Chemicals in Cells

Patterns in Nature
Topic 6: Chemicals in Cells
Part of the Patterns in Nature Module
Biology in Focus, Preliminary Course
Glenda Childrawi and Stephanie Hollis
DOT Point
 Identify the major groups of substances found in living cells
and their uses in cell activities
Chemicals in cells
Studies of the ultrastructure of cells reveal a variety of
organelles in the cytoplasm that function together so that a cell
can carry out life processes.
Our studies will now proceed to a chemical level, the chemicals that
make up these cell organelles.
Chemicals in cells
The chemical substances found in cells fit into two main
groups: organic substances and inorganic substances.
The term ‘organic’ should not get mixed up with modern day use of
the term ‘organic’ meaning a product of a farming method that avoids
the use of pesticides, artificial fertilisers and herbicides.
Inorganic Compounds
These are part of the inanimate (nonliving) world. These
substances do not contain the element carbon combined with
hydrogen and do not have long chains. Examples include:
 Mineral salts (calcium salts, sodium chloride and
 Water
 Some gases (carbon dioxide and oxygen) CO₂ contains carbon
but it has no hydrogen so is inorganic
Inorganic Compounds
Many inorganic substances are required for very specific
purposes. For example, calcium is important for bone function
and iron is an important component of haemoglobin (the
oxygen carrier in red blood cells).
Inorganic Compounds
Some mineral ions are enzyme cofactors (they must be present
for a particular enzyme function). For example, phosphorus
and nitrogen are essential for plant growth and water is a major
component of living tissue which must be present for life to
Organic Compounds
Chemical substances that are synthesised by living things and
contain atoms of carbon and hydrogen. Carbon atoms bond
very strongly with other carbon atoms and form long chains.
These chains are the basis of the large organic molecules made by cells.
Organic Compounds
Most organic compounds are very large molecules termed
macromolecules or polymers which include:
 Carbohydrates (sugars and starch)
 Lipids (fats and oils)
 Proteins
 Nucleic acid (DNA and RNA)
 Vitamins
Carbohydrates are the most common organic compounds in
nature. Carbohydrates consist of carbon, hydrogen and oxygen
atoms. These include:
 Monosaccharides
 Disaccharides
 Polysachharides
See Handout Pgs 101-102 of Text
 Are the simple sugars that are
the building blocks for the
more complex carbohydrates.
The most common is glucose
which is the main product of
photosynthesis and is the
molecule most commonly
used as an energy source in
plants and animals.
Sugar glucose: C₆H₁₂O₆
 consist of two joined monosaccharaides. These include
maltose, lactose and surcose. When carbohydrates are
transported from the leaves to other parts of the plant, it
is usually in the form of surcose.
 Large molecules in which hundreds to thousands of
monosaccharides are linked together. Some are used for the
storage of energy, others are used for structural purposes.
For example, starch consists of many joined glucose molecules and is used
in plants as a storage molecule which can be broken down when energy
is needed.
 Glycogen is a form of energy stored as granules in the
cytoplasm of animal cells.
Lipids are also made of carbon, hydrogen and oxygen atoms but
they are more energy efficient storage molecules than
Lipids are organic compounds that have an oily, greasy or waxy
consistency. They are relatively insoluble in water.
Most lipids are made of
a glycerol molecule
to which fatty acids
attach. Triglycerides
have three fatty acids
attached to each
Lipids may be fats (solid at room temperature eg: butter) or oils
(liquid at room temperature, eg: olive oil). Most fats are animal
products and oils are plant products.
Uses of lipids:
 Lipids form an extremely important structural part of all
membranes in cells
 Lipids are important biological fuels, storing large quantities
of energy for both plant and animal cells.
 Some lipids are essential structural parts of hormones
(chemical messengers produced by cells).
Proteins are large complex macromolecules and they are the
second most abundant chemical in cells. They too are made of
carbon, hydrogen, oxygen and often sulfur atoms.
Proteins are made up of one or more long chains of nitrogencontaining amino acids. These are the building blocks. There are
only 20 amino acids, but their arrangement provides a huge
variety of proteins.
DNA determines the actual sequence of amino acids in any protein.
Each chain of amino acids is called a polypeptide which are
held together by chemical bonds called peptide bonds.
One or more polypeptide can be twisted together into a particular shape
which results in the overall structure of a protein.
Proteins form structural components in cells and tissues.
Together with water, they form the basic structure of
protoplasm (the cytoskeleton) in cells and form parts of tissue
such as bone, hair and nails.
Proteins are also an important structural part of cell
membranes. Together with lipids, they regulate the passage of
substances across the cell membrane.
(These proteins are like the bouncers at the door)
Nucleic Acid
Nucleic Acids contain carbon, hydrogen and oxygen but also
contain nitrogen and phosphorus.
All nucleic acids are made up of simple repeating units
(monomers) called nucleotides linked together to form single
chains of RNA or double strands of DNA.
Nucleic Acid
Each nucleotide is made up
of a simple sugar (R ribose
or D deoxyribose), a
phosphate and a
nitrogenous base. It is the
sequence of bases which
differs, providing the
genetic code for a cell.
Nucleic Acid
DNA (deoxyribonucleic acid) stores the information that
controls the cell thereby the whole organism. Its responsible for
transmitting inherited information from one cell to another.
Nucleic Acid
RNA (ribonucleic acid) is found in small amounts in the nucleus
and in larger amounts in the cytoplasm. There are three types:
one, the messenger which is involved in passing on information
that is stored in DNA. The other types assist the message to be
translated into proteins (You’ll learn more about this in the
Answer the following questions in your notebook. Be prepared
to discuss next lesson.
 How do organic and inorganic compounds differ? Identify an
example of each.
 Carbohydrates and lipids contain carbon, hydrogen and
oxygen. How do they differ?
Complete 2.1 Prelim Dot Point text pg 29

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