Micr 3033 Ch. 4 Test 1 Questions with Answers
What common feature of alpha helices and beta sheets make them universal building blocks for proteins? - Answer-The hydrogen bonds that can be formed between the carbosxyl group of one amino acid and the N-terminal of another amino acid these bonds he...
What common feature of alpha helices and beta sheets make them universal building
blocks for proteins? - Answer-The hydrogen bonds that can be formed between the
carbosxyl group of one amino acid and the N-terminal of another amino acid these
bonds help form the structure and shape of alpha helix's and beta sheets and allow the
protein to be tightly packed.
Why do you suppose that only L-amino acids and not a random mixture of L- and D-
amino acids are used to make proteins? - Answer-L-amino acids more stable. D-amino
acids are toxic, H in acidic position have oppo steriochemistry.
Explain the coiled coil protein structure. - Answer-Repeated pattern of alternating
hydrophobic and charged amino acid residues causes creation of coil structure to
stabilize the two separate alpha helices
What do we mean by primary, secondary, tertiary and quaternary structure of proteins?
- Answer-Primary: amino acid sequence of the polypeptide chain. Held together by
covalent and peptide bonds.
Secondary: highly regular local sub-structures. (alpha helix and beta strand). Patterns of
hydrogen bonds between the main-chain peptide groups.
Tertiary: 3-dimensional structure of a single protein molecule. the folding of the protein
driven by the hydrophobic interactions.
Quaternary: larger assembly of several protein molecules. Polypeptide chains.
The protein structure in the figure below contains four Alpha helices arranged in a
bundle. Label each helix by number (1 to 4) starting going from the N terminus to the C
terminus. - Answer-
Why are the membrane-spanning regions of transmembrane proteins frequently alpha-
helical? - Answer-Because side chains have interphase with the membrane so they
have to be non-polar (hydrophobic)
Given that proteins act as molecular machines explain why coformational changes are
so important in protein function. - Answer-Each conformation allows for a different
function. proteins may have multiple functions because of multiple conformations.
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