Unit 10: Biological
Molecules and
Metabolic Pathways
A: Understand the structure and function of biological
molecules and their importance in maintaining
biochemical processes
Pearson BTEC Level 3 National Extended Diploma in
Applied Science
Student: Nikki C. Moslares
,The structure, function and roles of the following biological
molecules in living organisms:
Biological molecules are also known as a biomolecule, these substances are made
by cells and living organisms. Biomolecules has a vast selection of sizes, structures
that has different functions. Most biomolecules share a common fundamental
relationship between function and structure. There are five major types of
biomolecules are water, carbohydrates, lipids, nucleic acids and proteins.
Water – this biomolecule makes up 80% of a cell’s contents. Water always
plays a vital role in the processes of living organisms. Water overarches all
+biomolecules, water is needed for solubility, movement and life. Astrophysicists
typically look for evidences of water when questioning the probability of life on
other planets like Jupiter’s moon, Mars and Titan. There are three different
characteristics of water: solid (ice), liquid (H2O) and gas (steam). The structure
and its biological properties will show how these characteristics can be observed
on water. (Biological importance of water: A-level (A2/AS) biology revision notes 2023)
Structure of Water:
These water molecules are highly polarized molecules which are efficient in
creating extensive branches of hydrogen bonds. Water has a simple molecular
structure, it is made up of two hydrogen atoms that form a covalent bond (sharing
of electrons) with an oxygen atom. Oxygen has a slight negative charge (-) and
hydrogen has a slightly positive charge (+), each covalent bond shares electrons
unevenly - due to oxygen more electronegative than hydrogen. Water displays an
H-O-H angle that has an estimate of 104.5 degrees. The center on each hydrogen
atoms is 0.0957nm from the oxygen atom. (see fig.1) (Bonding - hydrogen bonding in
water (A-level chemistry) 2022)
fig 1
,The molecule portrays an uneven distribution, thus, oxygen gathers negatively
charged electrons towards it, leaving hydrogen with the positive electrons. This
process is due to its electrostatic attraction – where atoms can get attracted or
repulsed. The polarity of water allows
all water molecules to get attracted at
each other, wherein, they stick together
which results to hydrogen bonds where
positive poles of the hydrogen will
bond to the negative poles of oxygen
atoms from a different water molecule.
(see on fig. 2) Hartley, J. (2016)
figure 2 by: USGS
There are three methods for a water molecule to maneuver: Vibration – the H-O
bonds are either stretched or bent. Rotation – the rotating of molecules around its
center of gravity and Translation – to transform from one place to another. This
motion of molecules across space is due to intramolecular and intermolecular
bonds. (fig 3)
fig 3
To differentiate:
Covalent bonds that link hydrogen and oxygen atoms in a water molecule are
known as intramolecular bonds. While the bonds amidst water molecules in ice are
called intermolecular bonds. It is known that intramolecular bonds are 25 times
stronger than intermolecular bonds when binding H2O molecules.
All three ways of water motion interrupts the bonds within water molecules.
When the system gets warmer, thermal energy of water molecules begins to
increase and the molecules will not be able to sustain its rigid structure as ice.
During this stage, the solid melts to a liquid state wherein intermolecular bonds are
continuously broken and reconstructed. In the course of time, thermal energy in
water makes the water molecule to move too fast that intermolecular bonds cannot
happen, then the liquid boils which then forms as a gas. To identify the difference
, between solid, liquid and gas, the strength of their intermolecular bonds is tested
along with thermal energy. At specific temperatures, substances that has strong
intermolecular bonds are characterized to be in a solid state. Intermolecular Forces.
Available at:
https://chemed.chem.purdue.edu/genchem/topicreview/bp/intermol/intermol.html#:~:text=The
%20covalent%20bonds%20between%20the,teams%20from%20the%20same%20institution.) (Accessed:
February 23, 2023).
Properties of water:
High surface tension – as water has ‘’an extensive branches of hydrogen
bonds’, the hydrogen bonds will execute a strong downward force towards
water molecules at their surfaces, resulting in water having a higher surface
tension. In addition, high cohesion makes up high surface tension. Cohesion
is where two similar molecules get attracted and water is a great example
because water is a polar molecule in which water molecules get attracted to
other water molecules. When water is put on a wax paper, the water adheres
weakly to the paper but strongly to itself, the water molecules holds the
droplets in a configuration which produces the least amount of surface area.
This is how high surface tension allow some aquatic insects to stand or walk
on top of water surfaces. (Water - Liquid Awesome: Crash Course Biology #2 2012)
Water - Liquid Awesome: Crash Course Biology #2 (2012) YouTube. YouTube.
Available at: https://www.youtube.com/watch?v=HVT3Y3_gHGg (Accessed: February
23, 2023).
Capillary action - However, there is a limit on the cohesive force of water, in
which, some substances have stronger cohesive forces such as glass, this is
where Adhesion takes place. While cohesion is an attraction of water to
water, adhesion is the attraction of water to other substances. As water has
an uneven distribution of electrons because of the covalent bonding of
hydrogen and oxygen atoms. Adhesion forces are required for water to get
attracted to other substances. This adhesion and cohesion is what makes
plants and trees to thrive through capillary action. Capillary action is vital in
moving water from the roots of plants to its leaves and branches, this is
because of cohesion (water molecules always stick to each other) and
adhesion (water molecules can stick to other substances). Adhesion will
allow water to stay on the vessel’s wall or plant walls that causes an upward
force on the liquid, resulting to a meniscus (fig 4). (Lesson 10: Properties of water)
Molecules and
Metabolic Pathways
A: Understand the structure and function of biological
molecules and their importance in maintaining
biochemical processes
Pearson BTEC Level 3 National Extended Diploma in
Applied Science
Student: Nikki C. Moslares
,The structure, function and roles of the following biological
molecules in living organisms:
Biological molecules are also known as a biomolecule, these substances are made
by cells and living organisms. Biomolecules has a vast selection of sizes, structures
that has different functions. Most biomolecules share a common fundamental
relationship between function and structure. There are five major types of
biomolecules are water, carbohydrates, lipids, nucleic acids and proteins.
