FREE BIOCHEMISTRY AND STUDY GAMES ABOUT AA

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PROTEIN STRUCT EXAM QUESTIONS

Actual Qs and Ans Expert-Verified Explanation

This Exam contains:

-Guarantee passing score -29 Questions and Answers -format set of multiple-choice -Expert-Verified Explanation

Question 1: Quaternary Structure

give an examples...

Answer:

-Proteins that contain 2+ subunits -Hemoglobin (Hb

Question 2: Sulfure containing amino acids

Answer:

Met and Cys

Question 3: Written form of a polypeptide chain

Answer:

N-terminus to C-terminus

Question 4: Amino acids with ionizable side chains (5)

Answer:

-R group can donate or accept protons -Asp, Glu, Lys, Arg, His

Question 5: Hemoglobinopathy

Answer:

• mutant hemoglobins giving rise to clinical problems
• unstable structure increases or decreases O affinity or increases rate of oxidation of heme Fe2+ to

Fe3+ Question 6: Collagen and the importance of amino acid comp and sequence, unusual amino acids and their function, importance of vitamin-C and iron in formation

Answer:

-most abundant protein (1/4 ttl proteins) -35% glycine + 11% alanine, w/ proline -4-hydroxyproline(V-C) + 5-hydroxylysine allow triple helix -glycine every 3rd sequence=structure and stability -peptide-proline,peptide-hydroxyproline=strength and rigid

Question 7: Reverse turns in B-pleated sheets

Answer:

-typically forms at water-peptide interface of protein surface -H-bonding between C=O of 1st and H-N of 4th amino acid stabalize -salt bridges,metal ions,disulfide bonds add more stability -often in antiparalell sheets

Question 8: Sharp bend in primary structure

Answer:

-Pro residue disrupts H-bonding forming bend and further disrupting H-bonding down stream Question 9: Amino acids with carboxylic side chains (2) and amino-like side chains (3)

Answer:

-negatively charged/ acidic at pH of 7 -Asp and Glu -Positively charged and basic -Lys, Arg, and His

Question 10: HbF v. HbA1

Why do the differences matter?

Answer:

-HbF= predominant form in fetus (2nd and 3rd trimester) =increases O affinity by reducing affinity for 2,3BPG = Histidine replaced with serine

-HbA1=tetramer of a2B2, most common in adults (90%)

Question 11: 2,3-BPG, CO2, and H influential behavior in Hb

Answer:

2,3-BPG- stabilizes T form by binding in central cavity H- binds to histidine,+ charge residues form salt bridges w/ aspartate, stabilize T form CO2- facilitates deprotonization in lungs and R form, binds to N terminal forms carbamates and T form

Question 12: Protein Domains

Answer:

-lobes, caused by folding of large polypeptide chains -segregate structure and/or function -domains connected by flexible linker regions -different enzyme activities sequestered in distinct, folded domains

Question 13: Post translational modification

Answer:

-modifications that occur after protein has been synthesized -occur while growing polypeptide is still attached to ribosome

Question 14: Primary Structure

Answer:

-Amino Acid sequence -determines 3D structure and biological function of protein -Amino (N) terminus or free amino goup at one end -Carboxyl (C) terminus or free carboxyl group at one end

Question 15: Supersecondary Structures aka Structural Motifs

Answer:

-assist in protein folding -interactions between newly folded and previously formed structures

Question 16: Oxygen binding to a heme...

Answer:

-binds 4 O -doesn't bind with equal affinity -as O increases, heme binds O more efficiently -binding O to a-Hb transforms Hb from T form to R form (valine residue moved from B-Hb binding sights)

-causes positive allosterism Question 17: Proteins in: Sickle Cell Anemia, Scurvy, and Prion disease

Answer:

Sickle Cell Anemia=valine instead of glutamate (sticky hydrophobic patch B subunits) Scurvy=insufficient Vit. C, crucial forming hydroxyproline and insufficient hydroxylysine (extracellular covalent cross links and glycosylation.Prion=misfolded protein

Question 18: Final functioning protein structure...

How are they stabalized?

Answer:

-Native structure -folded through favored pathways in cooperative manner -supersecondary structures, H-Bonding, salt bridges, hydrophobic forces and van der Waal's attractions -folding assisted by chaperones

Question 19: Secondary Structure

Answer:

-segment of polypeptide chain that has regular repeating structure -result from H-bonding interactions between C=O and H-N groups -a-helices and B-pleated sheets

Question 20: a-helices vs. B-pleated sheats

Answer:

a-helices-rod shaped,tight spirals (r-handed) -each C=O h-bonds to H-N 4 amino acids down chain B-pleated sheets-2+ polypeptide chains align side by side -interchain H-bonding of C=O and N-H groups -R groups project up and down -Paralell or Antiparal

Question 21: Nonpolar, aliphatic amino acids (7)

Answer:

-Hydrophobic and GENERALLY found in interior of water soluble proteins -Gly, Ala,Val, Leu, Ile, Pro, Met