BIOCHEMISTRY

Industrial Microbiology
Biomolecules

1. Carbohydrates
2. Lipids
3. Protein
4. Nucleic acids
Carbohydrates

The carbohydrates are a large and diverse group of organic compounds that includes sugars and starches.

Carbohydrates perform a number of major functions in living systems.

1. For instance, one type of sugar (deoxyribose) is a building block of deoxyribonucleic acid (DNA), the molecule that
carries hereditary information.

2. Other sugars are needed for the cell walls.

3. Simple carbohydrates are used in the synthesis of amino acids and fats or fatlike substances, which are used to
build cell membranes and other structures.

4. Macromolecular carbohydrates function as food reserves. The principal function of carbohydrates, however, is to
fuel cell activities with a ready source of energy.
Carbohydrates

❖ Carbohydrates are made up of carbon, hydrogen, and oxygen atoms.

❖ The ratio of hydrogen to oxygen atoms is always 2:1 in simple carbohydrates.

❖ This ratio can be seen in the formulas for the carbohydrates ribose (C5H10O5), glucose (C6H12O6), and sucrose
(C12H22O11).

❖ Although there are exceptions, the general formula for carbohydrates is (CH2O)n, where n indicates that there are
three or more CH2O units.

❖ Carbohydrates can be classified into three major groups on the basis of size: monosaccharides, disaccharides, and
polysaccharides.
Carbohydrates
a. Monosaccharides → simple sugar

❖ The number of carbon atoms in the molecule of a simple sugar is indicated by the prefix in its name.

❖ For example, simple sugars with three carbons are called trioses.

❖ There are also tetroses (four-carbon sugars), pentoses (five-carbon sugars), hexoses (six-carbon sugars), and
heptoses (seven-carbon sugars).

❖ Pentoses and hexoses are extremely important to living organisms.

❖ Deoxyribose is a pentose found in DNA. Glucose, a very common hexose, is the main energy-supplying molecule
of living cells.
Carbohydrates
b. Disaccharides
Disaccharides (di = two) are formed when two monosaccharides bond in a dehydration synthesis reaction
Carbohydrates
c. Polysaccharides
❖ Carbohydrates in the third major group, the polysaccharides, consist of tens or hundreds of monosaccharides
joined through dehydration synthesis.

❖ Unlike monosaccharides and disaccharides, however, they usually lack the characteristic sweetness of sugars such
as fructose and sucrose and usually are not soluble in water.

❖ One important polysaccharide is glycogen, which is composed of glucose subunits and is synthesized as a storage
material by animals and some bacteria.

❖ Cellulose, another important glucose polymer, is the main component of the cell walls of plants and most algae.

❖ Chitin is a polysaccharide that makes up part of the cell wall of most fungi and the exoskeletons of lobsters, crabs,
and insects.

❖ Starch is a polymer of glucose produced by plants and used as food by humans.

Lipids

❖If lipids were suddenly to disappear from the Earth, all living cells would collapse in a
pool of fluid, because lipids are essential to the structure and function of membranes
that separate living cells from their environment.

❖Most lipids are insoluble in water but dissolve readily in nonpolar solvents, such as
ether and chloroform.

❖Lipids provide the structure of membranes and some cell walls and function in energy
storage.
a. Simple Lipids
Simple lipids, called fats or
triglycerides, contain an
alcohol called glycerol and a
group of compounds known as
fatty acids. Glycerol molecules
have three carbon atoms to
which are attached three
hydroxyl (¬OH) groups. Fatty
acids consist of long
hydrocarbon chains
(composed only of carbon and
hydrogen atoms) ending in a
carboxyl (¬COOH, organic
acid) group.

A molecule of fat is formed

when a molecule of glycerol
combines with one to three
fatty acid molecules. The
number of fatty acid
molecules determines
whether the fat molecule is a
monoglyceride, diglyceride, or
triglyceride
a. Complex lipid

The primary function of lipids is to

form plasma membranes that enclose
cells. A plasma membrane supports the
cell and allows nutrients and wastes to
pass in and out; therefore, the lipids
must maintain the same viscosity,
regardless of the surrounding
temperature.
Lipids
b. Complex Lipids

❖ Complex lipids contain such elements as phosphorus, nitrogen, and sulfur, in addition to the carbon,
hydrogen, and oxygen found in simple lipids.

❖ The complex lipids called phospholipids are made up of glycerol, two fatty acids, and, in place of a
third fatty acid, a phosphate group bonded to one of several organic groups.

❖ Phospholipids are the lipids that build membranes; they are essential to a cell’s survival.
 Lipids
c. Steroids

❖ Figure 2.11 shows the structure of the steroid cholesterol,

with the four interconnected carbon rings that are
characteristic of steroids.

❖ When an ¬OH group is attached to one of the rings, the

steroid is called a sterol (an alcohol).

❖ Sterols are important constituents of the plasma

membranes of animal cells and of one group of bacteria
(mycoplasmas), and they are also found in fungi and plants.

❖ The sterols separate the fatty acid chains and thus prevent
the packing that would harden the plasma membrane at
low temperatures.
Proteins

❖ Proteins are organic molecules that contain carbon, hydrogen, oxygen, and nitrogen. Some also contain sulfur.

❖ Hundreds of different proteins can be found in any single cell, and together they make up 50% or more of a cell’s
dry weight.

