Properties of Water and Hydrophobic Effect

Summary

This 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

00:00

🌊 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.

05:01

🔗 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.

10:01

💧 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.

15:04

🤝 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.

Keywords

💡Biochemistry

Biochemistry is the scientific study of the chemical processes and substances that occur within living organisms. It is central to understanding the molecular basis of life and plays a crucial role in the video's theme by providing the context for discussing the chemical properties of water and its interactions with biological molecules and processes.

💡Water as a Solvent

In the context of the video, water being a solvent refers to its ability to dissolve various substances, which is fundamental for many biological reactions. Water's role as the 'universal solvent' is highlighted by its importance in the body's cells, enabling biochemical reactions to take place.

💡Polar Molecule

A polar molecule, such as water, has an uneven distribution of electron density, resulting in a molecule with distinct positive and negative ends or poles. The video explains how water's polarity, with a partial negative charge on the oxygen atom and partial positive charges on the hydrogen atoms, influences its interactions and is key to the hydrophobic effect.

💡Electric Dipole Moment

The electric dipole moment is a measure of the separation of positive and negative electrical charges in a system. The video describes how the bent shape of the water molecule creates an electric dipole moment, pointing to the direction of the molecule's polarity, which is essential for its solvent properties.

💡Hydrogen Bond

Hydrogen bonds are a type of strong intermolecular force that occurs between a hydrogen atom covalently bonded to a highly electronegative atom and a negatively charged atom. The video emphasizes the significance of hydrogen bonds in water's ability to form stable structures and dissolve other polar substances.

💡Hydrophobic Effect

The hydrophobic effect is the phenomenon where nonpolar substances tend to aggregate and exclude water in an aqueous solution. The video explains that this effect is a direct consequence of water's polar nature and its strong intermolecular bonds, leading to the aggregation of nonpolar molecules to minimize the disruption of water's hydrogen bonding network.

💡Nonpolar Molecule

A nonpolar molecule is one where the charge distribution is even, resulting in no separation of positive and negative charges and no electric dipole moment. The video discusses how nonpolar molecules, due to their lack of polarity, do not interact favorably with water and lead to the hydrophobic effect.

💡Biosynthesis of Proteins

The biosynthesis of proteins refers to the process by which cells produce proteins. In the video, this process is mentioned to illustrate how water's properties allow proteins to achieve their final three-dimensional shape, which is critical for their function in the body.

💡Ionic Bond

An ionic bond is a type of chemical bond formed through the electrostatic attraction between oppositely charged ions. The video uses the example of sodium chloride (NaCl) to explain how ionic bonds can be broken in water, leading to the formation of hydrogen bonds with water molecules.

💡Dissociation

Dissociation in chemistry refers to the process where ionic compounds separate into ions when dissolved in a solvent like water. The video explains that the dissociation of polar substances such as sodium chloride in water is facilitated by the formation of hydrogen bonds, which is favorable due to water's polar nature.

💡Intermolecular Bonds

Intermolecular bonds are forces of attraction between molecules. The video highlights the importance of these bonds, especially hydrogen bonds, in the context of water's ability to dissolve substances and the hydrophobic effect, which is influenced by the disruption and formation of these 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