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Proteins 1
| Question | Answer |
|---|---|
| Give an example of when proteins provide structure. | Collagen is the protein of bone, skin and tendon. |
| Give an example of when protein acts as a transport molecule. | Haemoglobin is the protein involved in oxygen transport. |
| What is the technical name for red blood cells? | Erythrocytes. |
| Describe the structure of haemoglobin. | 4 protein subunits per molecule. Each subunit contains a Haem group that can bind to one oxygen molecule. Haem is a prosthetic group. |
| What composes Low-density lipoproteins? | A phospholipid shell and a single molecule of apolipoprotein B. |
| What regulates the uptake of LDL particles? | The LDL receptor that binds to LDL and facilitates internalisation. |
| What causes hypercholesterolemia? | A mutation in the LDL receptor gene. |
| What is atherosclerosis? | A disease of the arteries in which fatty plaques develop on their inner walls, with eventual obstruction of blood flow. |
| Give an example of when proteins provide defence. | Antibodies are proteins that provide defence against infection. |
| Describe the structure of antibodies. | Two identical heavy chains and two identical light chains covalently linked by disulphide bonds. |
| What is the antigen recognition site? | A highly specific and tightly binds to the complementary antigen allowing recognition of foreign proteins by the immune system. |
| Give an example of when proteins act as biological catalysts. | Enzymes are proteins that regulate all biological systems. |
| What does a lysozyme do? | Catalyses the cutting of polysaccharide chains. |
| How does a lysozyme carry out its function? | Binds to polysaccharide chain and catalyzes the cleavage of a specific covalent bond and releases the product. |
| Give an example of when proteins regulate genes. | The Lac repressor is a protein that helps control gene expression. |
| What is the function of Lac repressor? | Controls production (expression) of proteins metabolising lactose in bacteria. |
| How does the Lac repressor carry out its function? | The repressor binds to DNA and prevents expression of the gene in the absence of lactose. |
| How many amino acids are there? | 20. |
| What do the chemical properties of the R group in an amino acid define? | The structure and function of the protein. |
| What are the basic amino acids? | Lysine, Arginine and Histidine. |
| What are the acidic amino acids? | Aspartate and Glutamate. |
| What are the polar amino acids with uncharged R groups? | Serine, Threonine, Asparagine and Glutamine. |
| What are the hydrophobic amino acids? | Alanine, Valine, Isoleucine, Leucine, Methionine, Phenylalanine, Tyrosine and Tryptophan. |
| Define an acid. | Any molecule that tends to release a hydrogen ion. |
| Define a base. | A molecule that readily combines with a hydrogen ion. |
| What is a main cause of hypercholesterolemia? | Mutations in the histidine residues of the LDL-receptor. |
| What is an example of receptor-mediated endocytosis? | The uptake of Low-density Lipoprotein. |
| Describe the process of the receptor-mediated endocytosis. | A reduction in the pH in the endosome causes a change in conformation of the LDL receptor due to the presence of histidine residues within the protein. LDL can no longer bind and is released into the lysosome. |
| What is a polypeptide? | A polymer of amino acids joined by peptide bonds. |
| What is a peptide bond? | A covalent bond formed when the carbon from the carboxylate group shares electrons with the nitrogen atom from the amino group of a second amino acid. |
| Does a peptide bond permit rotation? | No. |
| What is the definition of the secondary structure? | The initial folding pattern (periodic repeats) of the linear polypeptide. |
| What are the three main types of secondary structure? | Alpha-helix, Beta-sheet and Bend/Loop. |
| What stabilizes the secondary structure? | Hydrogen bonds. |
| What is the structure of the alpha-helix? | Right-handed and each turn has 3.6 amino acid residues. |
| How is the alpha-helix stabilized? | By H-bonds between amino and carboxyl groups of every 4th amino acid. |
| Define a beta-strand. | Extended stretches of 5 or more amino acids. Beta-strands are organized next to each other to make Beta-sheets. |
| What is a parallel beta-sheet? | If adjacent strands are orientated in the same direction (N-end to C-end). |
| What is an anti-parallel beta-sheet? | If adjacent strands run opposite to each other. |
| How is the bend/loop secondary structure formed? | Polypeptide chains can fold upon themselves forming a bend or a loop |
| How many amino acids are usually required for a turn in the bend/loop structure? | 4 amino acids. |
| What amino acid is frequently found in bends/loops? | Proline residues. |
Created by:
robertspedding
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