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46 Cards in this Set
- Front
- Back
3 Structural proteins and their functions:
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collagen (bone, cartilage, tendon)
keratin (hair, nails, rhino horn) actin (muscle) |
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Enzymes:
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pepsin, amylase, carbohydrase, bromilase, protease, lipase (+>10 000 others)
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Transport (2):
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haemoglobin (oxygen), transferrin (iron)
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Pumps:
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EG Na+ K+ pump in cell membranes
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Motors (2):
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eg. myosin (muscle), kinesin (cilia)
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Hormones (8):
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estrogen, testosterone, LH, FSH, ADH, glucagon, insulin.
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Receptors:
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Rhodopsin (light receptor in retina)
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Antibodies:
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eg immunoglobulins
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Storage (2):
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eg albumins (egg white pure) in eggs and blood, caesin in milk
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Blood clotting (2):
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eg thrombin, fibrin
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Lubrication:
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glycoproteins in synovial fluid.
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Toxins:
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(organic poisons) e.g. diptheria toxin
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antifreeze:
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e.g. glycoproteins in arctic flea
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glycoprotein:
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type of protein with CH chain - antenna - sensor
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All proteins contain 4 elements:
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nitrogen, oxygen, carbon and hydrogen.
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amino acids are:
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the basic units (monomers) of proteins
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basic structure of an amino acid:
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NCC spine
2 Hs bonded to N R above and H below middleC x2bondto O above right C and bond to OH below OR H2N, C, COOH, R above and H below middle C |
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NH2 group is the...
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amino group (in chemistry, the naming group)
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COOH group is the...
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carboxyl group
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R group...
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varies between different amino acids. 20 R groups so 20 different amino acids.
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Glycine structure:
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H for R group.
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7 R groups:
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Simple (5), Basic (5), hydroxyl (2, end with OH), acidic (2, end with C bonded to O and x2 bonded to O- (extra proton)), sulphur (2, contain sulphur), ringed (3, all ringed but not only ringed amino acids) and cyclic (proline).
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What bond joins two amino acids together?
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Peptide bond. OH from bottom right of left mol and H from bottom left of right mol make water, C and N bond. The line between is peptide bond (glycosidic is when oxygen is left behind). NCCNCC is the pattern for di and poly spines.
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Primary Protein structure:
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1. Final configuration depends on the primary struct. - The Primary Structure is the number, type and sequence of amino acids in the chain. There are specific interations between different parts of the chain which give a final 3-dimensional shape of the protein.
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Secondary Protein Structure:
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H-bonds form between a.a.s in the cahin. Between O atoms of the COOH group (delta-) and Hs of the NH2 groups (delta+). When the groups are v close together they attract. This folds or coils the chain giving rise to the 2ndary structure. 2nd structs include the alpha-helix and the beta-pleated sheet.
Due to backbone interactions and is thus largely independant of primary sequence. |
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Tertiary Protein Structure:
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2ndary structure may then fold and coil forming the 3ry structure. This is held in a specific 3-d shape by electrostatic interaction (between rs with quite strong +/- charges) and disulphide bridges (covalent S-S bonds between 2 cysteine amino acids, which are strong).
Due to side chain interactions - thus depends on the amino acid sequence. |
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Quaternary protein structure:
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Found in prots containing more than one polypeptide chain - simply means how the different polypeptide chains are arranged together. Individual chains are usually globular, but can arrange themselves into a variety of 4ry structs eg haemoglobin, immunoglobulins, actin and tubulin.
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Haemoglobin structure:
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4 globular subunits arranged in a tetrahedral structure. Each sub contains one FE atom and can bind 1 O2 mol.
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Immunoglobulin structure:
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Proteins that make antibodies. 4 polypep chains in a y-shape. Held together via sulphide bridges. This shape allows antibodies to link antigens together, causing them to clump.
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Actin structure:
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One of prots found in muscles. Consists of many globular subunits arranged in a 2 helix to form long filaments.
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Tubulin structure:
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globular prot that polymerises to form hollow tubes called microtubules. These form part of the cytoskeleton and make cilia and flagella move.
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Fibrous proteins:
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Long chains of aas which are folded into a helix. Sometimes can be several polypep chains together. Can join to form long fibres. Insoluble (ext. R-groups are non-polar.) Provide strenght and flexibility - structural. Eg. keratin, collagen.
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Keratin:
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Keratin alpha-helix is basically a secondary structure. Microfibril (1 mol k is made of 3 a-helices). Hair fibre, macrofibril, microfibril.
Hair made up of many keratin molecules which form fibers. |
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Protein test:
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To test for protein in solution add Biuret reagent (alkaline copper sulphate). If protein is present the solution turns purple.
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What causes the 2ndary strucutre to differ in length from the primary?
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H bonds form between O atoms of Cooh groups and H atoms of NH2 groups, causing the chain to fold or coil.
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Explain what is meant by the tertiary structure of a protein?
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The way in which the whole molecule is folded or the way it forms a globular shape.
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Heating may affect the tertiary structure of a protein. Explain why.
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It causes the bonds which hold the tertiary structure together to break. The shape is no longer maintained / The protein is denatured.
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What is meant by a receptor molecule?
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A molecule in which another molecule can fit
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Explain how it's tertiary structure might allow a protein molecule to act as a receptor molecule
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The tertiary strucutre gives the receptor a particular shape, which provides the site into which another molecule can fit.
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Why electron can see protein but not light.
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The fibrils are thin / close together. The electron has a greater resolution than a alight microscope.
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Hydrolysis of protein -
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into amino acids. The reaction involves the addition of water.
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Suggest how a change in the structure of a protein could make it resistant to the action of protein - digesting enzymes.
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A change in the secondary structure would change the shape of the PrP molecule. No longer fits the active site of the enzyme.
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Biuret test in detial:
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Add 10 drops of each Biuret reagent (A and B) to a small sample of the protein. Shake the mixture. If it turns lilac protein is present.
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Suggest how a change in the structure of a protein could make it resistant to the action of protein - digesting enzymes.
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A change in the secondary structure would change the shape of the PrP molecule. No longer fits the active site of the enzyme.
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Biuret test in detial:
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Add 10 drops of each Biuret reagent (A and B) to a small sample of the protein. Shake the mixture. If it turns lilac protein is present.
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Amino acid structure:
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NCC, two Hbonds N, RaboveHbelow middle C, C 2bondO bondOH
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