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Biological Sciences • 9781398375352
Chemistry • 9781398375383
Physics • 9781398375468
WONDERS OF CHEMISTRY
antibacterial properties and can
cause biofilms to dissolve.
In experiments, fragments of
ageliferin have resensitised
certain antibiotic-resistant bacteria,
making them susceptible
to antibiotics again. There is therefore
the potential to use
ageliferin and related compounds
as antimicrobial agents. To do
this, chemists need efficient ways
to synthesise this complicated
molecule. They can look to nature
for inspiration.
Sponge-inspired
chemistry
Look inside
Learning from nature
Nature can inspire organic
chemists in the synthesis of natural
products for biological testing
and screening. Here we look at
one example from a coral reef
Figure 2 The core of the ageliferin
molecule could be formed
through a cyclisation reaction between
two molecules containing
imidazole rings. Each curly arrow
shows the
electrons to make a new bond. R represents movement of a pair of
part of the molecule
shown in black in Figure 1
h ssurveillance
Animal healtth
The orange elephant ear
sponge (Agelas clathrodes)
lives on tropical coral reefs
EXAM LINKS
Thermal imaging in three stages
used
image of a dairy cow’s head can be
Stage 1 of the project will test if a thermal
it is
This would help to establish whether
to estimate its core body temperature.
possible to tell that a cow has a fever.
to
camera attached above groups of animals
Stage 2 will fly a drone with a thermal
in fields can be established. If we can
see if a ‘normal’ pattern for their distribution
image
may then be possible, using advanced
establish what is normal for a herd, it
, to identify when something is amiss.
learning
machine
including
analysis methods,
be
from its previous position, there might
For example, if an animal has not moved
investigate.
to
needs
something wrong and the farmer
that such data would take through
The final stage aims to map the ‘journey’
farmers and
who would find the data useful, from
different sites, interviewing people
vets to government officials.
Pankaj Agarwal
EXAM LINKS
Biological
Sciences
Review
This ‘Wonders of chemistry’ is relevant
to the following
A-level topics:
curly arrow mechanisms
alkaloids
natural products
medicinal chemistry
Inside
C
the Sun
Optical image of sheep at
pasture at Cochno Farm
and Research Centre,
University of Glasgow
■
■
a positron (e+) and an electron
neutrino (ν ). Each deuterium
e
nucleus exists for only about
1 second before fusing with
another proton to produce the
light isotope of helium (3He)
with gamma radiation (γ). There
are then three possible paths
oral reefs are rich marine ecosystems.
to generate helium (4He). The overall
They are found
result is:
in warm, shallow, tropical seas,
but also in cold, dark
411H + 2e– ➝ 4He + 2ν + 4γ
deep oceans. The reefs are built by
2
e
thousands of species
of coral polyps. These are invertebrate
The ppI chain (Figure 2) accounts
animals that deposit
for about 69% of the Sun’s
calcium carbonate, creating beautiful
hydrogen fusion. The ppII and ppIII
and varied structures,
chains involve other nuclei
Drones
which are home to many species
of fish and other sea creatures
at intermediate steps, but the final
result is the same.
researchers
(see Chemistry Review Vol. 28, No.
To detect diseases like FMD more rapidly,
4, p. 34). The huge variety of
thermal
life in a coral reef leads to a rich
are experimenting with drones and Radiative and convection
chemistry of natural products.
zones
to count and
Some of these exotic marine natural
imaging. Drones are already being used
Thesponges
products show promising Figure 1 Ageliferin
layer
is produced go some
if
surrounding
and tell
further
the core is called the radiative zone.
marine
one step
and has
cattle, so can we by
therapeutic activity.
antimicrobialherd
Here,
properties.
The core
the
of the notices? Currently
energetic
gamma rays bounce around between
(of
interest to
are illinbefore the farmermolecule
chemists), is animals
highlighted
nuclei,
orange
causing
relies on postexcitation, followed by the emission
Sponges
and mouth disease
in the UK, animal health surveillance
Foot
of photons with
laboratory
UK
same, or lower, energy in randomised
of animals andthe
damage to the
examinations
Florida.
mortem
It can
vary in
directions. By this
(FMD) outbreak of 2001 caused huge
Sponges
colour from yellow
disease(mostly
mouth
aquatic
A and
foot andare
to process
faeces).
The
reddish-orange,
tissue,
marine) creatures, It is estimated
(e.g. blood, saliva,
of radiative
simple, toishave
diffusion, energy is gradually transferred
tests on
usually found
livelihoods and animal welfare.with
Pankaj
farmers’
at samples
hollow
Agarwal
depths greater than 10 metres.
industry,
bodies.
explores
agricultural
to farmers,
They
have
a porous structure, FMD is a severe,
The
outwards
sponge
(Box
2). Also in this layer, some of the
system that would provide early warnings
which highly
contains secondary
food sectors roughly £3.1 billion.through
anddeliver
water
loose electrons
metabolites
agricultural
the can
welfare
cost
flow and
animal
that
are
the Sun’s
improve
adults,
distasteful
could
nutrients
debilitates
structure
makers
to
and
predatory
are captured by helium nuclei
directly
animals
and
vets and policy
young to
the cells.
of livestock. It can kill
fish. It is metabolites
(He 2+) to form singly ionised
viral disease
contagious
like these that make
The orange
disease.
with this
elephant ear sponge
disease in the
+
sponge
as an exotic
interesting
helium
It is classed
clathrodes)
(He
the processes
). The radiative zone temperature
lives on to chemists. and reduce costs associated
of fever and sores.(Agelas
within
development
through
is about 5 × 10 6 K.
tropicalthecoral
reefs init the western in the country.
The next layer, 150 000 km below
Pacific and western
that it is not normally presentcentral
meaning
Biochemically, Agelas clathrodes
UK,
the Sun’s surface, is the
Atlantic,
including the CaribbeanFebruary 2001, but in the preceding 2 weeks,
is fascinating.
convection zone.
Among
Bahamas and and
Here, photons from the radiative
FMD was confirmed in the UK on 20 Sea around thewere
it contains ageliferin (Figure 1),
transported other compounds,
zone are
as infected animals
RESOURCES
which
absorbed by
has
atoms
and ions, which raises their temperature.
it had spread undetected to 43 farms
abattoir,
The
Core
www.hoddereducation
discovered among pigs at an Essex
country. Initially
the.co.uk/chemistryreview
Health Datasheet
GLOSSARY
■
■
traded throughout
and
World Organisation for Animal
and even France were already infected
1
The terms in bold link to topics in sheep as far away as Cumbria, DevonThe
1
H
extremely sheep,solar
were
H7
on FMD:
and pigs
the AQA, Edexcel, OCR,
cattle core,
where
the density
spread, 6 milliondense
is around
th-disease
WJEC and CCEA A-level specifications,
the disease. To curb disease
spreading
1.6 × 105 kg m–3, contains about
www.oie.int/en/disease/foot-and-mou
as well as the IB, Pre-U
half the Sun’s total
mass but
and SQA exam specifications.
culled during the course of the outbreak.
takes up only about 1.5% of its
a disease detective:
Become
total volume. Like
HE_ChemR_V32_1_Print.indd
the cloud
In the Sun’s core nuclear fusion
7
le/applications/sto/web-app.
from which it formed, the Sun consists
produces photons that
of mostly www.cdc.gov/mobi
hydrogen and
image ofinsheep
a random walk. The resulting heating
Infrared diffuse
helium, with very small amounts
drives
html
of other elements
convection,
at Cochno Farm
at pasture
EXPLAINED
so hot plasma reaches the
(O, C, Ne,
TERMS
as a ν
solar surface.
N, Fe, Mg, Si and S). The core is a
learning algorithm ‘counting’ cattle
Machine
Centre, between plasma
Interactions
mixture
system
and Research
a
that
of
protons,
idea
neutrons,
based on the
and the Sun’s magnetic field
intelligence,
nuclei
and free electrons.
of Glasgow
drone herds them:
Machine learning A form of artificial
University
produce
sunspots, flares and prominences.
given, then identify patterns and potentially
https://youtu.be/C3uHJhjhLuE
can learn from the data it has been The core is where the Sun’s nuclear
1
reactions take place.
H
2
intervention.
H
Hydrogen
make decisions with minimal human
fuses to make helium,of
Accompanying45explanatory article:
of
and every second
about
3.9 × 10
represents the intensity radiation
atoms that
of hydrogen
(infrared) imaging Imaging
https://tinyurl.com/2mz9778t
undergo nuclear reactions and release
hen we look at the stars inThermal
the night 7–14
a huge
it µm.
is difficult amount of energy, which
wavelengthssky,
Infrared image of a dairy cow’s
head in the barn after milking
at Cochno Farm and Research
Centre, University of Glasgow
eventually escapes as solar radiation.
to imagine that the Sun is also
a star — a gigantic
In the Sun, hydrogen fusion is
ball of superheated plasma (ionised
by a sequence of reactions
gas). It is a called pp chains
γ
(proton-proton chains). The first
main-sequence star, with luminosity,
step is the
LSun, of 3.83 × 1026 W and fusion
of two protons (1H) into deuterium 2
a surface temperature of 5800 K,
( H) by emitting
putting it in spectral class G2
(Box 1). The average lifetime of
a G2 star is about 10 billion
(1010) years, and the Sun is about
9
4.5 × 10 years old.
internal structure:
Around 4.5 billion years ago, gas and
dust in a cold cloud were
•
core
pulled together by gravity, increasing
the density and attracting
• radiative zone
more gas and dust to places where
McManus, School of Veterinary
• convection zone
subsurfaceRosemary
flows
the density was greatest.
