Wilkins built on their
work
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Watson and Crick
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We discovered the structure of
DNA in 1953. We used data from
other scientists (such as X-ray
data showing that there were two
chains wound in a helix) to come up
with the double-helix structure.
However, our discovery was not
accepted by the scientific
community until other scientists
repeated and tested the work.
B3b Proteins and Mutations
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Proteins
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Proteins are basically long chains of amino acids:
Every different protein has its own number and sequence of
amino acids which results in differently shaped molecules with
different functions.
Some example proteins:
Name of protein
Function
Collagen
Give structure
Insulin
Hormones
Haemoglobin
Carrier molecules
Enzyme use in nature
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Enzymes are proteins that speed up chemical uses. Here are
two important natural uses for them:
Cells use glucose to generate
energy – this process is called
“respiration”. Respiration
happens in mitochodria and is
catalysed by enzymes.
Photosynthesis is
catalysed by enzymes
in the cells.
Introduction to Enzymes
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Enzymes are biological catalysts. They help the reactions
that occur in our bodies by controlling the rate of reaction.
An enzyme is basically a protein molecule
made up of long chains of amino acids. These
molecules are then “folded” to create a
certain shape with high “specificity”:
The enzyme’s shape helps another
molecule “fit” into it:
Enzyme
This shape can be destroyed by
high temperatures or the wrong
pH:
Substrate
The “Active Site”
Active site
Enzyme
Substrate
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Enzymes
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Enzymes work best in certain conditions:
Enzymes are
denatured
beyond 40OC
Enzyme
activity
400C
Temp
Could be
protease (found
in the stomach)
Could be amylase
(found in the
intestine)
pH
The “Q10” value is a way of measuring the change to the rate
of reaction:
Q10 =
Rate at higher temperature
Rate at lower temperature
pH
Mutations
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Cells contain a nucleus and the nucleus contains genes that
carry instructions for what that cell should do:
Genes
Some facts:
• Some genes are “switched off” and don’t do
anything in that cell
• Genes basically tell the cell which proteins they
should be producing
• Sometimes cells can “mutate” which may have a
harmful effect on the cell and can be caused by
natural or artificial means.
Mutations
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Mutations are changes in the base sequence of the DNA molecule. They
can be passed on to daughter cells through cell division. They will result in
the wrong proteins being produced.
Mutations can be caused by:
- Ionising radiation (UV, X-rays etc)
- Radioactive substances
- Certain chemicals
Effects:
- Mostly harmful
- Causes death or abnormality in reproductive cells
- Causes cancer in body cells
- Some CAN be neutral or even beneficial (e.g. the peppered moth)
B3c Respiration
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Respiration Introduction
I enjoy taking samples using quadrats. In
order to do this, I need energy. Where does
this energy come from?
Our energy comes from a process called
respiration, which basically involves turning
food and oxygen into energy and this
reaction is controlled by enzymes.
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(Aerobic) Respiration
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All living organisms have to move, _____, reproduce etc. Each
of these life processes needs ENERGY. ___________ is the
process our bodies use to produce this energy:
Glucose + oxygen
C6H12O6 + 6O2
water + carbon dioxide + ENERGY
6H2O + 6CO2 + ENERGY
The glucose we need comes from ______ and the oxygen from
_________. Water and carbon dioxide are breathed out.
The MAIN product of this equation is _________.
Respiration happens in _________ in cells.
Words – breathing, energy, grow, respiration, food,
mitochondria
Heart
rate/min
225
The Effect of Exercise
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Breathing
rate/min
Rest
Exercise
100
Recovery
175
75
125
50
75
25
5 mins
10 mins
15 mins
20 mins
During exercise the following things happen: heart rate increases,
breathing increases and arteries supplying muscles dilate. These three
things all help muscles to get the oxygen and glucose they need.
Muscles and exercise
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When we exercise our muscles are supplied with more oxygen
and glucose, increasing the rate of respiration.
