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Clinically Based Concepts II > translation > Flashcards

translation Flashcards

1
Q

what is translation?

A

RNA -> protein, translating message into a final product: protein or polypeptide chain

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2
Q

what is the difference between polypeptide chain and protein?

A

some proteins are comprised of more than one polypeptide chain

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3
Q

what does the end product of translation represent?

A

the nucleotide sequence present in the gene of interest

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4
Q

what is special about the DNA sequence?

A

they occur in triplets that yield complementary triplets of nucleotides in the mRNA

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5
Q

what are each of the nucleotide triplets in mRNA known as?

A

codons

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6
Q

what is the genetic code?

A

all of the codons and the amino acids they code for

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7
Q

what are the two regions of tRNA that are special?

A
  1. anticodon that binds to a specific codon in mRNA
  2. carries amino acid that corresponds to the codon
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8
Q

how does tRNA appear in the cell with its specific amino acid attached?

A

tRNA ligase: by a family of 20 tRNA synthetase enzymes

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9
Q

true or false: each tRNA synthetase enzyme recognizes one and only one amino acid and attaches it to its appropriate tRNA

A

true

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10
Q

what happens when the enzyme has bound both serine and its tRNA?

A

charging/loading tRNA: the enzyme then uses the energy in ATP to create a bond between serine and the tRNA

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11
Q

what is the purpose of rRNA?

A

combines with other proteins to form a ribosome

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12
Q

what is the purpose of the ribosome?

A

provides the scaffolding needed to combine the appropriate amino acids in the right sequence to form the protein being synthesized.

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13
Q

what are the two subunits of the ribosome?

A

50S and 30S

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14
Q

what is the key step in the translation process of eukaryotic cells that involve 30S subunit, mRNA and a specific initiator tRNA carrying methionine?

A

the 30 S subunit moves along the mRNA until it locates and binds to the ‘start codon’, AUG. At this point, the two subunits come together creating a passageway through which the mRNA that is to be translated moves.

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15
Q

what is the combination of the two ribosomal subunits, the strand of mRNA, and the initiator tRNA comprise known as?

A

the ‘translation initiation complex’

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16
Q

describe the passageway of the ribosome through which tRNAs move and their anticodons bind to the codons on the mRNA via A,E, and P site

A

the first tRNA that helped initiate the process, has already bound to the start codon on the mRNA. This tRNA sits in what is known as the ‘P site’ within this passageway. Based on the second codon, the tRNA with the appropriate anticodon and amino acid enters the passageway. This tRNA then binds to the mRNA in the region of the ribosome called the ‘A site’ When this happens, an enzymatic component of the ribosome links the methionine on the first tRNA to the amino acid carried in by the second tRNA. This occurs at the region of the ribosome called the ‘P site’ and the two amino acids are linked with a peptide bond. Once this happens, the ribosome shifts over one codon to allow the first tRNA to leave through the ‘ E site ’. This allows the next tRNA to bind to its codon in the A site, and the process is repeated to elongate the polypeptide one amino acid at a time. In essence, each tRNA with the appropriate anticodon carrying the appropriate amino acid enters, binds, adds its amino acid to the polypeptide and then leaves.

17
Q

what are the three stop codons?

A

UAA, UAG and UGA

18
Q

true or false: tRNA recognizes the stop codons

A

false

19
Q

how does the process stop?

A

release factor enters A site, then an enzymatic reaction occurs that separates the tRNA in the P site from the polypeptide chain. As a result, synthesis of the polypeptide is terminated and it is released through an opening in the 50S subunit.
also causes the 50S and 30S subunits to separate from the mRNA and from each other

20
Q

what causes a primary protein structure to change shape?

A

hydrogen bonds form between the amino acids

21
Q

a hydrogen bond might form between the carbonyl group of one amino acid and the amino group of another one several amino acids down the chain, what could result if it happens several times along the length of the protein? what about hydrogen bonds between other amino acids in the chain

A

alpha helix
secondary structure: beta sheet, bend or other shapes

22
Q

what bonds affect tertiary structure?

A

covalent and non-covalent interactions

23
Q

what interactions account for the 3D shape of proteins?

A
  • hydrophobic portions of nonpolar amino acids orient themselves so they can avoid the aqueous environment of the cell.
  • two sulfur containing amino acids (methionine, cysteine, homocysteine and taurine) in different parts of the protein might form di-sulfide bonds with each other
  • positively and negatively charged side groups of amino acids could form ionic bonds.
24
Q

what is the quaternary structure?

A

several highly folded proteins are assembled together as subunits that carry out complex functions

25
Q

what are examples of quaternary structure?

A

hemoglobin proteins in red blood cells and ion channel proteins that transport specific ions across cell membranes

26
Q

what is the purpose of hemoglobin?

A

pick up oxygen in your lungs and release it where it is needed in your tissues.

27
Q

describe the process of how a hemoglobin is made

A
  1. nucleotides transcribed by RNA polymerase into mRNA that leaves the nucleus where it interacts with a ribosome
  2. codons in the mRNA are recognized by the anticodons in the tRNA molecules that carry the appropriate amino acids to the ribosome where they are linked by peptide bonds
  3. hemoglobin protein that then folds on itself in a precise fashion and forms a quaternary structure with 3 other similarly folded hemoglobin proteins
28
Q

what would happen if one of the DNA bases in the hemoglobin sequence was changed?

A

change results in a different amino acid being incorporated into the hemoglobin protein.

ex. thymine replaces an adenine in the DNA sequence. How would this cause problems? Well, it changes the sixth codon from GAG to GTG, which means that rather than having a tRNA carrying glutamic acid enter the picture, it’s replaced by one carrying valine.

29
Q

how does the one nucleotide change affect the hemoglobin?

A

sickle cell anemia: It causes hemoglobin molecules after they’ve released their oxygen molecules in the tissues to stick together and form long fibers. These fibers change those red blood cells from their normal bi-concave disc shape to that resembling a sickle

Clinically Based Concepts II (15 decks)

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