Water – this biomolecule makes up 80% of a cell’s contents. Water always
plays a vital role in the processes of living organisms. Water overarches all
+biomolecules, water is needed for solubility, movement and life. Astrophysicists
typically look for evidences of water when questioning the probability of life on
other planets like Jupiter’s moon, Mars and Titan. There are three different
characteristics of water: solid (ice), liquid (H2O) and gas (steam). The structure
and its biological properties will show how these characteristics can be observed
on water. (Biological importance of water: A-level (A2/AS) biology revision notes 2023)
Structure of Water:
These water molecules are highly polarized molecules which are efficient in
creating extensive branches of hydrogen bonds. Water has a simple molecular
structure, it is made up of two hydrogen atoms that form a covalent bond (sharing
of electrons) with an oxygen atom. Oxygen has a slight negative charge (-) and
hydrogen has a slightly positive charge (+), each covalent bond shares electrons
unevenly - due to oxygen more electronegative than hydrogen. Water displays an
H-O-H angle that has an estimate of 104.5 degrees. The center on each hydrogen
atoms is 0.0957nm from the oxygen atom. (see fig.1) (Bonding - hydrogen bonding in
water (A-level chemistry) 2022)
fig 1
,The molecule portrays an uneven distribution, thus, oxygen gathers negatively
charged electrons towards it, leaving hydrogen with the positive electrons. This
process is due to its electrostatic attraction – where atoms can get attracted or
repulsed. The polarity of water allows
all water molecules to get attracted at
each other, wherein, they stick together
which results to hydrogen bonds where
positive poles of the hydrogen will
bond to the negative poles of oxygen
atoms from a different water molecule.
(see on fig. 2) Hartley, J. (2016)
figure 2 by: USGS
There are three methods for a water molecule to maneuver: Vibration – the H-O
bonds are either stretched or bent. Rotation – the rotating of molecules around its
center of gravity and Translation – to transform from one place to another. This
motion of molecules across space is due to intramolecular and intermolecular
bonds. (fig 3)
fig 3
To differentiate:
Covalent bonds that link hydrogen and oxygen atoms in a water molecule are
known as intramolecular bonds. While the bonds amidst water molecules in ice are
called intermolecular bonds. It is known that intramolecular bonds are 25 times
stronger than intermolecular bonds when binding H2O molecules.
All three ways of water motion interrupts the bonds within water molecules.
When the system gets warmer, thermal energy of water molecules begins to
increase and the molecules will not be able to sustain its rigid structure as ice.
During this stage, the solid melts to a liquid state wherein intermolecular bonds are
continuously broken and reconstructed. In the course of time, thermal energy in
water makes the water molecule to move too fast that intermolecular bonds cannot
happen, then the liquid boils which then forms as a gas. To identify the difference
, between solid, liquid and gas, the strength of their intermolecular bonds is tested
along with thermal energy. At specific temperatures, substances that has strong
intermolecular bonds are characterized to be in a solid state. Intermolecular Forces.
Available at:
https://chemed.chem.purdue.edu/genchem/topicreview/bp/intermol/intermol.html#:~:text=The
%20covalent%20bonds%20between%20the,teams%20from%20the%20same%20institution.) (Accessed:
February 23, 2023).
Properties of water:
High surface tension – as water has ‘’an extensive branches of hydrogen
bonds’, the hydrogen bonds will execute a strong downward force towards
water molecules at their surfaces, resulting in water having a higher surface
tension. In addition, high cohesion makes up high surface tension. Cohesion
is where two similar molecules get attracted and water is a great example
because water is a polar molecule in which water molecules get attracted to
other water molecules. When water is put on a wax paper, the water adheres
weakly to the paper but strongly to itself, the water molecules holds the
droplets in a configuration which produces the least amount of surface area.
This is how high surface tension allow some aquatic insects to stand or walk
on top of water surfaces. (Water - Liquid Awesome: Crash Course Biology #2 2012)
Water - Liquid Awesome: Crash Course Biology #2 (2012) YouTube. YouTube.
Available at: https://www.youtube.com/watch?v=HVT3Y3_gHGg (Accessed: February
23, 2023).
Capillary action - However, there is a limit on the cohesive force of water, in
which, some substances have stronger cohesive forces such as glass, this is
where Adhesion takes place. While cohesion is an attraction of water to
water, adhesion is the attraction of water to other substances. As water has
an uneven distribution of electrons because of the covalent bonding of
hydrogen and oxygen atoms. Adhesion forces are required for water to get
attracted to other substances. This adhesion and cohesion is what makes
plants and trees to thrive through capillary action. Capillary action is vital in
moving water from the roots of plants to its leaves and branches, this is
because of cohesion (water molecules always stick to each other) and
adhesion (water molecules can stick to other substances). Adhesion will
allow water to stay on the vessel’s wall or plant walls that causes an upward
force on the liquid, resulting to a meniscus (fig 4). (Lesson 10: Properties of water)