❖ Proteins are essential ingredients in all aspects of cell structure and function. Enzymes are the proteins that speed
up biochemical reactions.

❖ Transporter proteins help transport certain chemicals into and out of cells.

❖ Other proteins are integral parts of cell structures such as walls, membranes, and cytoplasmic components.

❖ Still others, such as the hormones of certain organisms, have regulatory functions.
 Proteins
a. Amino Acids
❖ Amino acids are the building blocks of proteins. Amino acids contain at least one carboxyl (¬COOH) group and one
amino (¬NH2) group attached to the same carbon atom, called an alpha-carbon (written Cα)

❖ Although only 20 different amino acids occur

naturally in proteins, a single protein molecule can
contain from 50 to hundreds of amino acid
molecules, which can be arranged in an almost
infinite number of ways to make proteins of
different lengths, compositions, and structures.

❖ The number of proteins is practically endless, and

every living cell produces many different proteins.
 Proteins
b. Peptide Bonds

Amino acids bond

between the carbon
atom of the carboxyl
(¬COOH) group of
one amino acid and
the nitrogen atom of
amino (-NH2) group
of another. The
bonds between
amino acids are
called peptide
bonds.
Proteins
Levels of Protein Structure

❖ Proteins vary tremendously in structure.

❖ Different proteins have different architectures and different three-dimensional shapes.

❖ This variation in structure is directly related to their diverse functions.

❖ When a cell makes a protein, the polypeptide chain folds spontaneously to assume a certain shape.

❖ One reason for folding of the polypeptide is that some parts of a protein are attracted to water and other parts
are repelled by it.
Proteins
Levels of Protein Structure
Proteins are described in terms of four levels of organization: primary, secondary, tertiary, and quaternary.

1) The primary structure is the unique sequence in which the amino acids are linked together to form a polypeptide
chain

2) A protein’s secondary structure is the localized, repetitious twisting or folding of the polypeptide chain. This
aspect of a protein’s shape results from hydrogen bonds joining the atoms of peptide bonds at different locations
along the polypeptide chain.

3) Tertiary structure refers to the overall three-dimensional structure of a polypeptide chain. The folding is not
repetitive or predictable, as in secondary structure. Whereas secondary structure involves hydrogen bonding
between atoms of the amino and carboxyl groups involved in the peptide bonds, tertiary structure involves several
interactions between various amino acid side groups in the polypeptide chain.

4) Some proteins have a quaternary structure, which consists of an aggregation of two or more individual
polypeptide chains (subunits) that operate as a single functional unit.
Proteins
Levels of Protein Structure

The overall shape of a protein may be globular (compact and roughly

spherical) or fibrous (threadlike).
Nucleic Acids

DNA and another substance called ribonucleic acid (RNA) are together referred to as
nucleic acids because they were first discovered in the nuclei of cells. Just as amino acids
are the structural units of proteins, nucleotides are the structural units of nucleic acids.
Nucleic Acids

Each nucleotide has three parts:

▪ A nitrogen-containing base,
The nitrogen-containing bases are cyclic compounds made up of C, H, O, and N. The bases are named adenine (A),
thymine (T), cytosine (C), guanine (G), and uracil (U). A and G are double-ring structures called purines, whereas T, C,
and U are single-ring structures referred to as pyrimidines. Nucleotides are named according to their nitrogen-
containing base. Thus, a nucleotide containing thymine is a thymine nucleotide, one containing adenine is an
adenine nucleotide, and so on. The term nucleoside refers to the combination of a purine or pyrimidine plus a
pentose sugar; it does not contain a phosphate group.

▪ A pentose (five-carbon) sugar (either deoxyribose or ribose),

▪ A phosphate group (phosphoric acid).

Nucleic Acids
DNA

❖ According to the model proposed by Watson and Crick, a DNA molecule consists of two long strands
wrapped around each other to form a double helix (Figure 2.16).

❖ Every strand of DNA composing the double helix has a “backbone” consisting of alternating
deoxyribose sugar and phosphate groups. The deoxyribose of one nucleotide is joined to the phosphate
group of the next.

❖ The nitrogen containing bases make up the rungs of the ladder.

❖ The bases are held together by hydrogen bonds; A and T are held by two hydrogen bonds, and G and C
by three. DNA does not contain uracil (U).
The structure of DNA
Nucleic Acids
RNA
❖ RNA, the second principal kind of nucleic acid, differs from DNA in several
respects.

❖ Whereas DNA is double stranded, RNA is usually single-stranded.

❖ The five-carbon sugar in the RNA nucleotide is ribose, which has one
more oxygen atom than deoxyribose.

❖ Also, one of RNA’s bases is uracil (U) instead of thymine.

❖ The other three bases (A, G, C) are the same as DNA.

❖ Three major kinds of RNA have been identified in cells.

❖ They are messenger RNA (mRNA), ribosomal RNA (rRNA), and transfer
RNA (tRNA), each of which has a specific role in protein synthesis (see
Chapter 8).
Adenosine Triphosphate (ATP)
❖ Adenosine triphosphate (ATP) is the principal energy-
carrying molecule of all cells and is indispensable to the
life of the cell. It stores the chemical energy released by
some chemical reactions, and it provides the energy for
reactions that require energy.

❖ ATP is called a high-energy molecule because it releases a

large amount of usable energy when the third phosphate
group is hydrolyzed to become adenosine diphosphate
(ADP). This reaction can be represented as follows: