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Amino Acids and DNA
AQA A Level Chemistry
| Question | Answer |
|---|---|
| What does DNA stand for? | Deoxyribonucleic acid |
| What is an amino acid? | A biological molecule with two functional groups |
| What is DNA? | A large molecule containing genetic information |
| What is formed from different amino acids combined in one chain? | Proteins |
| What is the structure of DNA? | Two polymer chains made from nucleotides in the form of a double helix |
| Which functional groups do amino acids have? | NH₂ and -COOH |
| Draw the structure of lysine at low pH | |
| Draw the structure of alanine when it is in the presence of concentrated sodium hydroxide. | |
| Draw the zwitterion of alanine. | |
| Draw the structure of the organic product when valine reacts with methanol in the presence of concentrated sulfuric acid. | |
| Draw the structure of the organic product when alanine reacts with ethanoyl chloride. | |
| Draw the structure of the repeating unit formed when valine polymerises. | |
| Draw the structure of the organic product when an excess of bromoethane reacts with alanine. | |
| Describe the composition of proteins. | Proteins are sequences of amino acids joined by peptide bonds |
| List three levels of protein structure. | Primary, secondary (α-helix and β-pleated sheet), tertiary |
| Draw the structure of the tripeptide formed from ala-val-ala | |
| Draw the structure of amino acids formed when the given peptide is hydrolysed. | |
| Explain how hydrogen bonds, ionic bonds and sulfur-sulfur maintain the structure of proteins. | "Hydrogen bonding tends to occur between the partially negatively charged oxygen of -C=O of one amino acid and the partially positively charged hydrogen of -N—H on a different amino acid. Ionic bonds can form between side chain groups of amino acids. This |
| "Name and describe a simple method to separate a mixture of amino acids. | Thin-layer chromatography can be used to separate amino acids. This uses a plate coated with a thin layer of silica (SiO2) that acts as the stationary phase. The mixture dissolves in a suitable mobile phase and, as it moves up the plate, the amino acids |
| Give an equation used to calculate Rf values | Rf = distance moved by the spot / distance moved by the solvent |
| Amino acids are invisible. Give two methods of making them visible on the TLC plate. | The plate can be sprayed with a developing agent such as ninhydrin in order to make the spots visible. Alternatively, ultraviolet light can be shone on the plate in order to make the spots visible. |
| Describe the structure of an enzyme. | Enzymes are proteins that are folded into complex shapes that allow smaller molecules to fit in them. |
| Paclitaxel is a commonly used anticancer drug. Explain, in detail, how it can Enzyme-substrate complex interact with an enzyme. | "Enzymes contain an active site where the chemical reaction happens. This active site is specific to a particular substrate. When attached, the reacting molecule is held in the right orientation to react. It is important that the reacting molecule is |
| "How can drugs be used as enzyme inhibitors? | If a drug that mimics the shape of the substrate is introduced to the body it can block the active site of the enzyme to the substrate. This process is called enzyme inhibition. |
| Outline the role of computers in developing enzyme inhibitors | Computers can be used to model the shapes of proteins and enzymes and, therefore, can allow medicinal chemists to model the effect of introducing a particular enzyme inhibitor to that protein. |
| Why is a racemic mixture of a drug often less potent than an optically pure sample? | Active sites are stereospecific, which means that they are capable of binding to only one enantiomeric form of a substrate or drug. Therefore, 50% of a racemic mixture would not bind properly to the active site. |
| Describe the structure of a nucleotide. | Nucleotides are the monomers that make up DNA. They are comprised of a phosphate ion bonded to 2-deoxyribose, which is then bonded to one of the four DNA bases (cytosine, guanine, adenine and thymine). |
| Describe how nucleotides join together to form a single strand of DNA | Strands of DNA are formed when nucleotides polymerise. Covalent bonds between the phosphate group and the 2-deoxyribose of different nucleotides. The polymer takes the form of a sugar-phosphate-sugar-phosphate chain with different bases attached to the su |
| How do the single strands of DNA form together in a double helix? | Hydrogen bonds form between bases on each chain, which causes them to join together in a double helix |
| State the two pairs of DNA bases that are able to hydrogen bond to each other. | Adenine and thymine, cytosine and guanine |
| Draw the structure of cisplatin | |
| State the most common medicinal use of cisplatin. | Cisplatin is most commonly used as an anticancer drug |
| Outline some of the major side effects of cisplatin. | " Nausea, weakened immune system, mouth ulcers, loss of appetite, loss of fertility |
| " Why can drugs such as cisplatin have such adverse side effects? | Anticancer drugs are carried by blood around the body and have an impact on every cell they come into contact with. They have the greatest effect on rapidly dividing cells such as hair, reproductive cells and cells that line the stomach |
| How do oncologists mitigate against these side effects in their patients? | Dosages spread out at intervals of three weeks, regular checks of white blood cell count to lower risk of developing fever, steroids to lower nauseous feelings |
| Why might patients consider not taking cisplatin or other anticancer drugs? | Although cisplatin can increase the remaining time a patient has to live, it can severely lower the quality of life of the patient due to the side effects We, have to weigh up the balance between the quantity and quality of their time after diagnosis. |
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davenantchemistry
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