Properties of Water and Hydrophobic Effect
Summary
TLDRThis script delves into the fundamental properties of water that make it the quintessential solvent for biological reactions. It highlights water's polarity, creating an electric dipole moment, and its ability to form hydrogen bonds, which are crucial for the hydrophobic effect. The hydrophobic effect, a result of water's polar nature and strong intermolecular bonds, is illustrated through the aggregation of non-polar molecules in water, minimizing the disruption of hydrogen bonding among water molecules and thus stabilizing the system.
Takeaways
- 🧪 Biochemistry is the study of chemical processes in living organisms, focusing on reactions that occur within biological systems.
- 🌊 Water is the universal solvent in biological systems, facilitating a wide range of biochemical reactions due to its unique properties.
- 🔍 Water's polarity, with its bent shape and unequal distribution of electron density, results in an electric dipole moment, giving it a partial negative charge on the oxygen and partial positive charges on the hydrogens.
- 🤝 Water molecules form strong intermolecular bonds, particularly hydrogen bonds, due to the attraction between the partial charges of different water molecules.
- 💧 The small size of hydrogen atoms allows them to form very close and strong hydrogen bonds with oxygen atoms of other water molecules, enhancing the stability of the system.
- 🚫 Non-polar molecules, lacking an electric dipole moment, do not interact favorably with water and disrupt the hydrogen bonding network.
- 📦 When non-polar molecules are introduced into water, water molecules form a 'cage' around them, which is energetically unfavorable as it limits the formation of hydrogen bonds.
- 🤝 In contrast, polar substances dissolve well in water, as their ionic or polar nature allows them to form stabilizing hydrogen bonds with water molecules.
- 🔒 The hydrophobic effect occurs when non-polar molecules aggregate in water, reducing the number of water molecules trapped around them and allowing more hydrogen bonds to form between water molecules.
- 🌡 The hydrophobic effect is crucial in biochemistry, influencing the structure and function of biological molecules, including the three-dimensional shape of proteins.
- 🔬 Understanding the hydrophobic effect is key to explaining phenomena such as protein folding and the behavior of lipids in cell membranes.
Q & A
What is biochemistry?
-Biochemistry is the study of the chemistry of biological reactions and processes that occur in nature, focusing on how these reactions take place within the context of living organisms.
Why is water considered the universal solvent for biological reactions?
-Water is the universal solvent for biological reactions because it allows these reactions to occur due to its unique properties, such as being polar and able to form hydrogen bonds, which facilitate the interactions necessary for biochemical processes.
What property of water makes it a polar molecule?
-Water is a polar molecule due to its bent shape and the unequal distribution of electron density, with oxygen having a partial negative charge and the hydrogen atoms having a partial positive charge.
What is an electric dipole moment, and how does it relate to water molecules?
-An electric dipole moment is the measure of the separation of charge in a system. In water molecules, it is the result of the separation of partial positive and negative charges, pointing in opposite directions due to the molecule's polar nature.
How do water molecules interact with each other due to their polarity?
-Water molecules interact with each other through hydrogen bonding, a strong intermolecular bond that occurs due to the attraction between the partially positive hydrogen atoms of one water molecule and the partially negative oxygen atom of another.
Why are hydrogen bonds considered strong intermolecular interactions?
-Hydrogen bonds are strong intermolecular interactions because of the small size of the hydrogen atom, which allows it to get very close to the oxygen atom of another molecule, resulting in a large electrostatic force over a short distance.
What is the hydrophobic effect, and how does it relate to water's properties?
-The hydrophobic effect is the tendency of non-polar molecules to aggregate in a polar solvent like water, which is a result of water's polar nature and its ability to form hydrogen bonds. This effect occurs because the water molecules form a cage around non-polar molecules, which is not favorable, and the aggregation of non-polar molecules reduces the number of trapped water molecules.
How does the hydrophobic effect influence the structure of biological molecules?
-The hydrophobic effect influences the structure of biological molecules by causing non-polar regions to aggregate and exclude water, which can lead to the formation of stable structures such as the hydrophobic core of proteins.
Why can water dissolve polar substances like sodium chloride?
-Water can dissolve polar substances like sodium chloride because of its high polarity and ability to form hydrogen bonds. When sodium chloride is added to water, the ionic bond breaks, and the individual ions form multiple hydrogen bonds with water molecules, which is a favorable reaction.
What happens when a non-polar molecule is placed in water?
-When a non-polar molecule is placed in water, water molecules form a cage around it, trapping the water molecules and limiting their ability to form hydrogen bonds with each other, which is not a favorable effect due to the reduction in stabilizing interactions.
How do non-polar molecules behave when multiple are placed in water?
-When multiple non-polar molecules are placed in water, they tend to aggregate, which is favorable because it reduces the surface area exposed to water and decreases the number of water molecules trapped around them, allowing more water molecules to form stabilizing hydrogen bonds.
Outlines
🌊 The Polar Nature of Water and Its Biochemical Significance
This paragraph delves into the fundamental concept of biochemistry, focusing on the role of water as a polar solvent in biological reactions. Water's polarity arises from its bent molecular structure and the unequal distribution of electron density, leading to a partial negative charge on the oxygen atom and partial positive charges on the hydrogen atoms. This results in an electric dipole moment, a key factor in water's ability to facilitate biochemical processes. The paragraph also introduces the hydrophobic effect, which stems from water's polarity and is essential for understanding protein structure and other biochemical phenomena.
🔗 The Hydrogen Bonding and Its Impact on Solubility
This section explores the second critical property of water: its capacity to form hydrogen bonds with other water molecules and polar substances. The hydrogen bond, a strong intermolecular force, is attributed to the small size of hydrogen atoms, allowing them to approach the oxygen atoms of neighboring water molecules closely, thus enhancing the interaction strength. The paragraph illustrates how water's polarity and hydrogen bonding ability enable it to dissolve ionic compounds like sodium chloride, breaking ionic bonds and forming a multitude of hydrogen bonds in the process, which is energetically favorable.
💧 The Hydrophobic Effect and Non-Polar Molecules in Water
This paragraph examines the behavior of non-polar molecules when introduced into water. Non-polar molecules, lacking an electric dipole moment, do not interact favorably with water, leading to the formation of a 'cage' of water molecules around them, which is energetically unfavorable due to the restriction of hydrogen bonding. However, when two or more non-polar molecules are present, they tend to aggregate, reducing the number of water molecules trapped around them and allowing for more hydrogen bonds to form between water molecules themselves. This aggregation is driven by the hydrophobic effect, a phenomenon that is crucial in various biochemical processes and the structure of cell membranes.
🤝 The Favorable Aggregation of Non-Polar Molecules in Water
The final paragraph emphasizes the hydrophobic effect, which describes the tendency of non-polar molecules to cluster together in a polar solvent like water. This aggregation is energetically favorable as it minimizes the number of water molecules that cannot form hydrogen bonds due to their interaction with the non-polar molecules. The summary highlights the importance of the hydrophobic effect in biochemistry, particularly in the assembly of lipid bilayers and the folding of proteins, where non-polar regions of proteins come together to minimize contact with water, leading to the formation of stable three-dimensional structures.
Mindmap
Keywords
💡Biochemistry
💡Water as a Solvent
💡Polar Molecule
💡Electric Dipole Moment
💡Hydrogen Bond
💡Hydrophobic Effect
💡Nonpolar Molecule
💡Biosynthesis of Proteins
💡Ionic Bond
💡Dissociation
💡Intermolecular Bonds
Highlights
Biochemistry focuses on the chemistry of biological reactions and processes in nature.
Water is the natural solvent for biological reactions due to its unique properties.
Water's ability to dissolve biological molecules is crucial for their structure and function.
Water is a polar molecule with an electric dipole moment, leading to its unique interactions.
The bent shape of the water molecule contributes to its polarity and reactivity.
Oxygen's electronegativity results in a partial negative charge, while hydrogen atoms have a partial positive charge.
Water molecules can form strong intermolecular bonds, particularly hydrogen bonds, due to their polarity.
The small size of hydrogen atoms allows for strong hydrogen bonds, influencing molecular interactions.
The hydrophobic effect is a key concept in biochemistry, arising from water's polar nature.
Polar substances dissolve in water due to the formation of hydrogen bonds.
Sodium chloride dissociates in water, forming multiple hydrogen bonds with water molecules.
Non-polar substances do not interact favorably with water, as they cannot form strong hydrogen bonds.
When non-polar molecules are added to water, water molecules form a cage around them, limiting hydrogen bonding.
Aggregation of non-polar molecules in water is favorable as it releases trapped water molecules and allows more hydrogen bonding.
The hydrophobic effect demonstrates the importance of water's polar nature and its strong intermolecular bonds in biochemistry.
Understanding the hydrophobic effect is crucial for studying protein structures and interactions in an aqueous environment.
The properties of water dictate the pathways and final structures of biological reactions and molecules.
