Lecture 10 Flashcards

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1
Q

translation

A

polymerization of amino acids into polypeptide chains

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2
Q

what does translation require?

A

-amino acids
-mRNA
ribosomes
-tRNA

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3
Q

transfer RNAs

A
  • adapt genetic information present as specific triplet codons in mRNA to corresponding amino acids
  • tRNA anticodons complements mRNA
  • carry corresponding amino acids
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4
Q

ribsosomes

A
  • have an essential role in expression of genetic information
  • consists of ribosomal proteins and ribomsomal RNAs
  • consists of large and small subunits
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5
Q

size of ribsosomes

A
  • 70S in prokaryotes

- 80S in eukaryotes

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6
Q

tRNAs

A
  • small in size and very stable
  • 75-90 nucleotides
  • transcribed from DNA tRNA genes
  • contain posttranscriptionally modified bases
  • have a cloverleaf structure
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7
Q

aminoacylation

A
  • tRNA charging

- before translation can proceed, tRNA molecules must be chemically linked to respective amino acids

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8
Q

aminoacyl tRNA synthetase

A

enzyme that catalyzes aminoacylation

  • 20 different kinds for each amino acid
  • highly specific and only recognize for its respective amino acid
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9
Q

what are the three steps of mRNA translation?

A

initiation, elongation, and termination

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10
Q

what does initiation require?

A
  • small and large ribosomal subunits
  • mRNA molecule
  • GTP
  • charged initiator tRNA
  • Mg2+
  • initiation factors
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11
Q

what are the initiation factors?

A
  • IF1 = blocks A-site
  • IF2 = GTPase
  • IF3 = inhibits small subunit binding
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12
Q

Shine-Dalgarno sequence

A

-precedes AUG start codon in bacteria and base-pairs with region on 16S rRNA of 30S small subunit, facilitating initiation

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13
Q

initiation complex

A

-small ribosomal subunit and initiation factors

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14
Q

termination

A

signaled by stop codons at the A site

-codons do not specify for an amino acid

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15
Q

FTP-dependent release factors

A

stimulates hydrolysis of polypeptide from peptidyl tRNA released from translation complex

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16
Q

translation in eukaryotes

A
  • ribosomes are larger and longer lived than bacteria
  • transcription occurs in the nucleus
  • translation occurs in the cytoplasm
17
Q

what proceeds the start codon in eukaryotes?

A

-eukaryotes mRNAs contain purine three bases upstream from AUG initiator codon

18
Q

Kozak sequence

A

increases efficiency of translation by interacting with initiator tRNA

19
Q

what is different with translation in eukaryotes?

A

requires more factors for initiation, elongation, and termination
-ribosomes are not free floating and are associated with the endoplasmic reticulum

20
Q

polypeptides

A

precursors to proteins

21
Q

proteins

A

polypeptides folded up into a 3-dimensional conformation

-most abundant macromolecules in the cell

22
Q

what do amino acids contain?

A
  • carboxyl group
  • amino group
  • R group on the central carbon
23
Q

what determines the type of amino acid?

A
  • the R group (side chain)

- it is either nonpolar, polar, and positively or negatively charged

24
Q

primary protein structure

A

sequence of amino acids

25
Q

secondary protein structure

A

alpha-helix and beta sheets

26
Q

tertiary protein structure

A

3 dimensional conformation

27
Q

quaternary protein structure

A

composed of more than one polypeptide chain

28
Q

posttranslational modifications

A

polypeptide chains modified once they have been synthesized

-crucial to functional capability of final protein product

29
Q

protein folding

A
  • not spontaneous

- dependent on chaperons (proteins that mediate folding process)

30
Q

hemoglobin and myoglobin

A

transport oxygen, which is essential for cellular metabolism

31
Q

collagen and keratin

A

structural proteins associated with skin, connective tissue, and hair of organisms

32
Q

actin and myosin

A

contractile proteins found in muscle tissue

33
Q

tubulin

A

basis of microtublin function in mitotic and meiotic spindle fibers

34
Q

enzymes

A
  • most diverse and extensive group of proteins
  • specialize in catalyzing chemical reaction
  • increase rate of chemical reaction reaching equilibrium
  • biological catalysis