- Hello, my lovely kittens.
In this video, we're gonna be covering
all the knowledge that you need
for your first Edexcel biology exam.
Just a quick summary.
So if you wanna make sure
you don't miss anything else,
you can get the free revision
guide over on my website
which has loads and loads of
knowledge checklist, keywords
because there are a lot
of those in biology.
Crosswords for you to fill in
and loads and loads of
pictures for you to fill in.
Thousands of questions
and student friendly
specification statements
with links to videos
to help you out if you don't understand.
Good luck guys.
If there's anything you
need, just let me know below.
(light happy music)
Here, we have our beautiful
plant cell with a cell membrane.
That's responsible for determining
which bits go to in or out of the cell.
And cell wall, important for structure.
The vacuole, important for structure.
The cytoplasm where most
a reactions take place.
The tiny little dots are the ribosomes
which are responsible
for protein synthesis.
The green bits are the chloroplasts.
The pink ones are the mitochondria
where energy is produced
and then last but not least,
we have our nucleus.
Here, we have our animal
cell with our cell membrane.
Again, controlling what goes
in and out our mitochondria.
Where energy is produced, ribosomes.
Which are sort of protein synthesis.
Cytoplasm where most
the reactions take place
and our nucleus, that's
where the DNA is hold
and that's a control center of the cell.
You'll notice there are several features
of a plant cell that
animal cell doesn't share.
For example, the cell wall,
the vacuole, the chloroplasts.
If you wanna copy these pictures yourself,
you can download then
the free revision guide
from my website.
Here we have our bacterial cell
which has its cell membrane
controlling what goes
in and out the cytoplasm
where most of the reactions take place.
The chromosome, the DNA not in a nucleus.
The flagella which is used for locomotion.
Ribosomes for protein synthesis
and then on the outside,
you have the cell wall.
Even though you have
to learn the structure
of a typical plant cell
or a typical animal cell,
there isn't really a typical type of cell
because there are a wide range
of differentiated specialized cells.
We can see here in our cross-section leaf,
it has lots of different
types of cells in.
Here we have a neuron
which looks very different
to a muscle cell which is
going to look very different
to a skin cell or very different
to a set of cells in the gut.
They're going to
specialize to do their jobs
so here we have villi which
give us a long surface area.
Here, the cells are very
tall to provide structure.
Here, the cells have a very long body
so that the neurons can
travel a long distance
and the muscle cells are
going to stretch and contract.
All cells starts off looking at the same
so they have your basic cell structure
and then various different genes
will be turned on and turned off,
and that's when it will
start to specialize.
That's when differentiation
will take place
and it'll grow this
really, really long axon
or a grow the villi or it
will turn into a leaf cell.
Microscope techniques have
varied wildly over the time.
From the very, very basic
starts where you had your lenses
and you had to use the focus
to see what was going on.
These are all generally
hand done, very, very basics
to ones that you're probably
more familiar with in school
would have slightly more
sophisticated lenses
to the massive ones
that I used to work on,
electron microscopes
where they're all controlled by computer.
If you want to work out image
heights, objects heights
of magnification from an image
you've taken from microscope,
the calculation is the
magnification equals image height
over object heights.
We've heard of meters
which are incredibly long.
You're probably between
one and two meters tall.
And we can have smaller
parts of the meter.
For example, a centimeter on
my screen is about that big.
And that is one times 10
to the minus 2 meters.
A millimeter is even smaller.
That's one times 10 to the minus 3 meters.
A micrometer is one times
10 to the minus 6 meters.
A nanometer is one times
10 to the minus 9 meters.
And picometer is one times
10 to the minus 12 meters.
So if our meter is going to
be m, our centimeter is cm,
our millimeter is mm,
our micrometer is a Mu M.
Nanometer, nm and picometer, pm.
As you can see, measuring very,
very small things in meters
wouldn't be a very useful
way of measuring them.
Amylase, protease and
lipase are all enzymes
and work with the lock and key mechanism.
We have our enzyme which has
a very specifically shaped
active sites.
It's only one substrate
or a couple of substrates
are going to fit in there.
The ones that have the
complementary sites.
They're gonna form an
enzyme substrate complex
and then the enzyme is either
going to break apart things
or is going to join together things.
It is then going to release the products
and then the enzyme is
unchanged and can be used again.
You need to know how in
temperature affects enzyme activity
and it is this kind of lopsided curve.
When we have really,
really low temperatures,
there is not enough energy.
At the peak, this is
the optimal temperature.
And then after the peak,
that enzymes get denatured
which means the links between them
holding everything together
are being destroyed.
The enzyme is not killed.
I know the temptation is to say this
but the correct term is denatured.
Our curve for pH is much more symmetrical.
We still have an optimal pH.
But when it is too high or too low,
the bombs aren't going to be in place.
So the active site of the enzyme
is going to break them down.
So again, it's going to be denatured.
There are only a certain number
of active sites on an enzyme
so once they are full up,
the enzyme activity can't keep increasing.
So while they are filling up,
the enzyme activity will increase
the substrate concentration.
But when they are fill up,
increasing substrate concentration
won't increase enzyme
activity any further.
An enzyme can be used as
catalyst for a rate of reaction.
What we will see is the
reaction will start,
it's happen much faster but it
will end up at the same point
the reaction will probably end faster.
This is because there going
to be other limiting factors
like enzyme concentration,
substrate concentration
or reactor concentration.
There are a number of different enzymes
in the digestive system that
you need to be aware of.
Lipase breaks down fats
into fatty acids and glycerol.
It is made in the pancreas
and small intestine.
And works in the small intestine.
Protease breaks down
proteins into amino acids.
It is made in the stomach,
pancreas and small intestine.
And works in the stomach
and small intestine.
Amylase breaks down starch into sugars.
