UNE BIOCHEM 1005 WEEK 1 QUESTIONS WITH CORRECT ANSWERS.

UNE BIOCHEM 1005 WEEK 1 QUESTIONS WITH CORRECT ANSWERS. What are the four different protein structures? 1. Primary 2. Secondary 3. Tertiary 4. Quaternary What is the primary structure of a protein? a linear sequence of amino acids in polypeptide chains which is written from the amino terminus (N-terminus) to the carboxyl terminus (C-terminus) What is the secondary structure made of? a-helix, b-sheets, and bends, turns, or loops How are alpha helices formed? They are formed when the carbonyl group of peptide bonds form a hydrogen bond with the amide hydrogen located 4 residues down the chain. Approximately how much of all secondary structures are a-helices? 1/3 What is not typically found in secondary structures and why? Proline, because it forms a non-traditional peptide bond and adds a "kink" in the helix How are beta sheets formed? They are formed when beta strands are connected laterally by at least two or three backbone hydrogen bonds How are the b-strands connected and and by what? They are horizontally by hydrogen bonds formed between C=O groups of either strand and NH groups of either strand B-sheets can either be _____________ or _________________. parallel or anti-parallel Where does the R group always protrude to? The top or bottom Depending on the R groups on the sides of the B-sheet, the sheet may have a ________________ and a ________________ side. hydrophilic and hydrophobic Where will the hydrophilic side of the sheet be? on the surface of the protein and be exposed to the polar H2O solvent. Where will the hydrophobic side of the sheet be? It will be buried in the protein and will only rarely be exposed to the polar H2O solvent. What are bends, turns, or loops? Short stretched areas of the polypeptide chain from these structures that are stabilized by hydrogen bonds (these are not random) What is tertiary structure? The total 3D conformation of an entire polypeptide chain including interactions between alpha helices, bets sheets, and any other loops, turns, or bends Give an example of a tertiary structure Rossman Fold Define structural domains They are defined as a section of protein sufficient to perform a particular chemical or physical task. They are defined regions with specific functions that are conserved in function and sequence across other proteins. What are motifs? common arrangements of secondary structures to generate a tertiary arrangement What is the quaternary structure? A combination of two or more tertiary subunits that work together as one functioning unit What are the homologous proteins? Myoglobin and Hemoglobin What do myoglobin and hemoglobin do? They bind oxygen How does hemoglobin travel? it travels in the blood inside a red blood cell to deliver oxygen to tissues What does myoglobin do? It remains in the heart and skeletal muscle cells to bind oxygen released by hemoglobin How are the tertiary and quaternary structures stabilized? By hydrophobic interaction, hydrogen bonds, and salt bonds What is apoprotein and give an example A protein missing its ligand or ligands ex: hemoglobin lacking heme-porphyrin ring What is holoprotein and give an example A protein with is ligand so it is able to function. EX: hemoglobin bound to heme What is myoglobin? a monomer that has 8 a-helices linked together by alpha-turns It has a ______________ pocket containing _______ with a ferrous iron atom (Fe+2) at its center for oxygen binding. hydrophobic; heme Fe+2 is always bound to ____________________ a histidine R- group of the a-helix What does the binding of Fe+2 do stabilizes the reduced state of iron when it binds to oxygen If heme is tightly bound to the globin, it is termed a _________________ prosthetic group Myoglobin binding is _________________ hyperbolic What is Hemoglobin composed of? 2 alpha and 2 beta subunits How many oxygen molecules can hemoglobin bind? 4 Hemoglobin is a _______________________ heterotetramer Each alpha and beta subunit has its own heme Hemoglobin can exist in two conformations. What are they? T-state or R-state In the T (tense) state, Hb has a ___________ affinity for O2.