Biochemistry Final Exam Notes
CHEM225
Ch. 1: The Chemical Basis of Life
- Amino acids are a major type of biological molecule. Amino acids contain an amino group, a
carboxylic acid group and a side chain.
- Carbohyd
...
Biochemistry Final Exam Notes
CHEM225
Ch. 1: The Chemical Basis of Life
- Amino acids are a major type of biological molecule. Amino acids contain an amino group, a
carboxylic acid group and a side chain.
- Carbohydrates are a major biological molecule. Carbohydrates are monosaccharides or sugars.
General chemical formula: (CH2O)n, where n>3.
- Nucleotides are the building blocks of nucleic acids.
- Lipids have a variety of structures. One of the most important is cholesterol.
- Monomers link sequentially to form polymers.
• Three major kinds of biological polymers:
- Polypeptides and proteins
- Nucleic acid
- Polysaccharides
- Amino acids link to form polypeptide
and proteins. Amino acid resides are
connected via peptide bonds. Polypeptide
sequences are always read from the N
terminus to the C terminus.
- Nucleotide residues link via phosphodiester
bonds
- Polymers of nucleotides yield nucleic acids
- Polymers of sugars are polysaccharides linked with a glycosidic bond
Key concepts: Section 1-3
- The free energy of a system is determined by its enthalpy and entropy.
- Living organisms obey the laws of thermodynamics
- Enthalpy, H
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• The heat content of a system
• Units = J x mol-1
- Entropy, S
• A measure of the systems disorder or randomness
• Units= J x K-1mol-1
- Gibbs free energy, G
• A measure of the free energy of a system based on H and S
• Units = J x mol
Basics of Thermodynamics
- It is easier to measure thermodynamic changes than discrete values
- ∆G= ∆H -T∆S
• ∆G= Gibbs free energy change
- The sign of ∆G is meaningful, when ∆G <0, the reaction is spontaneous or exergonic.
- When ∆G > 0, the reaction is non spontaneous or endergonic.
Coupled Chemical Reactions
- ∆G is positive for the A—> B
transition. Non spontaneous
reactions do not generally occur.
∆G is negative for the B—>C
transition.
- Spontaneous reactions can be
coupled with non spontaneous
reactions so that the net reaction
occurs spontaneously.
Key Concepts: Section 1-4
- Modern prokaryotic and eukaryotic calls apparently evolved from simple non-living
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