Propertes: linear sequence an number of amino acids in polypeptide chain. also decides structure and function of a protein.
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Proteins: Primary level (interactions)
Peptide bonds (type of covalent bond)
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Proteins: Secondary level (properties)
Formation of alpha helix or beta sheets
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Proteins: Secondary level (interactions)
Hydrogen bonds are formed between carboxyl group of one amino acid and amine group of another amino acid. Made possible ebcause polar covalent bonds in polypeptide make chain fold
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Proteins: Tertiary level (properties)
Further folding of the polypeptide, caused by R groups of amino acid giving it the 3D shape of a protein, either fibrous or globular.
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Proteins: Tertiary level (Interactions)
1. positively charged R-groups interact with negatively charged R-groups. 2. Hydrophobic amino acids orientate themselves towards centre of polypeptide, hydrophilic amino acids orientate themselves outward. 3. Polar R-groups form h-bonds
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Quarternary level (Properties)
Exists in proteins with more than one polypeptide chain. Multiple pp chains combine to form a single structure.
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Primary (structure, forces involved, importance)
Structure: Sequence of amino acids, Forces involved: Peptide bonds, Importance: determines all other level of organisation
Structure: alpha helices and beta-pleated sheets, Forces involved: hydrogen bonds formed between carboxyl and amino groups along the primary backbone, Importance: allows formation of globular proteins including enzymes
Structure: Shape produced by multiple polypeptide chains, Forces involved: bonds and other interactions between primary backbones of involved pp chains, importance: allows formation of large molecules with specific functions
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Fibrous proteins
Elongated with repeating structure, amino acid prevents folding maintaining an elongated shape, insoluble in water, durable
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Examples of fibrous proteins
Collagen - found in tendons, skin, walls of blood vessels, Keratin - found in hair.
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Functions of fibrous proteins
Structure (collagen), contractile functions (actin and myosin in muscles)
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Globular proteins
Round shape and water soluble,
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Examples of globular proteins
Enzymes, antibodies
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Functions of globular proteins
catalytic activity (enzymes), regulatory function (hormones), transport functions (haemoglobin)
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Polar and non-polar amino acids
Amino acids are often grouped according to the properties of their side chains (R-Groups). Amino acids with non-polar side chains are hydrophobic, polar amino acids are hydrophillic.
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Determining the specificity of an enzyme
Polar and non-polar amino acids are important in determining the specificity of an enzyme. Substrates can only combine with an active site when the shape and polar properties of the enzyme and substrate agree.
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Anabolic reactions
uses energy to build complex molecules 1. build complex molecules 2. are endergonic 3. are biosynthetic (photosynthesis for example)
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Catabolic reactions
Breaks down complex organic molecules with release energy 1. Break down complex molecules 2. Are exergonic 3.Are degradative (cellular respiration)
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Four functions of proteins with named example (1. catalysis)
1. Catalysis - enzymes are proteins each of which catalyses a specific chemical reaction. Rubisco catalyses the reaction that fixes CO2 from the atmosphere to create carbon compounds needed by living organisms
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Four functions of proteins with named example (2. Tensile strengthening)
2. Tensile strengthening - Collagen - A fibrous protein giving tensile strength to tendons, ligaments and skin. Helps to prevent cracks. Made of three polypeptides wound into a rope-like structure.
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Four functions of proteins with named example (3. Receptors)
Binding sites in membranes and cytoplasm for hormones, neurotransmitters, smells. Rhodopsin is a pigment, a membrane protein of the rod cells in the retina.
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Four functions of proteins with named example (4. Immunity)
Cells can make a huge number of different immunoglobulins known as antibodies. They detect antigens on bacteria and other pathogens and cause a response so that phagocytes can engulf the pathogen.
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