The document discusses the key components and functions of lipids. Lipids are hydrophobic molecules that are rich sources of energy. They are composed of glycerol and fatty acids. Fats are triglycerides formed from glycerol bonded to three fatty acids. Phospholipids are major components of cell membranes that form bilayers in water. Steroids have four fused carbon rings and include cholesterol, important in cell membranes. Lipids store energy, organize cell interiors, and act as hormones. Essential fatty acids must be obtained through diet.

1. The Molecules of Life-
Introduction to the Structure and
Function of Large Biological
Molecules (1)

2. Learning Objectives
• Revise the basic biochemical reactions, elements and type of bonds relevant to
biomolecules
• Enumerate the functional groups present in biomolecules.
• List the difference between monomers and polymers.
• Explain the reactions for synthesis and breakdown of biopolymers
• For each group of biomolecules learn the name of its generic monomer (simple
unit) and polymer (complex structure) and their function.
• Identify the chemical elements and the difference between simple sugars and
complex carbohydrates
• Identify the chemical elements of lipids and learn their property of insolubility in
water.
• Compare and contrast saturated, mono-unsaturated, and poly-unsaturated fatty
acids.

3. Atoms
All matter is
composed of very
small particles called
atoms
Every atom has an
orbiting cloud with
electrons
At the center of an
atom there are the
neutrons and the
protons (in the nucleus)

4. Atoms
• At the center of an atom there are
the neutrons and the protons (in the
nucleus)
• Protons have positive charge (+ve
charge)
• Electrons have a negative charge (-
ve charge)
• Neutrons have neutral charge

5. What is an ION?
• Atoms in which the electrons is not equal to protons is
called an Ion
Cation
1. Have positive charge.
2. Have more protons
than electrons
3. Will move towards
cathode during
electrolysis
4. Example: Na +
Anion
1. Have negative
charge.
2. Have more electrons
3. Will move towards
anode during
electrolysis
4. Example: Cl __

6. Hydrophobic
Hydrophilic

7. Covalent bond
In contrast, atoms with the same
electronegativity share electrons
in covalent bonds and is the strongest
bond
Ionic bond
In ionic bonding, atoms transfer
electrons to each other.

8. Hydrogen bond:
• Hydrogen bond: Weaker bond than
covalent and ionic bonds but
stronger than Vander walls.
• A hydrogen bond is a primarily
electrostatic force of attraction
between a hydrogen atom which is
covalently bound to a more
electronegative atom or group,

9. Chemical bonds and interactions
Hydrophobic Interaction:
interaction of nonpolar
substances (fats) in the
presence of polar substances
(especially water)
Van der Waals Interaction:
Interaction of electrons of
nonpolar substances. Weak
interaction
non polar oil is not soluble in water

10. Acids and Bases
• The concentration of Hydrogen ions (H+)
describes the acidity
• The concentration of Hydroxide ions
(OH-) describes the basicity
• The pH scale is a convenient way to
express hydrogen ion concentration of a
solution
• Different charges attract each other and
like charges repel each other (Ionic
attraction)
??? H+ is greater than the number
of OH- in a …………solution

11. a pH of 3 is ten times more acidic than a pH of 4, and 100 times more acidic
than a pH of 5.
Similarly, a pH of 9 is 10 times more alkaline than a pH of 8, and 100 more
alkaline than a pH of 7.

12. pH Scale

13. Acids and Bases

15. The Molecules of Life
• All living things are made
up of four classes of large
biological molecules.
• THESE 4 are:
1. Carbohydrates,
2. Lipids,
3. Proteins
4. Nucleic acids

16. Monomers and polymers
• Macromolecules are large
molecules composed of
thousands of covalently
connected atoms
• Macromolecules are
Polymers, built from
monomers.

18. Types of biomolecules

19. Types of biomolecules

20. Carbon is the central element
• All biomolecules contain a Carbon chain or ring
• Carbon has 4 outer shell electrons (valence = 4)
• Therefore it’s bonding capacity is great
• It forms covalent bonds –hence, has strong bonds
• Once bound to other elements (or to other Carbons),
it is very stable
• Carbon linkages: They can be like single chains or
rings.
• The 4 types of biomolecules often consist of large
carbon chains .