It is made in the salivary glands,
pancreas and small intestine.
And it works in the mouth
and small intestine.
When we're talking about diffusion,
we are talking about things
moving from a high concentration
down the diffusion gradient to
an area of low concentration.
This could be things moving
from an area inside a cell
where they've been made to another area
or it could be things
moving out of a cell.
For example, it could be
happening in the lungs.
These the alveoli, the air spaces
and this is the capillary
traveling around it.
These very, very thin
walls only one cell thick
and carbon dioxide is going
to diffuse from the blood
into lungs so they can be breathed out
and oxygen is going to
diffuse from the lungs
in to the blood so you can
we take it around the body.
All this can be in the guts.
These are the villi of the guts.
This is the gut cavity
here and you notice again,
they are one cell thick.
And just like the alveoli,
have very large surface area.
We going to get digested food
moving from the gut cavity
into the blood so they can be taken around
the rest of the body.
So diffusion is the movement
of gases or any particles
that dissolved in solution moving down
a concentration gradient
from high concentration
to an area of low concentration.
Osmosis is specifically
the movement of water
through a partially permeable membrane
from the area of high water concentration
to an area of low water concentration.
It's you need a partially
permeable membrane.
The pores in it aren't
large enough for the solute
to move through so the
water is going to be the one
that moves through here.
This sort of thing can
happen in root hair cells
where looking at the uptake of water.
Active transport, again, is
a movement across a membrane
but it's from, this
time, a low concentration
to a high concentration against
the concentration gradient.
So our channel or active transport channel
is going to pick up
something that it wants.
It is in there to move
that through the channel
to the other side.
This could happen, for example,
when we're talking about
glucose in the guts
or minerals in ribs.
You are doing such fantastic work.
Well done for making this far
which is gonna take
another little mind pause,
another little break for
you to gather yourself,
refresh yourself and then
we're gonna start again.
Cancer is when cells begin
to divide uncontrollably.
This is going to lead to lumps
which for most people, some
people is the first sign
that something is wrong.
And these lumps can be
divided into two groups.
Benign tumors and malignant tumors.
Benign tumors are slow and
are generally harmless.
Things like warts or
moles are benign tumors.
And having a lump on your skin
generally doesn't do you much damage.
The problem is when they
are malignant tumors.
These are fast growing,
they are aggressive
and they're mobile.
So I don't mean the warts on your arm
or the mole on your arm is gonna get up
and stop moving around.
I mean cells are gonna
move throughout your body.
Cells from the initial lump
are gonna jump into the
bloodstream, move somewhere else
and they could set up tumors,
lumps in other places.
And while a lump on your skin
generally won't do you much damage,
a lump in your brain, a lump in your liver
or a lump in your lungs can
do quite a lot of damage.
There are risk factors involved in cancer
and there are a lot of things
that we have in control of.
Smoking has large
implications in lung cancer.
Diets, a good diets can reduce
your risk of bowel cancer
whereas if you don't eat
much fruit and vegetables,
then you are putting
about in risk of cancer.
The amount of time you spend in the sun
can affect your
susceptibility to skin cancer.
And unprotected sex
can leave your risk of cervical cancer.
Stem cells are fantastic things
because they are things
that have the potential
to turn into any other type of cell.
They have a number of different uses.
For example, if you're
teaching Parkinson's disease,
they can be used to grow new brain cells.
If we talk about brain or
spinal injury, bone injuries,
then they can be used to grow
new bones to fill the gap.
Or if we have organ failure,
we can grow new organs
or parts of organs instead of waiting
and making us wait on the incredibly long
transplant waiting list.
If we want to make stem
cells, then we take a nuclei
out of an egg cell.
We take nuclei from the patient cell
and insert that into the empty egg.
The egg can then start to
develop into an embryo.
From this embryo, the
stem cell are then removed
and stem cells are turned into new cells.
This does come with quite
a lot of controversy
because human embryos
are going to be created
and then destroyed.
And there were lots of
religious objections to this.
People are saying that life
starts with embryos are created
and people object to the
destruction of embryos.
Nervous system is incredibly complex
and is overlaid on our
spinal and muscular system.
It consists of the brain,
spinal cord,
which together are going to make
the central nervous system or CNS.
And all the neurons, the
receptors and effectors.
When you pick up stimuli,
that signal needs to travel
from where you picked up
so your fingers all the way
up to your nervous system,
your central nervous system.
Sometimes, just stopping
at your spinal cord
and then coming straight back again.
That is going to be a reflex.
This is gonna happen when
you touch something hot
and you move your hand away
without even thinking about it.
Other times, something is going to happen.
The signal grabs your
brain you'll think about it
and then you'll decide to move.
The nerve cells involved
in this are really long.
So this cell body here is incredibly long.
And this can send a fast
electrical signal.
However, when we come
to transfer the signal
from one nerve cell to another nerve cell,
things slow down a bit because
they have to cross a synapse.
This is going to be a slow
chemical signal.
As the chemical has to be
released, diffused across channel
and then be picked up and then initiate
another electrical signal.
The advantages of sexual reproduction
is that you'll get are
genetically diverse population,
which means that they're
going to be better protected
from diseases.
The counter to that is a disadvantage
of asexual reproduction is
that you're going to get
a genetically identical population.
So that if a disease comes along
and one plant is susceptible,
that's the all plants,
the whole population or animals
are going to be susceptible
and they're all going
to be wiped out at once.
An advantage of asexual reproduction
is that there is only one parent
meaning that the plant or animal
doesn't have to wait around
for a mate to turn up,
whereas with sexual
reproduction, a mate is required.
And sometimes this can
be quite hard to find
especially in sparsely
populated locations.
Another advantage of asexual reproduction
is that their energy is conserved.