Respiration results in the production
of ATP which is used as an energy
source in cells. This process requires
oxygen so the rate of respiration can
be measured by measuring the rate of
consumption of oxygen.
Carbon dioxide produced
RQ =
Oxygen used
The rate of respiration is controlled by
enzymes. What are enzymes affected
by?
Anaerobic respiration
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Unlike aerobic respiration, anaerobic respiration is when
energy is provided WITHOUT needing _________:
Glucose
lactic acid + a bit of energy
This happens when the body can’t provide oxygen quick enough
for __________ respiration to take place.
Anaerobic respiration produces energy much _______ than
aerobic respiration but only produces 1/20th as much.
Lactic acid is also produced, and this can build up in muscles
causing ______ and “excess post-exercise oxygen
consumption” (“EPOC”), which explains why breathing and
heart rates remain high after exercise.
Words – debt, oxygen, fatigue, aerobic, quicker
B3d Cell Division
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Single celled or multi-celled?
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Advantages of being single-celled:
Advantages of being multi-celled:
Disadvantages of being single-celled:
Disadvantages of being multi-celled:
Cell Growth
There are three ways in which a cell might “grow”:
1) Cell division:
2) Cell expansion:
3) Cell specialisation:
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Mitosis
Each daughter cell has
the same number of
chromosomes and genetic
information as the parent.
Mammal cells are
“diploid” – they have
two copies of each
chromosome
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Making DNA copies
2) New bases pair
up with the
exposed bases
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3) An enzyme
bonds these bases
together
4) Two identical
pieces of DNA
are formed
1) The double
helix unzips
Meiosis
Each daughter cell has half
the number of chromosomes
of the parent.
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Mitosis:
1.
Mitosis vs. Meiosis
Used for growth and repair of
cells
2. Used in asexual reproduction
3. Cells with identical number of
chromosomes and genetic
information are produced
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Meiosis:
1.
Used to produce gametes for
sexual reproduction
2. Each daughter cell has half the
number of chromosomes of the
parent
Sexual Reproduction
The human egg and
sperm cell (“ HAPLOID
GAMETES”) contain 23
chromosomes each and
are created by meiosis.
When fertilisation happens the
gametes fuse together to make a
single cell called a DIPLOID
ZYGOTE. The zygote has 46
chromosomes (23 pairs) and
continues to grow through mitosis.
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Eggs and sperm
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The female egg cell and the male sperm cell are examples of
____________ cells:
The ______ cell is
specialised in two ways:
Nucleus
The egg cell is basically
an enlarged cell with
massive _____ reserves
An acrosome that
releases enzymes
to ______ its way
through the egg
Strong tail for
________
Words – food, swimming, sperm, specialised, digest
B3e The Circulatory System
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The Circulatory system
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The circulatory system is responsible
for pumping ______ around the body.
We need blood to be taken around the
body because blood contains ________
and _______. These are needed so
that all the ____ in our bodies can
produce _____ through _________.
The main organs in the circulatory
system are the _____, the lungs and
the kidneys.
Words – energy, heart, blood, glucose,
respiration, oxygen, cells
The four parts of blood
1. RED BLOOD CELLS – contain haemoglobin
and carry ______ around the body. They
have no _______ and a large surface area.
2. PLATELETS – small bits of cells that lie
around waiting for a cut to happen so that
they can ____ (for a scab).
3. WHITE BLOOD CELLS – kill invading
_______ by producing _________ or
engulfing (“eating”) the microbe.
These three are all carried around by the
PLASMA (a straw-coloured liquid). Plasma
transports CO2 and ______ as well as
taking away waste products to the ______.
Words – antibodies, clot, kidneys,
oxygen, nucleus, glucose, microbes.
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The role of haemoglobin
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1) Red blood cells are
packed with haemoglobin.
