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Lecture 5 and 6- Proteins
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- 1What are the monomers that form polypeptides?Amino acids
- 2How many different amino acids are there?20
- 3Draw the general formula of an amino acid
- 4Which is the only amino acid that isn't chiral?Glycine
- 5What is an amino acid called if it has a positive and negative charge?Zwitterion
- 6What is the pH if both functional groups are protonated (NH3+ and COOH)?Acidic
- 7What is the pH is both functional groups are deprotonated (NH2 and COO-)?Alkaline
- 8What bond is formed between two cysteine molecules?Disulphide bridge
- 9Cysteine + Cysteine = ?Cystine
- 10What type of reaction occurs in the formation of cystine?Oxidation
- 11Which amino acid is always the first in a polypeptide chain?Methionine
- 12What bonds link amino acids together?Peptide bonds
- 13In which direction in a polypeptide sequence read?From the N terminal (amino terminal residue) to the O terminal (carboxyl terminal residue)
- 14What causes peptide bonds to be rigid and planar?Bond resonance
- 15Where is rotation possible in a polypeptide?
- 16Why is the trans- form most common?Rotation at C is limited due to steric clashes between R groups
- 17When does the cis- form occur?Glycine and 0
- 18What are the four levels of protein structure?Primary, Secondary, Tertiary and Quaternary
- 19What is the primary structure?The sequence of amino acids
- 20What is the secondary structure?The formation of alpha helices, beta sheets and loops/random coils due to the formation of hydrogen bonds
- 21What is the tertiary structure?Attractions cause the polypeptide to fold
- 22What is the quaternary structure?A protein consisting of two or more polypeptide chains assembled together
- 23Why is the primary structure so important?It dictates final protein structure because sequential arrangement of R groups will influence subsequent secondary, tertiary and quaternary structures. The protein structure then dictates the function.
- 24What can lead to a change in the primary structure?Genetic mutation
- 25Feature of the alpha helixCoiled like a spring, hydrogen bonds and amphipathic
- 26Features of the beta sheetFlat sheets, pleated, short runs of 5-10 amino acids, parallel or anti parallel, sheets held together by hydrogen bonds, the sheets are often connected by hairpin loops or turns
- 27The difference between parallel and anti parallel beta sheets?
- 28What are loops?They connect secondary structure elements, not connected by hydrogen bonds, frequently form part of active sites and the difference between structurally similar proteins occur almost exclusively in loops.
- 29What are motifs?They are particular arrangements of secondary structures that occur frequently within a polypeptide and can be associated with a particular biological function.
- 30What are domains?A poly peptide chain (or part of a polypeptide chain) that folds independently into a stable structure with its own hydrophobic core. They are formed fro several simple motifs. Each domain is associated with a distinct biological function.
- 31What bonds are responsible for the tertiary structure?Hydrogen bonds between R groups, ionic bonds between COO- and NH3+ of R groups, disulphide bridges between cysteine groups and hydrophobic interactions (hydrophobic R groups cluster inside proteins to shield themselves from water)
- 32What are Fibrous Proteins (Scleroproteins)?Long parallel fibres of secondary structures
- 33The Features of Fibrous ProteinsUsually insoluble and important for support and strength.
- 34Features of CollagenSuperhelices of glycine rich alpha helices, main protein in connective tissue, most abundant protein, strong and elastic
- 35What are alpha-keratins composed of?Composed of coiled-coils of two alpha helices that assemble together in larger fibres
- 36What is the structure of Beta Keratins: Fibroin?Layers of anti-parallel beta sheets rich in Ala and Gly, Small side chains interdigitate (interlock like fingers) which allows close packing
- 37What are Globular Proteins?Mixture of irregularly folded secondary elements to form a compact 3-D spherical shape
- 38What are Fibrous Proteins?Long parallel fibres of secondary structures
- 39Features of Globular ProteinsUsually soluble with inner hydrophobic core, transported easily in body fluids.
- 40What interactions are responsible for the quaternary structure of a protein?van der Waals
- 41What is haemoglobin constructed from?4 poly peptide chains (2 alpha, 2 beta) and 4 haem groups (porphyrin and Fe 2+)
- 42What mutation results in sickle cell anaemia?Beta chain mutation Glu becomes Val
- 43What is Thalassaemia?Underproduction of globin chains
- 44What is Porphyria?Underproduction of haem
- 45What are immunoglobins?Y-shaped proteins (antibodies) used by the immune system to identify and combat non-self .
- 46What is the structure of immunoglobins?4 chains linked by disulphide bridges ( 2 large heavy chains and 2 short light chains). The chain tips have variable structure and form specific binding sites for antigens.
- 47What is the role of chaperone proteins?Chaperone proteins assist the non-covalent folding of a protein.
- 48What can occur when proteins aggregate?Diseases can occur such as prion and amyloid disease (where soluble proteins become insoluble)
- 49Is the structure or sequence more strongly preserved in evolution?Structure
- 50What are the properties of alpha keratins?Strong and inextensible, insoluble and chemically inert
- 51What bonds form between the coiled coils of alpha-keratins?Disulphide bridges
- 52Where is fibroin found?Fibroin is found in silk cloth and spiders webs
- 53How are the beta sheets in fibroin joined together?Sheets joined by amorphous stretches which confer elasticity
- 54Give some examples of globular proteinsExamples include: myoglobin, haemoglobin and immunoglobins
- 55What do chaperone proteins prevent?They prevent aggregation, repair misfolded/heat damaged units
- 56Do chaperone proteins require ATP?YES
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- (Lecture 5 and 6- Proteins ) Biology- Semester 1 Fichas sobre Lecture 5 and 6- Proteins , creado por emma_moran el 23/12/2013.
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