Transcripts
biochemistry is the study of the
chemistry of the many different types of
biological reactions and biological
processes that take place in nature now
the majority of the different types of
biological reactions that exist in
nature for example in our body and so
the cells of our body they exist in
water so water is the natural solvent
it's the solvent that allows all these
different types of biological reactions
to actually take place in the first
place and because of the properties of
water as we'll see in just a moment
we'll see what these properties are the
the fact that water is a solvent allows
those reactions to follow a certain
pathway and water also actually helps
determine what the final structure is of
these biological molecules for example
one biochemical process in our body
inside the cells of our body is the
biosynthesis of
proteins and as a result of the
properties of water that protein is able
to actually obtain its final
threedimensional shape and we'll discuss
that in much more detail in a future
lecture in this lecture we're going to
focus on two important properties of
water and we're going to see how these
two properties lead to an effect known
as the hydrophobic effect so let's begin
by discussing property number one the
fact that water is a polar molecule it
contains an electric dipole moment now a
single water molecule consists of three
individual atoms we have the central
oxygen atom which is a large molecule
and the two tiny H atoms found on the
side now water is not a linear molecule
it has a bent shape and what that means
is these bonds create a certain angle
that is not 180° so notice the bend
shape of the H2O molecule now oxygen is
much more electr netive than either of
these H atoms and because of that oxygen
is able to pull that electron density
away from these two H atoms and because
it is much more likely that the electron
density will be found around the oxygen
than around the H atoms and at any given
moment in time that oxygen atom will
have a partial negative charge and the
two AG atoms will be deficient of the
electron density and so they will have a
partial positive charge now from physics
we know that whenever we have the
separation of two opposite charges
whenever a positive charge is separated
from a negative charge by a certain
distance there will exist an electric
dipole moment as a result of that
separation of charge so what does that
mean about this water molecule here so
basically we have this partial positive
charge that is a certain distance this
distance here away from this partial
negative charge and so from physics we
know there will be an electric dipole
moment that will exist and will point in
the following general direction now
likewise we have a separation of charge
between these two charges and so there
will be an electric dipole moment that
points in this direction so what that
means is we have these two electric
dipole moments that point this way and
if we add up these two vectors then the
net result will be a vector an electric
dipole moment that will Point beginning
here and will point this way as shown by
the following Green Arrow so this green
arrow basically describes the direction
of our net electric dipole moment of
this water molecule so the fact that
water's polar simply means it has an
electric dipole moment and what that
means is there is an unequal an
asymmetric distribution of electron
density and that gives the oxygen a
partial negative charge and these H
atoms a partial positive charge now
let's move on to the second property of
water its ability to basically form
strong intermolecular bonds with other
water molecules and as we'll see in just
a moment with other polar molecules as
well so let's suppose we have several
water molecules that are in close
proximity how exactly will these water
molecules actually Orient themselves
with respect to one another and how will
they interact with one another well as a
result of the fact that water is polar
it will have a partial positive charge
on the oxygen and so we draw the oxygen
with a blue sphere so the blue sphere
basically designates our partially
negative oxygen while these red spheres
designate The partially positive H atoms
and so if we have these 1 2 3 4 five six
water molecules in close proximity they
will Orient themselves with respect to
one another in such a way to basically
maximize the amount of electric
interactions they're actually
electromagnetic but we can say electric
interactions between the different atoms
on different molecules so because these
H atoms have a partially positive charge
they will be attracted to the partially
negative oxygen atoms and so if we look
at these two a uh these two um water
molecules for example this H atom of
this water molecule will'll try to get
as close as possible to this partially
negative oxy atom and this bond is known
as an intermolecular Bond now the
specific type of intermolecular bond in
this case is a hydrogen bond so anytime
we have the H atom bonding with some
type of negative charge that is a
hydrogen bond now what's so special
about a hydrogen bond well a hydrogen
bond is a very strong intermolecular
Bond and that's because of the tiny size
of that o uh of that H atom so remember
H atoms are the smallest types of atoms
in nature the smallest type of nucleus
is the nucleus of an H atom and so what
that means is this H atom because it's
so small it can actually get very close
to that oxygen atom and if it gets very
close the distance decreases and we know
that our electric force is direct ly
proportional or inversely proportional
to the square of the distance between
our two charges and so because the
distance here will be so small if the
distance is small the force will become
large and if the force is large this
interaction is very strong and this type
of interaction between the H atom of one
water molecule and the oxygen atom of
another water molecule is known as a
hydrogen bond so once again water
molecules interact strongly with other
water molecules via electrical forces or
to be more specific electromagnetic
forces now the small size of the
positively charged hydrogen atom of one
molecule for example let's say this
molecule allows it to get very close to
the negatively charged oxygen of another