When they are pumped to
the heart the haemoglobin
picks up oxygen
(“oxyhaemoglobin”)
2) After the oxygen and
glucose have been removed
for respiration the blood is
sent back to the heart and
then to the lungs to start
again
The Double Circulatory System
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1) Blood gets pumped
from the heart to the
lungs and picks up oxygen
Having a double circulatory
system enables mammals to
pump blood at higher pressure
and with a greater flow rate.
5) After the oxygen and
glucose have been removed
for respiration the blood is
sent back to the heart and
starts again
2) The blood is then
taken back to the
heart…
3) The heart pumps
the blood to the
intestine (where
oxygen and glucose
are removed)…
4) … and to the rest of
the body (where oxygen
is removed)
Arteries, veins and capillaries
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Arteries carry high pressure
blood away from the heart.
They have smaller lumen and
no valves.
Capillaries have thin walls
(one cell thick) to allow
glucose and oxygen to pass
through. Also used to
connect arteries to veins.
“Lumen”
Veins carry low pressure blood back to the
heart. They have thinner, less elastic walls and
have valves to prevent backflow of blood.
The Heart
1. Deoxygenated
blood (i.e. blood
without oxygen)
enters through the
vena cava into the
right atrium
2. It’s then pumped
through the tricuspid
valve into the right
ventricle
3. It’s then pumped
through the semi-lunar
valve up to the lungs
through the pulmonary
artery
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4. Oxygenated blood
from the lungs enters
through the
pulmonary vein into
the left atrium
5. It’s then pumped
through the bicuspid
valve into the left
ventricle
6. It’s then pumped
out of the aorta to
the rest of the
body
B3f Growth and Development
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Revision of a Typical Animal Cell
1) Cytoplasm - this is
where the reactions
happen and these are
controlled by enzymes
2) Nucleus –
controls the
cell’s activities
3) Cell Membrane –
controls what
comes in and out
4) Ribosomes – protein
synthesis happens
here
5) Mitochondria energy is released
here
A typical plant cell:
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Cell wall – made
of cellulose which
strengthens the cell
Cell membrane
– controls what
comes in and out
Large vacuole –
contains sap and
helps support the
cell
Chloroplasts (containing
chlorophyll) – this is needed
for photosynthesis
Nucleus – controls
what the cell does and
stores information
Cytoplasm –
Chemical reactions
happen here
Plant cells vs. Animal cells
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Both types of cell have these:
1) Cytoplasm
Only plant cells
have these:
4) Cell wall
2) Nucleus
5) Chloroplasts
3) Cell Membrane
6) Large Vacuole
Bacteria
Consider a bacteria cell in more detail:
Bacteria contain cytoplasm
and a membrane surrounded
by a cell wall. The genes are
NOT in a distinct nucleus and
bacterial cells do not have
mitochondria or chloroplasts.
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Measuring Plant Growth
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I’m bored of using
quadrats now. I think
I’ll measure the growth
of this plant instead.
How can I do it?
There are a number of ways to measure plant growth, including
measuring:
1) Length/height
2) Wet mass
3) Dry mass
What are the advantages and
disadvantages of each?
Measuring Human Growth
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Growth rate
(cm/year)
Age
Adult Stem Cells
It is also possible to
have adult stem cells –
these are unspecialised
cells that can become
specialised later (but
they can’t form ALL
types of cell)
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Adult stem cells can be
found in places like
bone marrow.
Ciliated
epithelial cell
White blood cell
Nerve cell
(neurone)
Egg cell (ovum)
Stem cell research
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Stem cells are cells that have not yet specialised:
Embryo
Egg and
sperm
These stem cells have the
potential to develop into
any kind of cell. The rest
of the embryo is
destroyed. Most of these
embryos come from
unused IVF treatments
unless the stem cells are
Cloned taken from bone marrow
embryos in adults.
The ethical issue:
Should these embryos be treated as humans?
Human Growth vs Plant Growth
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There are many differences between the way humans grow and
the way plants grow:
1.
Humans have two main stages
of growth: straight after
birth and during adolescence
2. Human growth occurs
throughout the human
1.
