Proteins Revision.

  • Created by: ElishaG
  • Created on: 20-02-17 18:41
What is an amino acid?
An organic compound that contains both an amino group(NH2) and a carboxyl group(COOH). The monomer of polypeptides
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What is condensation?
A type of chemical reaction in which two molecules are joined by a covalent bond, water is released.
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What is the name of the bond that forms between amino acids?
Peptide bonds.
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What is hydrolysis?
A type of chemical reaction in which a molecule is broken down by the addition of a water molecule and breaking of a covalent bond.
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What is a polypeptide?
A polymer consisting of many amino acid monomers covalently bonded together.
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What are the names of the four structures that proteins have?
1)Primary. 2)Secondary.3)Tertiary.4)Quaternary.
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Describe the primary structure.
1)All proteins have one.2)Final structure of protein depends on the primary structure.3)It is the number, type and sequence of amino acids in a chain held by peptide bonds.4)Chain coils and folds as it is created.
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What is the primary structure determined by?
The DNA base sequence of a gene.
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What is the folding and coiling of the primary structure determined by?
The R groups present.
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Describe the secondary structure.
1)Hydrogen bonds form between oxygen atoms of the COOH group and hydrogen atoms of the NH2 groups.2)Peptide bonds still intact.3)When groups are close opposite charges attract, which folds and coils the chain, forming the secondary structure.
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What do secondary structures include?
1)Alpha helix. 2)Beta pleated sheet.
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Describe the tertiary structure.
1)Secondary structure may fold and coil, forming tertiary structure.2)Held in specific 3D shape by ionic bonds,disulfide bridges and hydrophobic/hydrophilic interactions.
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When do ionic bonds occur in the tertiary structure?
Between R-groups with positive or negative charges,which are quite strong.
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When do disulfide bonds occur in the tertiary structure?
Strong covalent S-S bonds between two amino acids containing sulfur.
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When do hydrophobic interactions occur in the tertiary structure?
When water repelling R-groups align away from water.
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When do hydrophilic interactions occur in the tertiary structure?
When water attracting R-groups align towards water.
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Describe the Quarternary structure.
Found in proteins with more than one polypeptide chain, how chains are arranged together.2)Sometimes a prosthetic group present.
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What is a prosthetic group?
A non-protein molecule that aids function.
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Summarise the primary structure.
1)Sequence/order of amino acids.2) Held by peptide bonds.
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Summarise the secondary structure.
1)Held by hydrogen bonds.2)Folds to alpha helix or beta pleated sheets.
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Summarise tertiary structure.
1)3D shape of protein due to interactions between R groups.2)Held by hydrogen bonds.3)Ionic bonds-oppositely charged ions.4)Disulfide bridges-between sulfur atoms.5)Hydrophilic/Hydrophobic interactions.
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Summarise quarternary structure.
1)More than one polypeptide chain.2)May be a prosthetic group present.
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What is a globular protein?
Proteins with spherical shape, soluble in water, often having metabolic roles in organisms. e.g. enzymes.
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What is a conjugated protein?
Globular proteins with a prosthetic group. e.g. haemoglobin.
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Describe haemoglobin.
1)4 polypeptide chains (2 alpha and 2 beta).2)Each chain contain haem prosthetic group.3)Haem prosthetic group has Fe2+ ion that can bind with O2.4)Each Haemoglobin can bind with 4 O2 molecules.
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Describe amylase.
1)An enzyme-globular protein.2)Produced in mouth and pancreas to digest amylose.3)Amylose hydrolysed to maltose as they're easier to transport.
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Describe insulin.
1)Globular, prouced in pancreas (in Beta cells of islets of Langerhans).2)Hormone released in response to high glucose levels.3)Target cells are liver and muscle.4)Binds to receptors, causes blood glucose levels to reduce.
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What is a fibrous protein?
A protein with a long,thin structure, insoluble in water. Often has structural role.
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Describe collagen.
1)Found in bone,cartilage,tendons and ligaments for tensile strength.
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Describe the primary structure of collagen.
Repeat sequence of 3 amino acids glycine-proline-X(any other amino acid).
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Describe the secondary/tertiary structure of collagen.
Glycine (33%) is smallest amino acid so allows polypeptide chain to be wound into tightly coiled, unbranched helix.
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Describe the quarternary structure of collagen.
1)3 of helical polypeptides wound around each other and held by H-H bonds.2)Triple helix molecules run parallel to others and disulfide cross links between R-groups hold molecules together forming fibres.
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Summarise globular proteins.
1)Coiled,spherical shape.2)Hydrophobic R groups point into centre of molecule.3)Only hydrophilic R groups are exposed outside molecules, so globular proteins are soluble.4)Have roles in metabolic reaction.5)E.g. enzymes.
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Summarise fibrous proteins.
1)Long chain running parallel.2)Hydrophilic R groups point to centre of molecule.3)Only hydrophobic R group is exposed so fibrous proteins are insoluble.4)Structural role.5)E.g. keratin
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Describe the test for proteins.
1)Blue biuret solution added to sample.2)If protein is present, colour changes to lilac.
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What are the two stages of paper and thin layer chromatography?
1)Stationary phase.2)Mobile phase.
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What is the stationary phase?
1)Paper made of cellulose or plastic sheet with layer of silica gel.2)Origin is marked and sample is separated.
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What is the mobile phase?
1)The solvent.2)Mobile phase flows over stationary phase, when they come into contact,carries biological molecules with it.
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What solvent is used for polar molecules?
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What solvent is usually used for non-polar molecules?
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What does the distance travelled by molecules depend on?
Their solubility-more soluble, further they will travel.
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How can the Rf value be calculated?
Distance travelled by component/distance traveled by solvent.
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