molecule for example this molecule right
here the small size of this allows it to
get very close to this oxygen and the
small distance basically means we have a
very strong interaction and this type of
strong intermolecular interaction or
intermolecular bond is known as a
hydrogen bond so we see the fact that
water is a polar molecule and because it
consists of these very tiny H atoms we
form these very strong intermolecular
bonds known as hydrogen bonds when uh
when many of these water molecules
actually are found in close proximity
now these two properties lead directly
into something called the hydrophobic
effect so the hydrophobic effect is a
manifestation of these two properties as
we'll see in just a moment and the
hydrophobic effect plays an important
role in the field of biochemistry so
let's suppose we take water molecules
and we place some some type of polar
substance into the water molecule for
example sodium chloride now sodium
chloride is polar because it consists of
an ionic bond and an ionic bond is
basically a bond in which we have an
unequal distribution of charge so one of
the atoms one of the atoms namely the
chloride is more electr negative so it
will have that full negative charge but
the sodium is not very electr negative
and it will give away those electrons
and so it will have a positive charge
and so if we place the sodium chloride
into water that sodium chloride will
separate that ionic bond will break but
many of these hydrogen bonds will form
and that will be a favorable reaction
and so that's exactly why if we take a
polar molecule or a polar substance and
place it into water the water will be
able to dissociate and dissolve that
substance because of these hydrogen
bonds so due to the high polarity of
water and its ability to hydrogen bond
water can readily dissolve other polar
substances for instance by adding sodium
chloride into water we break the ionic
bond between sodium and the chloride and
we form many individual hydrogen bonds
and this is is a very favorable reaction
for example let's say we Form 1 2 3 4
five of these hydrogen bonds between
sodium and water and we form all these
bonds between chloride and water so even
though we break that sodium chloride
Bond we form many of these hydrogen
bonds and that is overall a favorable
reaction so notice that because the
sodium loses that electron it gains a
full positive charge and so all these
oxygen atoms of the water molecules
Orient themselves and align in such a
way so that the oxygen is in close
proximity with the Sodium and if we
examine the chloride because the
chloride gained that electron it took
away from the sodium it has a full
negative charge and so now all the H
atoms will Orient themselves and will
become very close with that chloride and
that will form all these stabilizing
hydrogen bonds now we know that polar
dissolves polar as a result of this but
what happens if we take water and we
place a single non-polar molecule into
that water what exactly will happen then
well non-polar substances basically have
very little or no polarity and what that
means is polar substances uh uh
non-polar substances have a symmetric
distribution of charge and so they will
not show an electric dipole Moment Like
Water does so non-polar substances have
no polarity and do not interact
favorably with water because if they if
they don't have an unequal separation of
charge that means they cannot form these
relatively strong hydren bonds and so if
we take a single non-polar molecule and
we place it into water what will happen
is all these water molecules will
essentially form a cage around the
non-polar molecule and that is not a
stabilizing effect because all these
water molecules will essentially be
fixed they will be trapped around that
non-polar molecule and these water
molecules will not be able to interact
favorably favorably with other water
molecules so what a non-polar substance
is added to water the water molecules
form a cage around that non-polar
molecule as shown in this diagram this
is not a favorable effect because it
limits those water molecules it traps
those water molecules around the
non-polar substance and it limits the
amount of hydrogen bonds that can form
between these water molecules and that
is not a favorable effect now what
happens if instead of taking one
non-polar substance we take two
non-polar molecules and place it into
our water what will happen now well the
same exact thing will happen at first
initially what happens is once we place
the two non-polar molecules into water
those water molecules will form a cage
effect they will become trapped around
the nonpolar substance and that is not a
favorable process so what actually
happens is is these two non-polar
molecules will aggregate they will
essentially combine and form bonds and
the reason for that is when this process
takes place we basically decrease the
number of Trapped molecules found around
the non-polar substance so in this
particular case we have 1 2 3 4 5 6 7 8
9 10 11 12 13 14 15 16 17 18 19 20 2122
so we have 22 of these water molecules
that are trapped around these non-polar
molecules and because they are trapped
they cannot interact via these hydrogen
bonds with other water molecules
but if these two non-polar substances
actually aggregate together they will
decrease the amount of surface area
around this entire molecule and instead
of having these 22 water molecules that
are trapped we only have 1 2 3 4 5 6 7 8
n of these water molecules that will be
trapped and that is a favorable reaction
because we basically decrease the amount
of um we decrease the amount of water
molecules that are trapped and so we
increase the amount of water molecules
that can actually form those hydrogen
bonds that are stabilizing and this
interact between the non-polar molecules
in a polar solvent such as water is
known as a hydrophobic interaction and
this effect is known as the hydrophobic
effect and it is a result of the fact
that water is a polar molecule and it
forms these strong intermolecular bonds
we call hydrogen bonds so once again if
two or more nonpolar molecules are added
into water our solvent the non-polar
molecules will aggregate together and
this is favorable because it releases
those trapped molecules
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