And what I mean by that is that the parent
is putting all of its energy
into conserving its own genes.
So this is like the selfish gene.
It wants its genes, its
genetics to be continued
as opposed to continuing putting energy
into something that only
has half or its genes.
In mitosis, we go from one parent cell
to two identical daughter cells.
The first thing that needs to happen
is that the DNA in the
nucleus needs to condense
into chromosomes and
then they need to line up
down the middle.
Once they're all lined up down the middle
and all the checks are
taking place to make sure
that chromosomes aren't
going to go astray,
they can start to be pulled
apart to either end of the cell.
New nuclei will form and
then they'll separate
into two identical daughter cells.
In meiosis, we are going
to have two divisions.
So our chromosomes will line up,
they will sort themselves down the middle,
there will be a little bit
of crossing over going on.
So they will swap chunks
of their chromosome
to increase the genetic diversity.
They will divide into two
then they will line up
and divide into two again.
And you'll notice that each of the cells
have half the number of
DNA as the parent cell.
Mitosis will lead to two
identical daughter cells.
Whereas meiosis will lead to
four different daughter cells.
You can remember mitosis goes to two
because it have the T in it.
Mitosis is these things
like growth or repair.
Whereas meiosis is used
for sexual reproduction.
So these are going to be gametes.
In mitosis, we are going to
end up with diploid cells
and in meiosis, we are going
to end up with haploid cells.
Haploid cells having
half their number of DNA
as the original cell.
In women, the gametes are eggs and in men,
the gametes are sperm.
In a plant, we have eggs still.
And that is in the stigma.
And then the male gametes
in plants are pollen
and that is on the stamen.
DNA is, I think, surprisingly
easy to get you're hands on.
You have done this in class using DNA,
getting DNA out of fruit or peas
is a really, really common one.
First thing you need to do is mash up.
I'm gonna say peas just because
that's why I got pictures
but it's basically
whatever you're testing.
Add salt water.
Add detergents.
Leave it for 15 minutes at 60 degrees C.
Filter it.
Add iced ethanol.
And the DNA should float to the top
and it will look like white stringy,
like you've put cotton wool in water.
DNA is made from the different
bases that fit together.
So we are always going to
have A connecting to T.
We're always going to
have C connecting to G.
This is always, always,
always going to be the case.
It has a sugar phosphate backbone
and there were two of those which stretch
all away around the outside.
There are two of those.
It is a double helix.
You see that the green is
always connected to the yellow,
A to T, C to G.
The blue is always connected to the orange
and it's going around in a helical
or a double helical structure.
DNA is a long strand of
deoxyribonucleic acid,
made of lots of letters.
As, Ts, Cs and Gs and these twists round
into a double helix.
This double helix is
still ridiculously long
so it's further twists around
so their in a chromosome.
And this chromosome is located
in at the nucleus of a cell.
Gene is a stretch of DNA.
The codes for a characteristic.
Genome is all the genes in a body.
All of the genes that you have.
A gamete is going to be a sex cell.
So in the humans, that
is a sperm or the egg.
Chromosome is bundled up DNA.
Alleles are different versions of genes.
Dominant means you'll need one gene
to express characteristic.
Recessive means you need two
identical recessive genes
to express characteristic.
Homozygous means genes are the same.
Heterozygous means your
genes are different.
Genotype is what genes you have.
Phenotype is the collection
of characteristics
that you have.
We can work out the chances of a disease
or a phenotype being passed
on by doing a genetic cross.
These are the things that
I think should be laid out
very formally and very populate.
So mother's genotype, big R, little R.
Mother's phenotype is carrier.
Father's phenotype, big R, little R.
Father's phenotype, the carrier.
Mother's gametes, Rr, Rr.
Now we can move some
mothers gametes over, R, r.
And the father's down here, R, r.
And then fill in these ones
down and these ones across.
So the mother, R, R.
Then this one down, r, r.
The father, this one across.
R, R, and then for
father, this one across.
r, r.
Then the offspring are going
to have dominant, dominant.
So they're going to be
homozygous, they are non-suffer.
Two of the potential offspring
or half the potential offspring
are going to be
heterozygous and the carrier
and then out of the
offspring, one in four of them
has chance of being a
double homozygous recessive
and being a sufferer.
Polydactyly is a
condition where the people
get one, two, three, four, five, six
little adorable baby fingers.
And it is dominant.
So here, we have a mother who
has two homozygous recessive
and five fingers and a father,
he has a dominant and
recessive and has six fingers.
We can fill in the genetic cross.
Mother, mother, mother.
Father, father, father, father.
And we can see somebody he
has these dominant disease
if they have one gene, they'll pass it on
and that offspring has a 50% chance
of also having polydactyly.
Cystic fibrosis is a recessive disease.
So as we saw in the first example,
if we have two parents that are carriers,
there is a one in four
chance of an offspring
having the disease.
If only one parent is a carrier,
then the chance of the
baby having cystic fibrosis
are virtually nothing
apart from for any mutation
and chances of them
being a carrier are 50%.
Your chromosomes are in the
nucleus and you have 23 pairs.
So that is 46 in total.
I say 23 pairs because
you're going to get one copy
from the mother on one
copy from your father.
So you'll have tow cups of chromosome one,
two cups of chromosome two,
two cups of chromosome three,
two cups of chromosome four.
One from your mother and
one from your father.
This will allow for you to
be homozygous or heterozygous
or dominant or recessive genes.
If you have inherited two X chromosomes,
you're going to be genetically female.
If you have inherited
an X and a Y chromosome,
you're gonna be genetically male.
Genetics will determine your blood group
and in blood groups, A
and B of both dominant.
Whereas O is recessive.
So if your blood group is A,
you are either going to
have two dominant A genes
or you're going to have dominant A gene
and a recessive O gene.
If your blood group is B,
those either going to
be two dominant B genes
or a dominant B gene
and a recessive O gene.
If your blood group is AB,
you're going to have the dominant A gene
and a dominant B gene.
Whereas your blood group is O,
you're going to have
two recessive O genes.
To make this further complicated,
there are also positive and negatives.
It is important that you
know your blood group
and blood group is really
easy to work out in hospital
so that we can determine,
the doctors can determine
what bloody you can receive.
People with an A blood group
can receive from A or O.
People with B blood group
can receive from people
who are B or O.
People who are AB can receive
from A donors, B donors
AB donors or O downers and
people that are blood group O
can receive only blood group O.
If you know a pair of identical twins,
you know that they are
not exactly the same
even though their genotypes are the same.
While they have identical
genes, their phenotypes,
their characteristics and how they look
are going to be very different.
Because your phenotype is influenced
by lots of different things.
Firstly, your genotype.
So that's your DNA,
your genetic information
and your environment.
This is going to lead to natural
variation in a population.
Things are going to lead to
variation in a population
are going to be influences like diet,
exercise and personal choice.
The aim of Human Genome Project
was to determinate sequence of
base pairs in a human genome.
That's a lot of work
because there's roughly
three billion pairs.
They want you to find all the genes
and they wanted to develop faster ways
of sequencing in the future.
The first time it was done, it
took an incredibly long time
and cost a large amounts of money
and it was finished in 2001.
But they did a really good
job of finding faster ways
to sequence in the future.
It is now not as big a job.
It's still quite a lot of work
but it costs roughly 500 pounds
to get someone's genome sequenced.
And this is paving the
way for large advances,
very fast advances in
personalized medicine.
So that if you develop
something awful like cancer
or another genetic disease,
they can tailor the treatment
that they give you exactly
to what your genome needs.
We are at half way through.
Well done, guys.
We can keep going, we can do this.
I do wanna say thank you to a
few people who supported me,
helped me to add captions the video,
captions will make your
vision so much easier.
Beth, Hannah and Nicola,
been fantastic in their support
and Narinder and Izzy are
awesome, awesome teachers
who are supporting me as well.
making new copies of
cells involves copying DNA
over and over again.
And if you try copying something down,
thousands, millions of times,
eventually they'll become a mistake.
And this mistake might happen once
and then get forgotten or
this mistake might be copied
over and over and over again.
And if it gets copied over and over again,
we've got a mutation and
we've got a natural selection.
All of these changes added together
these small changes, these big changes.
This is our theory of natural
selection of evolution,
of gradual change happening over time.
This theory thought up by Charles Darwin.
That means we are more
suited to our environments.
Darwin's theory is that life,
all life that we know
these days has evolved
over the past three billion
years from the first life,
they're very, very simple
unicellular organisms.
That's what in that slushee puddle.
And the way this evolution
happens is via natural selection.
So that random mutations in genes
leads some natural
variation in a population.
So that can be small things
like different hair color,
different eye color or big
things like how tall people are.
So for giraffes being tall
is quite an important thing.
It means they have access to a
larger range of food sources.
An individual's characteristics
which make them better
suited to the environment
are more likely to survive and reproduce.
Whether this is tall giraffes
or finches with different,
say beaks or moths that have
gone black or gone white.
And the genes, these useful,
these desirable characteristics
will be passed on to the next generation.
Evidence for evolution comes from fossils.
Not everything in these fossils
because fossils come
form of the hard parts.
The bones, the soft bits are
just going to decay away.
So it won't leave the fossils.
And we can see evolution
happening with bacteria
because they multiply very quickly,
20 minutes in some circumstances.
So we can see changes,
adaptations for natural selection
being passed on and
happening very, very quickly.
Fossils can show us
changes that have happened.
And how different animals are related.
From these, we can use or
draw an evolutionary tree
showing us how closely
things are related to things
and one one branch in
will be closely related
and the point where they branch off,
that's where they became
genetically distinct.
Activity divide very, very rapidly.
Bacteria is happy, has lots
of feed, has lots of space
and nutrients is going to
divide roughly every 20 minutes.
This allows single mutation to
spread through the population
really quickly.
This is gonna rule out
antibiotic resistance
really easily develop and spread
due to brand new mutations
but those brand new mutations
mean that the bacteria don't
get killed by antibiotics,
they're going to selected
by natural selection.
And bacteria easily passed
from person to person
or from an animal to person
or from an animal to animal
which means antibiotic resistant bacteria
is going to spread it really easily.
Penicillin has saved
many millions of lives,
probably yours at some
point, definitely mine
because before penicillin,
before the widespread use of antibiotics,
people died from very, very common things.
Going into hospital to
have a simple operation,
most of the time was lethal
before the widespread use of antibiotics.
The smallest infection could kill you.
MRSA is a bacteria that is
resistant to most antibiotics.
Now, this happens on your skin,
it's there on your skin all the time.
If you go into hospital
to have an operation,
you'll get swabbed for it
to find out if you have it.
But if you do have it then
you get an infection with it,
there are very few antibiotics
they can use to treat it.
The development of new
antibiotics is very slow,
partly because we've
looked for all of these
in a lot of places and partly
because developing new drugs
is very, very expensive.
So companies are gonna spend their time,
spend their effort and their resources
looking at drugs that are gonna
make them a lots of money.
Drugs that people have to take every day
for heart disease or diabetes.
Antibiotics, you take
once for maybe seven days
and then you don't need them again.
So they don't necessarily make
the pharmaceutical companies
lots of money but they will
cost lots of money to develop.
Carl Linnaeus developed taxonomy
which is the study of grouping
living things together.
We can see on our evolutionary tree here
that some things are very
closely grouped together
and to get to other things,
you actually have to go
quite a long distance.
