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Living organisms control their composition by a complex web of chemical reactions.
Objectives
Define the terms ‘metabolism’, ‘anabolism’ and ‘catabolism’.
Describe how the bonding of carbon allows different organic compounds to form.
Use ICT to create some organic molecules.
Key words: molecular / organic / metabolism / carbon / anabolism / catabolism
Understandings
Molecular biology explains living processes in terms of the chemical substances involved.
Carbon atoms can form four bonds allowing a diversity of compounds to exist.
Life is based on carbon compounds including carbohydrates, lipids, proteins and nucleic acids.
Metabolism is the web of all the enzyme-catalysed reactions in a cell or organism.
Anabolism is the synthesis of complex molecules from simpler molecules including the formation of
macromolecules from monomers by condensation reactions.
Catabolism is the breakdown of complex molecules into simpler molecules including the hydrolysis of
macromolecules into monomers.
Applications
Urea as an example of a compound that is produced by living organisms but can also be artificially
synthesised.
Skills
Drawing molecular diagrams of glucose, ribose, a saturated fatty acid and a generalised amino acid.
Identification of biochemicals such as sugars, lipids or amino acids from molecular diagrams.
MOLECULAR BIOLOGY
Molecular biology explains living processes in terms of the chemical substances involved.
,Molecular biology is a field of study that focuses on investigating biological activity at a molecular level.
clarifies the structure and function of chemical substances and determines their interactions as parts of living
processes.
Biological processes are tightly regulated by enzymes, whose expression is controlled by gene activation (DNA).
changes in activity are typically determined by signalling molecules (either endogenous or exogenous in origin).
ELEMENTS, MOLECULES AND COMPOUNDS
Atoms are the basic building blocks of matter.
made up of protons, neutrons and electrons.
Elements are made of one type of atom.
eg: carbon, oxygen, hydrogen.
Molecules are 2 or more atoms chemically bonded together.
they can be different or the same atom.
Compounds are two or more different elements chemically bonded together.
Three most common chemical elements:
Carbon: usually forms 4 covalent bonds with other elements.
Hydrogen: forms 1 covalent bond with other elements.
Oxygen: usually forms 2 covalent bonds with other elements.
ORGANIC COMPOUNDS
Carbon atoms can form four bonds allowing a diversity of compounds to exist.
Life is based on carbon compounds including carbohydrates, lipids, proteins and nucleic acids.
An organic compound is a compound that contains carbon and is found in living things.
All other compounds are defined as inorganic compounds.
Carbon
Carbon forms the basis of organic life due to its ability to form large and complex molecules via covalent bonding.
carbon atoms can form four covalent bonds that are particularly stable (catenation).
a covalent bond is formed when two adjacent atoms share a pair of electrons, with one electron
contributed by each atom.
covalent bonds are the strongest type of bond between atoms.
these properties allow carbon to form a wide variety of organic compounds that are chemically stable.
Main classes of carbon compounds
There are four principle groups of organic compounds that contribute to much of the structure and function of a cell:
Carbohydrates
most abundant organic compound found in nature.
composed primarily of carbon, hydrogen and oxygen in a common ratio: (CH2O)n.
, function as a source of energy (and as a short-term energy storage option).
important as a recognition molecule (e.g. glycoproteins) and as a structural component (part of DNA /
RNA)
Lipids
non-polar, hydrophobic molecules in a variety of forms (simple, complex or derived).
serve as a major component of cell membranes (phospholipids and cholesterol).
may be utilised as a long-term energy storage molecule (fats and oils).
may function as a signalling molecule (steroids).
Nucleic Acids
genetic material of all cells and determines the inherited features of an organism.
DNA functions as a master code for protein assembly, while RNA plays an active role in the manufacturing
of proteins.
Proteins
composed of one or more chains of amino acids.
make over 50% of the dry weight of cells.
are composed of C, H, O and N atoms (some may include S).
major regulatory molecules involved in catalysis (all enzymes are proteins).
may also function as structural molecules or play a role in cellular signalling (transduction pathways).
ORGANIC SUBUNITS
Ribose
the formula for ribose is C5H10O5
the molecule is a five-membered ring with a side chain.
, four carbon atoms are in the ring and one forms the side chain.
the carbon atoms can be numbered starting with number 1 on the right.
the hydroxyl groups (OH) on carbon atoms 1, 2 and 3 point up, down and down respectively.
Glucose
the formula for glucose is C6H12O6
the molecule is a six-membered ring with a side chain.
five carbon atoms can be numbered starting with number 1 on the right.
the hydroxyl groups (OH) on carbon atoms 1,2, 3 and 4 point down, down, up and down respectively.
Saturated fatty acids
the carbon atoms form an unbranched chain.
in saturated fatty acids they are bonded to each other by single bonds.
the number of carbon atoms is most commonly between 14 and 20.
at one end of the chain the carbon atom is part of a carboxyl group.
at the other end the carbon atom is bonded to three hydrogen atoms.
all other carbon atoms are bonded to two hydrogen atoms.
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