DNA and RNA are both made of nucleotides. Proteins are made of amino acids. Transcription can be reversed but translation cannot.

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1 INFORMATION TRANSFER Information in cells Properties of information Information must be able to be stored, accessed, retrieved, transferred, read and used. Information is about order, it is basically the opposite of entropy. It works against the 2 nd law of thermodynamics and thus requires energy. The central dogma DNA and RNA are both made of nucleotides. Proteins are made of amino acids. Transcription can be reversed but translation cannot. Genome = DNA Transcriptome = RNA mrna messenger RNA trna transfer RNA rrna ribosomal RNA small nuclear RNA help to splice RNA micro RNA regulate rate of translation of RNA Proteome = protein Ion channels Receptors Enzymes Transcription factors Antibodies Biopolymers Anabolism the metabolic reactions that build or assemble more complex molecules from simpler ones (requires energy).

2 Catabolism all the chemical reactions that break down molecules (give energy). Catenation atoms of the same element forming long chains through chemical bonding. A biopolymer is a polymeric substance occurring in living organisms such as protein, cellulose or DNA. Linear biopolymers have a defined beginning and end and are synthesised in one direction only. The synthesis of a biopolymer is an anabolic process and during synthesis some of the monomer is lost leaving a residue which is incorporated into the growing chain. Carbon is a great basis for a biopolymer as it is stable, readily undergoes catenation and forms four bonds. Information in biopolymers Nucleic acids; chemical components and interactions Purines adenine, guanine Pyrimidines cytosine, uracil, thymine Nucleotides encompass a base, sugar and phosphate. Nucleosides encompass a base and a sugar. DNA deoxyribonucleic acid RNA ribonucleic acid Contains ribose a sugar with 5 carbons attached The numbering of carbons in a ribose are labelled with a prime i.e. 1 carbon Sugar-phosphate backbone negatively charged, hydrophilic in character The 5 phosphate is the start of the molecule The 3 OH is the end of the polymer The bond between the sugars is a phosphodiester bond and it contains energy

3 DNA vs. RNA and their roles DNA is less vulnerable than RNA for multiple reasons. RNA DNA Consequence 1. The RNA OH No OH group DNA less resistant to chemical/base backbone is vulnerable group at 2 attack backbone is snapped and complex breaks down 2. Uracil vs. thymine Uracil Thymine uracil is methylated to form thymine If uracil was used in DNA, there would be no way of detecting corruption of the code as uracil is spontaneously deaminated to form cytosine Thus, any uracils found in DNA are identified as mistakes and can be removed Uracils that should be in DNA are tagged (methylation) and are known as thymine 3. Double stranded DNA Single stranded Double stranded DNA has a template strand for repair Information is protected Major and minor grooves give protein access to the base pairs

4 Maintaining the double helix Strong bonds o Phosphodiester bond joins nucleotides Weak forces o Hydrophobic interactions result in base stacking o Electronic interactions allow twist of ladder as phosphate groups repel and bases attract = compromise o Ionic interactions allow strands to stay together o Van der Waals forces o Hydrogen bonding Features of proteins Peptide bond Hydrogen bonding dictates the structure of a protein.

5 Amino and carboxyl terminals The start of a peptide (amino terminal) is known as the N terminal and is positive at ph 7. The end of the peptide (carboxyl terminal) is known as the C terminal and this is negative at ph 7. Chemical properties of amino acid side chains Protein side chains can be hydrophobic/hydrophilic and positively/negatively charged at ph 7. Hydrophobic aliphatic Chains of -CH2- Neutral, uncharged e.g. Leucine Aromatic Rings with double bonds e.g. Phenylalanine Polar non-ionic -OH, -SH (thiol), or amide chains e.g. Serine Acidic Side chains with -COO- e.g. Glutamate Basic Side chains with -N+ e.g. Lysine Protein structure and their function Alpha amino acid The alpha amino acid is the standard form of all amino acids, with an alpha carbon, amino group, carboxyl group and a side chain. Amino acids are known as zwitterions because they have functional groups with opposite charges. Two amino acids combine by condensation polymerisation to form a dipeptide. As this occurs in cells an aqueous environment this reaction is thermodynamically unfavourable formed via translation on ribosomes so that water can be excluded from the active site and the reaction catalysed by RNA.

6 Proteins and forces 3D shape of proteins Proteins are only biologically active when they have the right shape. This 3D shape is maintained by: Hydrogen bonding peptide bonds, polar side chains Ionic interactions charged side chains Var der Waal s interactions all close contact Hydrophobic interactions hydrophobic side chains Protein folding Protein folding is dictated by the amino acid sequence and the environment. It allows charges to be buried within the protein. Primary structure Secondary structure Tertiary structure Quaternary structure Amino acid sequence Local structures Alpha helix, beta sheets 3D arrangement of the polypeptide Organisation of subunits Alpha helix and beta sheet Alpha helices are rigid, single polypeptide chains where all side chains face outwards. They also fit perfectly into the major groove of DNA! Enzymes Thermodynamics vs kinetics G = H T S where G is the change in free energy, H is enthalpy and S is entropy At equilibrium, G=0.