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IB NOTES U2
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KEY OBJECT TO ACHIEVE 7 IN IB BIOLOGY HL
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2.1 Molecules to metabolism∑ - Understandings:
∑ - Molecular biology explains living processes in terms of the chemical
substances involved.
Involves the explaining of biological processes from the structures of the
molecules and how they interact with each other
There are many molecules important to living organisms including water,
carbohydrates, lipids, proteins, and nucleic acids
Proteins are one of the most varied macromolecules, performing many
cellular functions, including catalyzing metabolic reactions (enzymes)
The relationship between genes and proteins is important as well
Molecular biologists break down biochemical processes into their
component parts (reductionism)
When they look at the sum of all these reactions as a whole, they can
study the emergent properties of that system
β - Application: Urea as an example of a compound that is produced by
living organisms but can also be artificially synthesized.
Urea is a component of urine which is produced when there is an excess
of amino acids in the body; way to secrete nitrogen
A series of enzyme-catalyzed reactions produce urea in the liver, where it
is transported by the blood to the kidney, where it is filtered out and
excreted in the urine.
Urea can be produced artificially through different chemical reactions;
however, the product is the same.
Urea is mainly used as a nitrogen source in fertilizers
∑ - Carbon atoms can form four covalent bonds allowing a diversity of
stable compounds to exist.
Carbon has a few unique bonding properties - the most important of which
is its ability to form long chains of carbon. No other element can bond as
carbon does.
The reason carbon can do this is that carbon-carbon bonds are extremely
strong. This allows carbon to make up many of the basic building blocks of
life (fats, sugars, etc).
, Since carbon-carbon bonds are strong and stable, carbon can form
an almost infinite number of compounds
In fact, there are more known carbon-containing compounds than all the
compounds of the other chemical elements combined except those of
hydrogen (because almost all organic compounds contain hydrogen too).
Carbon can also form rings eg. glucose
The simplest form of an organic molecule is the hydrocarbon—a large
family of organic molecules that are composed of hydrogen atoms bonded
to a chain of carbon atoms. Eg. Methane
All bonding in hydrocarbons is covalent
Covalent Bonds are chemical bonds formed by the sharing of a pair of
electrons between atoms. The nuclei of two different atoms are attracting
the same electrons.
Carbon can form single, double and triple bonds
Carbon has 4 valance electrons in its outer shell.
∑ - Life is based on carbon compounds including carbohydrates, lipids,
proteins and nucleic acids.
Carbohydrates
Carbohydrates are composed of carbon, hydrogen, and oxygen
The general formula for carbohydrates is (CH2O)n.
Many carbohydrates are used for energy or structural purposes
Lipids
Lipids are compounds that are insoluble in water but soluble in nonpolar
solvents.
Some lipids function in long-term energy storage. Animal fat is a lipid that
has six times more energy per gram than carbohydrates.
Lipids are also an important component of cell membranes.
Some examples of lipids are triglycerides, steroids, waxes, and
phospholipids
Animal fats (saturated) are solid at room temperature and plant fats
(unsaturated) are liquid at room temperature
, Proteins
Proteins are composed of one or more chains of amino acids
All proteins are composed of carbon, hydrogen, oxygen, and nitrogen
Proteins are distinguished by their “R” groups. Some of these also
contain sulphur
Nucleic Acids
Nucleic acids are composed of smaller units called nucleotides, which
are linked together to form a larger molecule (nucleic acid).
Each nucleotide contains a base, a sugar, and a phosphate group. The
sugar is deoxyribose (DNA) or ribose (RNA). The bases of DNA
are adenine, guanine, cytosine, and thymine. Uracil substitutes for
Thymine in RNA
They are made from carbon, hydrogen, oxygen, nitrogen and
phosphorus
B - Skill: Drawing molecular diagrams of glucose, ribose, a saturated
fatty acid and a generalized amino acid.
Amino Acid
Composed of an amine (NH2) group, a carboxyl (COOH) group, and an
R group.
20 amino acids exist that compose all proteins
Each amino acid differs because the R groups are different
Glucose
Is a reducing sugar that contains C6H12O6
Most commonly found in a ringed structure and is the main product
formed by photosynthesis
Energy molecule used in aerobic respiration
A monomer of starch, glycogen, and cellulose
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