He develops naming system
where we have each organism
has a two part Latin name
and this will tell us
how closely related they are.
It's a bit like them having a
first name and a second name,
a genus and then a species.
The genus will be the wide
overarching type of thing
and then the species will
be exactly what thing it is.
With each new development in biology,
with this new development in genetics,
we understand more and
more about classifications
so our taxonomy and our evolutionary tree
is evolving all the time.
The three domain system
divides everything in life
into three groups.
Eukaryotes, bacteria and archaea.
Eukaryotes are things that have nuclei.
I think we can take a second to appreciate
how thoroughly cute these little guys are.
Before we start about serious
issue of selective breeding.
Selective breeding is breeding an animal
for a particular characteristic.
It happens with dogs,
it happens with cows,
with horses, with cats, with chickens,
any animals that we keep and we're looking
for a particular characteristic
have probably undergone
selective breeding.
And the advantages are
is that your animals
which have the desired characteristic.
Whether it's the very flat face of a pug
or horses that run fast or cows
that produce a lot of milk.
It is important commercially
that dairy farmers
have cows that produce a lot milk,
that dog breeders have
dogs that look cute.
However, the disadvantages to this
is if you have a healthy animal
who doesn't display
desired characteristics.
For dairy farmers, they
are looking for cows
that produce a lot of milk.
These obviously going to be female cows.
So any male calf's that are
born, they are healthy animals
but they are not showing
desired characteristic
so they're killed.
Dogs that don't show the
desired characteristic
can be put to sleep even though
they are perfectly healthy animals.
Thousands of dogs, cats
each year are killed
just because they are not cute enough
or do not look like the industry standard.
The desired characteristic can lead
to long term health
problems for their animals.
I've chosen the pug as the example here
because of the large number
of folds on their face,
it squashes their little nose
and it gives them long-term
breathing problems.
Dogs like Labradors are very susceptible
to things like arthritis and
dogs like Rhodesian Ridgebacks,
though desired
characteristic is a mutation.
So any dogs are born without the ridgeback
can be put to sleep.
And then lastly, we have a
lack of genetic diversity
within the population.
So when we're talking about breeding,
this can lead to a lot of inbreeding
where brothers and sisters are bred
to get the desired characteristic
which is going to lead to
recessive bad mutations
coming out more often in the population.
It also means they're going
to be more susceptible
to all the diseases that
are going to be around
because they don't have
the genetic immunity.
We can genetically modify plant DNA
so we can take a DNA without
required characteristic
whether that is a
drought resistant stream.
So there are countries
that don't get much rain
and very, very susceptible to droughts
can survive that better
so their crops are gonna grow better.
Whether that's a gene
which produces a vitamin.
so there are countries that
don't have a good food security,
where food has shortage,
where people are dying
because they're not getting
a wide amount of vitamins,
we can engineer the food,
the rice that they're growing
so that it produces more
vitamins so it's healthier
so that less people are going to die
or whether it's just pesticide resistance
or the ability to resist
being eaten by pests,
being eaten by bugs so that
their yields are higher.
We can take that gene and put
it into our original plant DNA
producing a genetically modified plant.
We can add in the new
gene to the plant DNA,
we can produce seeds and then the farmers
can grow those seeds
and the plants will have this
a new desired characteristic.
Some people don't like
genetically modified plants
because they think it's
interfering with nature.
Genetic engineering has brought around
some fantastic advances.
One of them are useful of this
is the way we produce insulin these days.
Previously, insulin used to
be harvested from pig cells
and that's what people had to inject.
It wasn't very good and
it wasn't very efficient.
These days we've taken
the gene for insulin,
we've taken a bit of bacterial DNA
with the original DNA has
our desired characteristic
and bacterial DNA
reproduces really quickly.
The insertion of the gene for
insulin into the bacterial DNA
means that the bacteria
are now producing insulin.
So we are now producing large
amounts of human insulin
which is a really important
point quickly and safely.
This is much, much better for people
than having to inject pig insulin.
It made things much cheaper,
much faster and much safer.
Health is a complicated concept,
it's going to be your overall state
of physical
and mental well-being.
This is gonna be affected
by a number of things.
It's going to be affected
by your diet, exercise,
community, whether you feel
lonely, whether you have friends
and in part, our genes.
A pathogen is a microorganism
that causes disease.
For example, we can have viruses,
bacteria,
fungi,
and protists.
And this can be spread in
a number of different ways.
They can be spread in the
air, for example, by coughing.
They can be spread by touch,
for example, if you have
bacteria on your hands
or you have bacteria
or virus on your hands
and you touch the table and
someone else then touches
that same table.
They can be spread through
blood, sexual fluids
or they can be transferred by viral vector
like viral mosquito.
Bacteria are going to make you feel ill
because they produce a lot of toxins
so they'll give you things
like food poisoning.
Viruses will make you feel ill
because when they reproduce,
they cause massive cell death.
Cholera is a bacteria.
It is spread generally via water systems.
The implications are severe diarrhea
which is incredibly dangerous
for very young and very old.
So you poor babies.
Pregnant women.
And what they die of is dehydration.
It may sound funny that its
diarrhea but it is deadly.
Tuberculosis is a bacteria
and is spread by coughs and sneezes.
It is going to lead to a cough
which may be bloody.
Fever,
fatigue, swellings, weight
loss, sweats, loss of appetite.
To help combat that, the BCG vaccine
is routinely given to babies and children.
And this can be fatal.
Stomach ulcers were previously thought
to be the result of stressful
living, eating which food,
having too much alcohol.
They were thought to
be a lifestyle disease.
That something that's overweight people
who didn't do enough exercise
and have very, very stressful jobs gots.
And this continued to be the
case until Barry Marshall,
quite a nocuous name there.