The infalling material would
Medicine, University of Glasgow
have accelerated and heated
up. When the pressure in the centre
photosphere
(core) of the collapsing
protostar increased above 2.5 × 1016
Pa and the temperature rose
to 1.5 × 107 K, thermonuclear reactions
started, and our
esreview
Sun spots
Sun
.co.uk/biologicalscienc
prominence
www.hoddereducation
was born.
Box 1
Alkaloid A biologically made nitrogen-containin
Classifying stars
g
organic compound, produced by
a wide range of plants
(and a few animals). Alkaloids are
Stars can be classified according to
basic and form salts
their surface
withtemperature
acids. Many are very poisonous
(deduced from their colour and the
to humans, having
lines in their
spectra) and effects. Examples
pharmacological
their luminosity (radiation output
include caffeine,
power). morphine, cocaine
and atropine (see p. 34).
A Hertzsprung-Russell (HR) diagram
plots luminosity
Biofilmsagainst
Communities of microorganisms
temperature for a large number of
that
stick
stars (Figure
1.1). Many
together
and stars
can also adhere to surfaces.
lie on a diagonal band known as the
main sequence.
Diels–Alder reaction A reaction
Astronomers use letters to indicate
where a conjugated
a star’s spectral class and
diene (containing delocalised electrons)
hence its temperature. The sequence
and an alkene are
runs from hottest to
converted into a cyclohexene derivative
coolest — O, B, A, F, G, K, M — with
(see Chemistry
subdivisions 0–9. Our Sun
Review, Vol. 29, No. 1, pp. 18-21).
is a G2 main-sequence star.
Enzyme A specific type of protein
106
(or protein-based
molecule) that acts as a biological
catalyst; i.e. it
speeds up a chemical reaction in
a living organism whilst
remaining unchanged itself.
supergiants
104
Heteroatom A term used in organic
chemistry to mean
any atom other than carbon or hydrogen.
Intramolecular Relates to something
occurring between
102
parts of a single molecule, rather
than between two
different
giants molecules. For example, the term
can be used in
relation to reactions or forces.
1
8H
1
1
H
main sequence
8
ν
white dwarfs
10–4
1
H
O
2
H
B
A
25 000 10 000
The Sun’s anatomy
Box 2
3
He
3
He
H 21
1
Figure 1 shows the layers that make
up the Sun, deduced from
modelling and calculations based
on observations of the Sun
and its radiation.
chromosphere
corona
Figure 1 The Sun, with its layers
and active regions
Physics Review September 2022
K
M
3000
temperature/K
1
H
Radiative diffusion
In radiative diffusion, photons are
scattered or emitted in
random directions: their journey is
a random walk (Figure 2.1)
The mean free path, λ, is the average
distance a photon travels
before being absorbed or scattered
again. After N steps, the
average displacement, D, for a large
number of photons is:
D=λ N
λ
He
= proton
= neutron
γ = gamma ray
2
G
6000
4
flare
coronal hole
F
Figure 1.1 Stars plotted on an HR
diagram
γ
2022
Biological Sciences Review September
During such a collapse, any small
swirling motion speeds up,
due to conservation of angular momentum.
Consequently, the
Sun now rotates with a period of
about 27 days.
Chemistry Review September 2022
Sun
10–2
HE_ChemR_V32_1_Print.indd
W
20
= positron
ν = neutrino
Figure 2 The ppI chain of reactions
(the two positrons will each
meet an electron and annihilate to
produce a gamma)
D
Figure 2.1 A random walk
www.hoddereducation.co.uk/physicsreview
3
58
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hoddereducation.com
education@hachette.co.uk
Chemistry
Review
luminosity/LSun
it? With
was sick without having to examine
What if we could tell if an animal
are
imaging and machine learning, we
a combination of drones, thermal
faster treatment and interventions
attempting to do exactly that – to enable
Ageliferin belongs to the imidazole-contai
ning alkaloid class
of organic natural products (see
p. 22 and p. 34). The core part
of the molecule, which is supposed
to be responsible for this
mode of activity, is highlighted
in orange in Figure 1. In the
sponge, ageliferin appears to originate
from an enzymatically
catalysed cyclisation reaction
between two molecules that
contain imidazole rings (Figure
2).
Chemists are chiefly interested
in studying the synthesis
of the ageliferin core structure.
This is so that a library of
ageliferin derivatives can be biologically
tested for possible
antimicrobial properties. In nature,
the enzyme holds the
reacting molecules in precisely
the correct orientation to
produce the required product. However,
in the laboratory, this
proposed cyclisation, using a Diels–Alder
reaction between
the two reactants, would be difficult
to achieve.
Instead, chemists have designed
an alternative cyclisation,
using an intramolecular reaction.
This is so that the double
bonds can flex into the correct
position for the new bonds
to form. The reaction is summarised
in Figure 3, although in
reality there are more steps involved.
This is because protecting
groups need to be added to the
starting molecule, in order to
prevent other, unwanted, reactions
occurring.
Physics Review
