Topic 2: Molecular Biology (Student)
2.1
Essential Idea: Living organisms control their composition by a complex web of chemical reactions.
2.1 Molecules to Metabolism
i.
Molecular biology explains living processes in terms of the chemical substances involved.
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ii.
Try to explain process by looking at the structure of molecules and how they interact
Molecules important for living organisms:
o Water
o Carbohydrates: energy
o Lipids: energy, membranes
o Proteins: huge range of task including chemical reactions to enzymes
o Nucleic acids: DNA and RNA, genes
The relationship between genes and proteins is important! Do you know what it is?
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Molecular biologists break down biochemical processes into their component parts
(reductionism)
When they look at the sum of these reactions as a whole, they can study the emergent
properties of that system.
Carbon atoms can form four covalent bonds allowing a diversity of stable compounds to exist.
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15th most abundant on earth and has some special properties
o Can form covalent bonds with other atoms (sharing a pair of electrons)
o Can form up to four covalent bonds
o Can form large chains with carbon-carbon bonds that are very strong
o Can bind with infinite number of compounds
o Carbon has 4 valence electrons in its outer shell. It can easily gain or accept electrons
to become stable.
o Carbon can form single, double and triple bonds
Carbon is basic building block of life (fats, sugars, proteins, organic compounds)
Carbon can form rings (glucose) and chains.
Draw Carbon Atom Here:
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 Carbon has 4 valence electrons in its outer shell. It can easily gain or accept electrons to
become stable. This shell needs 8 electrons to be full so carbon can share with 4 different
atoms or make a double bond.
iii.
Life is based on carbon compounds including carbohydrates, lipids, proteins, and nucleic acids.
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Carbohydrates:
 Composed of carbon, hydrogen, and oxygen.
 The general formula of is (CH2O)n with a ratio of 2H:1C:1O
 Used for energy or structural purposes, end in –ose a lot.
Lipids:
 Composed of carbon, hydrogen, and oxygen.
 Insoluble in water but soluble in nonpolar solvents.
 Includes steroids, waxes, fatty acids, oils and triglycerides
 Function in long-term energy storage. Animal fat is a lipid that has six times more
energy per gram than carbohydrates.
 Important component of cell membranes.
 Triglycerides are fats if they are solid at room temperature or oils if they are liquid at
room temperature
Proteins:
 Contain carbon, hydrogen, oxygen, and nitrogen.
 Composed of one or more chains of amino acids.
 They are distinguished by their “R” groups in which some contain Sulphur.
Generalized amino acid
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Nucleic acid
 Contain carbon, hydrogen, oxygen, nitrogen, and phosphorus.
 Composed of smaller units called nucleotides that link together to form large
molecules. Two types: RNA (ribonucleic acid) and DNA (deoxyribonucleic acid).
 Each nucleotide has a base, a sugar, and a phosphate group.
 DNA has bases of adenine, guanine, cytosine, and thymine. Uracil replaces thymine in
RNA
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SKILL: Drawing molecular diagrams of: glucose, ribose, a saturated fatty acid and a
generalized amino acid.
Glucose
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The formula for glucose is C6H12O6.
The molecule is a six-membered
ring with a side chain.
Five carbon atoms are in 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 1,2,3 and 4 point
down, down, up and down
respectively, although on a form
glucose used by plants to make
cellulose the hydroxyl group on
carbon atom 1 point upward.
Ribose
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The formula for ribose is C5H10O5
The molecule is a six-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 the
number 1on the right.
The hydroxyl groups (OH) on
carbon atoms 1,2 and 3 point up,
down and down respectively
Fatty acid
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Main component of triglycerides
and phospholipids, nonpolar
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 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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Generalized amino acid
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A carbon atom in the center of the
molecule is bonded to four different
things:
- An amine group
- A carboxyl group which makes
the molecule an acid
- A hydrogen group
- The R group, which is the variable
part of the amino acid
Special notes:
Carbon is represented by C
Oxygen is represented by O
Single covalent bonds are shown with a –
Double covalent bonds are shown with a =
Special groups:
- Hydroxyl: -O-H or -OH
- Amine: -NH2
- Carboxyl: -COOH
- Methyl: -CH3
SKILLS: Identification of biochemical such as sugars, lipids, or amino acids from molecular
diagrams.
Molecule
Need to know:
Sugar
Monosaccharides
and
disaccharides
Examples:
Mono-
Di-
Poly-
Notice all composed of C,H, and O. Generalized formula is CH2O.
One ring are monosaccharide, two ring are disaccharide,
polysaccharides are composed of many monosaccharides joined
together. Each has hydroxyl group connected to ring.
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Lipids
Lipids contain C,
H, O as well, but
in different ratios
and much less O
then
carbohydrates.
Triglycerides,
phospholipids,
and steroids are
all examples of
lipids
Notice: Saturated fatty acid has no double bonds but unsaturated
does. Triglyceride has three chains coming off backbone,
phospholipids has two chains coming of backbone that contains
phosphate molecule, steroids composed of C, H, and O with many
rings connected together.
Amino
acids
Proteins also
contain C, H, O
and they all have
N. Some proteins
also contain S in
their R-groups.
Amino acids
linked together
makes a peptide
chain, linked by
peptide bonds
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Notice: contains elements C, H, O, and N. At one end it has carboxyl
group.
iv.
Metabolism is the web of all the enzyme-catalyzed reactions in a cell or organism.
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v.
Metabolism is the set of life-sustaining chemical reactions within the cells of living
organisms
These reactions are catalyzed by enzymes and allow organisms to grow and
reproduce, maintain their structures, and respond to their environments.
Many of these reactions occur in the cytoplasm, but some are extracellular including
digestion and the transport of substances into and between different cells.
The word metabolism can refer to the sum of all chemical reactions that occur in living
organisms.
Anabolism is the synthesis of complex molecules from simpler molecules including the formation
of macromolecules from monomers by condensation reactions
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Metabolism is divided into two components; anabolism (building large molecules from
smaller ones) and catabolism (breaking down of large molecules into their component
parts)
Anabolic reactions require energy as you are building large molecules from small ones
(takes energy to build things)
Some anabolic processes are protein synthesis, DNA synthesis and replication,
photosynthesis, and building complex carbohydrates, such as cellulose, starch and
glycogen.
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vi.
Catabolism is the breakdown of complex molecules into simpler molecules including the
hydrolysis of macromolecules into monomers.
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Catabolism are reactions that break down larger molecules into smaller ones or their
component parts
Catabolic reactions release energy (sometimes captured in the form of ATP)
Some examples of catabolic reactions are digestion of food, cellular respiration, and
break down of carbon compounds by decomposers
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