Barry Marshall were proved that it wasn't
and he proved that it wasn't
in a rather heroic way.
He thought and he was
right that stomach ulcers
were caused by a bacteria
but nobody believed him
because the idea that stomach
ulcers were caused by stress
and diet was too dominant.
So he drank a solution of the bacteria.
Now, this is an awful, awful, awful, idea
because it's so, so
dangerous and he had no idea
what was going to happen.
But he was so convinced that he was right
and nobody would believe him,
he drank a solution of this bacteria.
He got sick, he waited a while
and discovered he had a stomach ulcer
and then cured it with antibiotics.
And these days, stomach
ulcers are quite easy to cure
with antibiotics whereas previously,
people had to live with the horrific pain
of having an open bleeding
sore in their stomach.
The bacteria, pylori bacteria
is going to be spread
the number ways stomach bugs are spread.
Generally, by pools of sick.
Stomach ulcers are large
open sores in your stomach
so you're going to be vomiting.
Generally, vomiting blood.
It is going to be very painful.
There's going to be
blood in your poo as well
and it is going to be very, very painful.
The damage these days is very little.
Ebola is a virus.
It is going to be spread by bodily fluids.
So vomits, blood, stuff like that.
It is going to lead to diarrhea,
vomiting, rash, pain
and then your liver and your
kidneys gonna stop working.
It is very unpleasant
and highly contagious.
Chlamydia is a bacteria.
It is spread via unprotected sex.
It is one of the most common
sexually transmitted infections in the UK.
About 200,000 people are
tested positive for chlamydia
in England each year and
70% of those are under 25.
The implications are going to be pain
when urinating.
A disgusting skanky
horrible smelly discharge
that is going to come from the penis,
the anus or the vagina.
Bleeding in between periods,
or swollen testicles.
The damage can be long term.
It can lead to infertility.
So the best thing to do
is just wear a condom.
HIV is a virus.
It can be spread in a number of ways.
That is unprotected sex,
sharing needles,
childbirth.
That's from mother to child,
not just general childbirth.
Infected blood,
breastfeeding of formerly infected mother.
The implications are
devastating for someone
although outcomes have
rapidly improved recently
due to the development of new drugs.
So HIV attacks the white blood cells.
White blood cells are an important part
of your immune response.
So if your white blood
cells are being attacked,
then you have a little immune response.
The damage is widespread and HIV
can develop into AIDS where you,
that's acquired immune deficiency response
which can lead to even
the smallest infection
having devastating consequences
because you have no immunity against it.
Malaria is a parasite.
And they're spread by female mosquitoes
drinking your blood at night.
It's not quite as sexy
as I made it out to be.
The implications are
going to be a high fever,
sweats
and also chills.
Headache,
vomiting,
chest and muscle pains
and diarrhea.
And this can be lethal in severe cases.
The body is rather good
at protecting itself
against pathogens.
The stomach is full of
acid which kills bacteria.
Your respiratory system,
your nose, your trachea,
your your bronchi are
full of mucus and hairs
which trap bacteria.
Your skin acts as a barrier
which stops things getting in
and your eyes have tears
which wash them out clean.
Your immune system is brilliantly
clever at protecting you.
It consumes pathogens.
So your white blood cells
will engulf, the will eat anything
that they see as unfamiliar and dangerous
and then it will destroy it.
They produce antitoxins
to counteract the toxins
that the bacteria produce.
And they produce antibodies
so that they can recognize
pathogens faster.
I imagine most of you have been vaccinated
or if you haven't,
at least you've heard about vaccinations.
Vaccinations are given
generally to children
or people that back
that gone on holiday to different places.
And the childhood
vaccination program in the UK
has prevented millions
and millions of deaths
and further millions and
millions of serious illnesses.
In this country, it has
wiped out a large number
of debilitating diseases.
It is very rare to
develop one getting polio
these days in the UK because
we are all vaccinated
against it at a young age.
The polio vaccine isn't too bad
because they give it
to you on a sugar cube
but it is quite painful taking
your eight week old baby
to be injected by the nurse.
A vaccination is gonna
contain small amounts of dead
or inactive pathogens.
This allows your immune
system to develop antibodies.
So if you get infected with
the disease at a later point,
your body already has antibodies to it.
It can recognize it,
it knows its pathogen,
it knows how to deal with and
it can be dealt with quickly
before you get ill.
The advantages are that a
large number of diseases
had been wiped out,
for example, nobody gets smallpox anymore
or polio.
And we have herd immunity
which means if a large
percentage of the population
are vaccinated against disease,
even the small percentage that
decided to not be vaccinated
or can't be vaccinated for medical reasons
are going to be protected as well
because the disease will
find it very hard to spread.
The disadvantages is
they don't always work.
The polio vaccine, smallpox vaccines
are very, very efficient but
things like the flu vaccine
doesn't always work and it can be painful.
And there can be side effects.
You may have heard about controversy
where somebody linked the
MMR vaccine and autism.
This is completely untrue.
There is absolutely no
link between these two.
Because bacteria divides so quickly
and in a good conditions,
they can divide once every 20 minutes,
they're going to be very, very susceptible
to mutations in their DNA.
Completely random changes which
means completely randomly,
one tiny bacteria could
develop the resistance
to an antibiotic.
And it only needs one bacteria
out of a large collection
to become resistant to the antibiotic
for it to become a problem.
Here, we can see an
antibiotic sensitivity test.
These are the discs with antibiotics on it
and you can see the bacteria is growing
all the way up to these discs
but not all the way up to this disc here.
So the role of antibiotics
is to kill bacteria.
Because the bacteria divide
so quickly mutations,
can quickly develop.
If the course of any antibiotics,
any non resistant bacteria
will be killed off and
any resistant bacteria
will survive and grow.
