Concepts in Biochemistry, Chapter 3

1. Amino acids are the building blocks of proteins. There are 20 amino acids used in proteins. Fill in the blanks to describe the side-chain properties of various amino acids. __________ is the only amino acid that does not have a carbon atom in its side chain. The only cyclic amino acid is called __________. __________ has a hydrophobic side chain characterized by four carbons that are branched in the middle. The amino acid that has a pKa around 6 is called __________. The only amino acid with a two-ringed side chain is __________.

Answer:


2. At physiological pH, amino acids are zwitterions. Which of the following is a zwitterion?

A.A
B.B
C.C
D.D


3. Some amino acids have ionizable side chains. Which amino acid would have this titration curve?

A.Tyrosine
B.Aspartate
C.Cysteine
D.Glycine
E.Lysine


4. Amino acids are linked together in proteins by __________ bonds. This peptide bond formation reaction results in the loss of a __________ molecule, which makes this a condensation reaction. The amino acids that make up a protein are numbered from the ___ terminus to the ___ terminus. The protein size in Daltons can be determined by multiplying the number of amino acids by ___, the average size of an amino acid.

Answer:


5. Which of the following definitions are not properly matched with the respective proteins?
A.Amylase: Transport/storage protein
B.Collagen: Structural protein
C.Antibody: Immune system molecule
D.Hemoglobin: Transport protein
E.Actin: Required for muscle contraction


6. Additional chemical groups such as small organics or metals attached to proteins are called:
A.Subunit
B.a-chain
C.Residue
D.Prosthetic groups
E.Heme


7. The primary structure of a protein is its:
A.Shape
B.Sequence
C.Size
D.Charge


8. The secondary structure is a regularly repeating structure such as:
A.Collagen helix
B.Disulfide bond
C.a-helix
D.All of the above


9. The tertiary structure of a protein refers to the:
A.Three connected residues of a protein
B.Volume of protein
C.Protein elasticity
D.Interaction of secondary structures to form a compact unit


10. A protein's quaternary structure refers to:
A.Allosterism
B.Two or more polypeptide chains forming a multisubunit structure
C.Disulfide bond
D.Extended chain


11. To determine the sequence of a protein, several methods may be used. The preferred method, which labels and releases the N-terminal residue, is called:
A.Sanger method
B.Ninhydrin reaction
C.Edman degradation
D.CNBr cleavage


12. In order to study the characteristics of a protein, it is first necessary to isolate and purify the protein. Most of the methods employed involve isolating a protein based on its charge (as in __________ chromatography), its size, (as in __________ chromatography), or by selecting specific binding properties ( __________ chromatography). To visualize the purity of a protein solution __________ is used, wherein a protein is applied to a gel that is then subjected to an electric field.

Answer:



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