lecture 7

Question 1

protein

Answer 1

a polypeptide or group of polypeptides forming a molecule of specific biological function

Question 2

amino acid

Answer 2

one of the 22 different monomers that are attached to one another by peptide bonds to form proteins; chemically, a two-carbon carboxylic acid containing an amino group and a characteristic substituent on the alpha carbon

Question 3

peptide bond

Answer 3

a type of covalent bond linking amino acids in a polypeptide

Question 4

polypeptide

Answer 4

a polymer of amino acids bonded to one another by peptide bonds

Question 5

tertiary structure

Answer 5

the final folded structure of a polypeptide that has previously attained secondary structure

Question 6

quaternary structure

Answer 6

in proteins, the number and types of individual polypeptides in the final protein molecule

Question 7

denaturation

Answer 7

loss of the correct folding of a protein, leading (usually) to protein aggregation and loss of biological activity

Question 8

anticodon

Answer 8

a sequence of three bases in a tRNA molecule that base-pairs with a codon during protein synthesis

Question 9

aminoacyl-tRNA synthetase

Answer 9

an enzyme that catalyzes attachment of an amino acid to its cognate tRNA

Question 10

genetic code

Answer 10

the correspondence between nucleic acid sequence and amino acid sequence of proteins

Question 11

codon

Answer 11

a sequence of three bases in mRNA that encodes an amino acid

Question 12

wobble

Answer 12

a less rigid form of base pairing allowed only in codon-anticodon pairing

Question 13

codon bias

Answer 13

the non-random usage of multiple codons encoding the same amino acid; the relative proportions of different codons encoding the same amino acid vary in different organisms, same as codon usage

Question 14

start codon

Answer 14

a special codon, usually AUG, that signals the start of a protein

Question 15

stop codon

Answer 15

a codon that signals the end of a protein

Question 16

nonsense codon

Answer 16

another name for a stop codon

Question 17

open-reading frame (ORF)

Answer 17

a sequence of DNA or RNA that could be translated to give a polypeptide

Question 18

chaperone

Answer 18

a cytoplasmic particle composed of ribosomal RNA and protein, whose function is to synthesize proteins

Question 19

chaperone

Answer 19

a protein that helps other proteins fold or refold from a partly denatured state

Question 20

signal sequence

Answer 20

a special N-terminal sequence of approximately 20 amino acids that signals that a protein should be incorporated into or exported across the cytoplasmic membrane