The whole of Edexcel Biology Paper 1 in only 84 minutes!! Revision for 9-1 GCSE Bio Combined Science

– 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. (upbeat light music).

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