21. Look at the various Functional
groups attached to carbon in
macromolecules
• Carbon binds to more than just hydrogen!!
• OH, NH2, PO4 are called ‘functional groups’!
Carbon binds to NH2
groups in amino acids
Carbon binds to OH
groups in sugars
Carbon binds to H2PO4
groups of nucleotides of DNA, RNA, and
ATP

22. Functional groups
in biomolecules

24. The Synthesis (making) and
Breakdown of Polymers
Making of a polymer:
A dehydration or condensation
reaction occurs when two
monomers bond together
through the loss of a water
molecule
Making of a polymer

25. The Synthesis (making) and
Breakdown of Polymers
• Breaking of Polymer:
Polymers are disassembled to
monomers by hydrolysis.
Addition of water to break the
bonds, a reaction that is
essentially the reverse of the
dehydration reaction.
Breaking of Polymer

28. Carbohydrates
• Carbohydrates include sugars and the polymers of sugars
• The simplest carbohydrates are monosaccharides, or single sugars
• Carbohydrate macromolecules are polysaccharides, polymers
composed of many sugar building blocks
• Monosaccharides have molecular formulas that are usually multiples
of CH2O
• Glucose (C6H12O6) is the most common monosaccharide
• Though often drawn as linear skeletons, in aqueous solutions many
sugars form rings
• Monosaccharides serve as a major fuel for cells and as raw material for
building molecules

30. Simple sugars
• Simple sugars are called
monosaccharides, made up of
single sugar molecules. Examples of these
are glucose, fructose, and galactose.
•
• Monosaccharides have molecular
formulas that are usually multiples of CH2O
• Glucose (C6H12O6) is the most common
monosaccharide.
• A disaccharide is formed when a
dehydration reaction joins two
monosaccharides .
• This covalent bond is called a glyosidic
linkage.
• Ex: Sucrose, maltose, lactose

31. Polysaccharides, the polymers of sugars, have storage and structural roles.
The structure and function of a polysaccharide are determined by its sugar
monomers and the positions of glyosidic linkages.
1. Storage polysaccharides :
Starch, a storage polysaccharide of plants, consists entirely of glucose
monomers.
The simplest form of starch is amylose
2. Structural Polysaccharides:
• Cellulose is a major component of the tough wall of plant cells
• Like starch, cellulose is a polymer of glucose, but the glyco sidic linkages differ
• Cellulose in human food passes through the digestive tract as insoluble fiber.
Chitin, another structural polysaccharide, is found in the exoskeleton of arthropods.
Chitin also provides structural support for the cell walls of many fungi
Complex sugars have more than 3 sugars

33. 2. Lipids
Hydrophobic
molecules

34. Lipids – rich source of energy (ATP)
• Fats are constructed from two types of smaller
molecules: glycerol and fatty acids
• Glycerol is a three-carbon alcohol with a hydroxyl
group attached to each carbon.
• A fatty acid consists of a carboxyl group attached to a
long carbon skeleton
• Structurally, lipids consist of Central core of one
glycerol joined to 3 fatty acid chains
• In a fat, three fatty acids are joined to glycerol by an
ester linkage, creating a triacylglycerol, or triglyceride
• They exhibit a high number of C-H bonds – therefore
much energy and non-polar

35. • When placed in water, lipids
spontaneously cluster together
• Biologically important lipids are fats,
phospho lipids, steroids.
• They help organize the interior content
of cells “phospholipids”
• Lipids have multiple functions in body,
the phospholipids form cell membrane
structures, some act as hormones
(steroid hormones), souce of Energy,
cushions organs and act as shock
absorbers

36. What are steroids and phospholipids?
Phospholipids?
• When phospholipids are added
to water, they self-assemble into
a bilayer, with the hydrophobic
tails pointing toward the interior.
• The structure of phospholipids
results in a bilayer arrangement
found in cell membranes.
• Phospholipids are the major
component of all cell
membranes
Steroids
• Steroids are lipids
characterized by a carbon
skeleton consisting of four
fused rings
• Cholesterol, an important
steroid, is a component in
animal cell membranes

38. Lipids do not
form true
polymers ?
Lipids are mainly made up
of hydrocarbons which form
non polar covalent bonds.
Structurally, lipids consist of
Central core of one glycerol
joined to 3 fatty acid chains

39. ESSENTIAL FATTY ACIDS:
• Certain unsaturated fatty acids are not synthesized
in the human body ; these must be supplied in the
diet. These essential fatty acids include the omega-
3 fatty acids, required for normal growth, and
thought to provide protection against
cardiovascular disease
HYDROGENATION
• Hydrogenation is the process of converting
unsaturated fats to saturated fats by adding
hydrogen. Hydrogenating vegetable oils also
creates unsaturated fats with trans double bonds.
These transfats may contribute more than
saturated fats to cardiovascular disease
• HUMANS AND OTHER MAMMALS STORE THEIR
FAT IN ADIPOSE CELLS