This is natural selection in action
and soon, only resistant
bacteria will be left.
This is a problem because we
are running out of antibiotics
to treat common complications with.
For example, tonsillitis is
easily treated these days,
small infections are
easily treated these days
which previously are more to be lethal.
We use antibiotics far too much.
They're given to animals and
daily, habitually in their feed
and this is driving natural selection,
driving bacteria to mutate.
New drugs need to be
tested for new things.
Toxicity,
efficacy and dose.
Toxicity tells us the level
or the amount of drugs
that we can take before the
side-effects are too bad.
All the drugs that we
take on a daily basis
have side effects.
But since we know how toxic they are,
we know its safe or reasonable
level we can take them out
without suffering too badly
from the side effects.
Efficacy is like how efficient it is.
You can see the similarities
in the two words.
Does it work better or worse
than what's already on the market?
Other side effects, better or worse
than what's already on the market?
Is it worth developing
or taking this drug?
And dose, how much do you need to take
for the drug to be effective.
Epidemiology studies
are going to be looking
at the levels of health and
illness in a population.
We need to do it in a wide population,
so we can look for different risk factors.
For example, we can't force
people, we can't ask people
to eat a high fat diet
or to do lots of exercise
or to drink lots so we can
compare them to other people
who don't do these
things or do those things
but there are people
within a wide population
that do those things already.
So if we wanted to look at the
effect of exercise on health,
we could take our population,
we could look at people
that do lots of exercise and compare them
to people that didn't do any exercise
and because we have such a
large population of people
we're looking at, then we
can compare the two groups.
And we can follow these
groups for years and years
to see what the effects are going to be.
When we have cardiovascular
disease, we have fatty deposits
building up in the coronary arteries,
the arteries around the heart.
This can lead to the
formation of blood clots.
This blood clot can block an artery.
This is going to restrict the oxygen
to some cells.
These cells are going to die.
If too many cells die, this
can then lead to heart attack.
If so many cells die that the
heart can't function properly,
it can't pump blood properly.
Risk factors for this
are going to be smoking,
high blood pressure
or having too much salt
or fat in your diet.
Your BMI is your body mass index.
That is your mass divided
by your height squared.
Well, we use your BMI to work
out whether your underweight,
a healthy weight, overweight,
obese or severely obese.
If you are obese or severely
obese, your are increasing
your risk of type 2 diabetes,
heart disease, some cancers and stroke.
As part of a lifestyle,
some people may choose to
drink alcohol or to smoke.
However, if you drink alcohol,
you are susceptible to you liver damage.
You're increased risk of some cancers,
alcohols lots of calories in it
so you are at risk or being overweight.
Smoking can lead to lung damage
and cancer.
Well done, guys.
Excellent work for making it this far.
The rest is biology only.
So if you're doing combined
science, well done,
you can go and have a relax or
try some quickfire questions
or go through the revision guide.
You need to know how to test
for fats, starch, sugars and proteins.
Fats can be tested for
using the emulsion test
or the filter paper test.
For the emulsion tests you add ethanol.
Shake it.
Add water and look for a color change.
If it goes cloudy, then
lipids are present.
With the filter paper test,
if you rub it on filter paper,
the fills paper should be see through.
To test a starch, you add iodine.
And if starch is present, it
is going to go dark black,
dark blue color.
That means is going to
be a positive result.
To test for additional sugars,
we can add Benedict's solution.
Heat it for two minutes in water bath
and if it goes red, if
there's lots of sugar
or kind of like a pale green yellow
if there's a little bit of sugar.
We'll protein with the biuret test.
So we add.
We add biuret solution
and it will go purple
if it is present.
Calorimetry is testing
how much the temperature of water changes
when we heat it with a
known mass of a fuel.
This can be done with solid fuels.
So we have a known mass of a solid fuel,
you probably have this on a metal skewer
and then you heat the water
most of the temperature change
or it can be done with
a liquid fuel as well.
Here, we have alcohol
in an alcohol burner.
You can then measure
the temperature change
and work out the energy released.
The biggest source for error in this
is going to be heat loss
to the surroundings here
because not all the heat
is going straight up
into heating the water.
The brain is control central of the body.
It makes sure everything's
functions properly
and tells various
different parts what to do.
We have the cerebral cortex,
the cerebellum and the medulla.
The brain is an incredibly
complicated thing to study
because for it to be functioning properly,
it needs me inside a living person.
Doctors can work on mapping
various different things
by using MRI scanning and CT scanning
and giving that person different stimuli
to see which parts of the brain light up.
Here, we have our beautiful
picture of the eye.
Sclera which is the white bit.
The retina which is where
the image is focused.
The optic nerve which
sends message to brain.
The ciliary muscles which
change the shape of the lens.
The cornea which is a protective covering.
Pupil let's light in.
The lens is responsible for focus.
And the suspensory ligaments
hold the lens in place.
If you are short-sighted, you can't see
distant objects and if
you're long sighted,
you can't see close subjects.
In an eye that can see correctly,
the lens will take the light
and will focus the image
on the retina.
Whereas someone that is short sighted,
the image focuses before the retina
and someone that is long sighted,
the image focuses behind the retina.
To correct shortsightedness,
we need a diverging lens.
And to correct long sightedness,
we need a converging lens.
Each three-letter sequence of DNA
is gonna code for amino acid.
So here we have AGA.
We starts off with A,
find G and find the A.
So that DNA sequence is going
to code into the amino acid,
arginine.
The next three along, CTG are
going to code into leucine.
And this will keep going until eventually,
we have a long amino acid chain.
This can then fold up
in very complicated ways
until we get a protein that
will look something like that.
And proteins are responsible
for basically everything
that happens in your body.
They are the hormones,
they are the enzyme,
they're the cell walls,
everything is a protein
or dependent upon a protein.