Plants grow continually and won’t
stop until they die
2. Plant cells retain their ability to
differentiate whereas animal cells
lose it at an early stage
3. Plant cell division is restricted to
areas called meristems
Plant Growth Introduction
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Plants grow due to their cells dividing through mitosis. The
cells then specialise into root hair cells, palisade cells etc.
Unlike animals, plants continue to grow for the rest of their
lives.
Plant Growth - Meristems
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Plant growth occurs in areas called meristems. These
meristems are “mitotically active”:
This meristem causes the
plant to grow upwards.
This meristem causes the
plant to grow in width.
Cells from the meristem behave like
stem cells – they can develop into
any kind of cell. Cloned plants can
be produced from these cells.
B3g New Genes for Old
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Selective breeding
I raise cows. Each type of
cow is good at a certain job.
The Friesian cow produces
large quantities of milk, the
Jersey cow produces very
nice milk and the Hereford
cow produces lot of beef.
If, for example, I want lots of milk
I would only breed Friesian cows
with each other – this is
SELECTIVE BREEDING. The only
trouble is that I’m reducing the
“gene pool” by doing this.
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Friesian
Jersey
Hereford
Examples of Selective Breeding
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Uses of Genetic Engineering
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“Genetic engineering” is the idea of transferring a gene from
one organism into another in order to give it extra features,
such as:
With genetic engineering I can
produce milk that contains:
• Extra protein
• Lower levels of cholesterol
• Human antibodies
Other current examples of genetic
engineering include transferring genes
from carrots that are involved in
humans producing vitamin A and
putting them into rice instead and
engineering crops that are resistant
to herbicides.
An example - Insulin
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Step 1: Using RESTRICTION
ENZYMES “cut out” the part of
the human chromosome that is
responsible for producing insulin.
Step 2: Using another restriction
enzyme cut open a ring of bacterial
DNA (a “plasmid”). Other enzymes
are then used to insert the piece of
human DNA into the plasmid.
Step 3: Place the plasmid into a bacterium
which will start to divide rapidly. As it
divides it will replicate the plasmid and
make millions of them, each with the
instruction to produce insulin. Commercial
quantities of insulin can then be produced.
Genetic Engineering
Should genetic engineering
be allowed?
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Gene Therapy
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Gene therapy is when diseases are treated by modifying a
person’s genome. For example, take cystic fibrosis:
1) Take a
disease-causing
virus
2) Remove the
genetic material
that causes
excessive mucus
to be produced
3) Insert the
genetic material
that stops cells
producing excess
mucus
4) The virus
then works
on the cells
in the lung
Gene therapy often involves gametes – why is this controversial?
B3h Cloning
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Dolly the sheep
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My name is Dolly and I was born in
1997. I made history as I was the
first mammal clone. In other
words, I was a geneticallyidentical copy of my parent.
Of course, clones have been around for
many years as identical twins are
basically clones:
Cloning Animals
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Here’s how Dolly the sheep was cloned:
Host mother
Clone
Applications of Cloning
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1) Animal organ donors – animal organs could be potentially
cloned and modified so that they can be used in humans.
2) Human cloning – cloning can be used to provide stem cells
but these could be used to clone a human.
3) Animals with desirable characteristics could be cloned.
Cloning
Should cloning
be allowed?
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Cloning Plants
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Plants can reproduce ASEXUALLY. The offspring are
genetically ________ to the parent plant and are called
_________. Two examples:
1) This spider plant has grown a rooting
side branch (“stolon”) which will
eventually become __________.
2) A gardener has taken cuttings of
this plant (which probably has good
characteristics) and is growing them
in a ____ atmosphere until the
____ develop.
Words – clones, damp, independent, roots, identical
Cloning Plants by tissue culture
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1) Scrape of a
few cells from
the desired plant
2) Place the scrapings
in hormones and
nutrients
3) 2 weeks later
you should have
lots of genetically
identical plants