And these proteins are very, very specific
and enzyme substrates active sites
is going to be very, very
specific to the substrates.
So if there is a mistake
in our amino acid chain,
if something is missing
or if something is wrong,
we put the wrong amino acid in there.
Then, our enzyme, our protein
is going to fold up wrong
what the mutation is going
to have caused a change
in the protein.
Which can then have a massive
impact on how it functions.
Meaning that it might not work properly,
meaning that it might not break down
what it supposed to break down,
meaning they might not
function in the correct way.
There is a massive amount
of DNA in each of our cells
and only some of it is useful.
So say this section
here might be non-coding
which basically means it's like junk DNA
just getting in the way.
There are some phenotypes apart from sets
which are sex linked.
For example hemophilia,
the gene that causes
or would lead to hemophilia
is on the X chromosome.
Whereas females have two X chromosomes
so much more likely to have a
dominant and a recessive gene.
If a male inherits the
recessive gene for hemophilia,
they have no corresponding dominant genes
'cause they only have one X chromosome.
When Darwin proposed
his theory of evolution,
it was very controversial.
There were lots of religious objections.
This is because he was
saying that the Earth
was billions of years old
whereas that's not what
it says in the Bible
and him saying that we
were evolved from monkeys,
or evolved from primordial soup
and that's not what it says in the Bible.
An alternative theory at the time
is the acquired characteristics.
So for example, if you
dyed your hair blonde
during your lifetime
and you had a baby boy,
your hair was blonde, your
baby would have blonde hair.
Wallace worked with Darwin,
they published a paper together
and Wallace was very important
when were talking about speciation
and geography.
Mendel works with sweet
peas and he discovered
or was the precursor to discovering genes
or units of information,
that inherited units of information.
When a single species of animals
gets geographically separated,
and this could be because
there are on different islands
or there could be a
mountain range that pops up
in between them,
then we now end up with a situation
when we have speciation,
where one species leads to
various different species.
And this is called speciation.
Darwin saw this when he was
over in the Galapagos Islands.
The finches, small birds all
started off as one population,
one species but as they
separated out on to the islands,
I dare say the got
separated from each other,
they became quite different.
The main difference was
in the shape and length
of that beaks as they became more adapted
to the food sources on
those different islands.
So they either had to dig
down deep to get the food
or whether the food was on leaves,
whether it was hard to reach,
whether the food was easy to reach.
There is a number of different ways
that cloning can take place.
We can do it with the plants
where we just chop a little bit off,
pop that into something
like rooting hormone,
put it into the soil,
put it into the new pot
and it will grow into a new plant.
This works really well
with things like lavender
or strawberries.
We can do it back to tissue culture,
we'll be having that one cell divide
then we can take that, put
it into further Petri dishes
until we have lots of dishes of the same.
Plant disease can be identified
in a number of different ways.
This could be due to
discoloration of the leaf.
So here, we have the tobacco mosaic virus
where you can see the leaves go uncolored
or there could be a black color developing
as embrace black spots,
the leaves could fall off.
It could have a loss of vigor.
It basically means it falls
over and looks pathetic.
The flowers could develop wrong
or they could not develop
at all or it could die.
However, a poorly looking plant
doesn't necessarily have a disease.
It might have an iron deficiency.
If it has low nitrates, it
is going to have poor growth,
plus yellow leaves.
If there are life phosphates,
it is going to have poor growth
plus discolored leaves.
A low potassium is going
to lead to poor flower
and fruit growth.
And low magnesium is
going to be yellow leaves.
This course is over into chemistry.
This is why your NPK
fertilizers are important.
If you want to produce
an uncontaminated culture of bacteria,
moving your bacteria from
one place to another,
you first need to flame
your inoculation loop
so that it is red hot.
This makes sure it kills
everything that is on there.
You need to make sure
that you open your bottles
near the flame so that
no further contamination
can get in there.
Open the lid as little as possible
flaming the lid as you go.
Work as quickly as possible to transfer
the sample of bacteria
that you've picked up
into your uncontaminated bottle.
And working as quickly as possible
so you don't get any other
bacterial contamination.
You can then leave the
sample at 37 degrees
if you've got incubator or
just leave it on the bench
at 25 degrees and for a few days
and your bacteria will grow.
I've done a much longer
video explaining this
as you can see into here.
If you want to have a look at that,
it's in at the playlist
with all of the other required practicals.
When we are going to be looking
at the effect of antibiotics
or antiseptic on how bacteria grow,
we need to make sure that our work area
and our hands are clean,
because even though these
bacteria are relatively safe,
is we have to assume
they're going to pathogenic.
You need to make sure you've
labeled the underside,
not the lid of the agar plates.
And these plates are probably
already be seeded for you
by the technician.
You can put your little
filter paper discs on there.
Use forceps to do this
and then incubate them
on 25 degrees for 48 hours.
We can then measure the clear zones
in two different directions.
Here, the clear zone
is slightly hard to see
but hopefully, if you look close enough,
you can let's see it.
It's better if you measure the diameter
but in this case, the
only thing like you do
was to measure the radius
because the clear zone was so large.
Here, we have our lovely little mouse
who's going to be vaccinated
and this is what's going to start
the formation of antibodies.
After a while, cells from
the spleen of the mouse
where the antibodies
are form are collected.
We can take a known cell
line or cancerous cell line,
myeloma cells and we
can fuse them together.
After the antibodies
and the cancer cell line
have been fused together,
we end up with a hybrid cell.
These hybrid cells can be grown
in culture in a laboratory
and here, we have lots and lots of them.
After they've grown up,
the cells can be taken
and the cells and the
antibodies can be separated.
The antibodies can then be used
for various different things
like pregnancy tests or cancer detection.
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