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MOL. BIO LEC > MB PRELIM LEC 4: PROTEINS > Flashcards

MB PRELIM LEC 4: PROTEINS Flashcards

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1
Q
  • Products of transcription & translation of nucleic acids
  • Polymers of amino acids
  • Manifest the phenotype directed by the nucleic acids
A

PROTEINS

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2
Q

AMINO ACIDS STRUCTURE

A

a. Carboxyl group (COO-)
b. Amino group (NH2 group bonded to C atom)
c. R (radical) group/side chains
d. Central C atom

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3
Q

amino acids become
completely +/- charged at certain pH
levels

A

pK values

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4
Q

pH where amino acids are
neutral

A

pI values

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5
Q

covalent C-N bonds that
connect amino acids in proteins

A

Peptide bonds

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6
Q

polymer of few amino acids

A

Peptide

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7
Q

Sequence of amino acids in proteins
which determines the nature & activity
of that protein

A

PRIMARY STRUCTURE

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8
Q

 Local interactions between amino acid side chains
 Ordered beta/ beta pleated sheets and less-ordered alpha helices, or random coils

A

SECONDARY STRUCTURE

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9
Q

Further folding secondary structures of
proteins

A

TERTIARY STRUCTURE

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10
Q

Protein structure consisting of more than one polypeptide

A

QUATERNARY STRUCTURE

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11
Q

CLASSIFICATION OF PROTEINS BASED ON COMPOSITION
- Only amino acids
EX: Albumins, globulins, histones

A

SIMPLE PROTEINS

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12
Q

CLASSIFICATION OF PROTEINS BASED ON COMPOSITION
- Proteins and nonprotein component
(prosthetic group)
EX: Lipoprotein (Low density lipoproteins), glycoproteins (mucin), metalloproteins (ferritin & hemoglobin)

A

CONJUGATED PROTEINS

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13
Q

CLASSIFICATION OF PROTEINS BASED ON COMPOSITION
- Simple (conjugated proteins having been partially hydrolyzed by acids,
enzymes or alkalis
EX: Proteases, fibrin

A

DERIVED PROTEINS

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14
Q

CLASSIFICATION OF PROTEINS BASED ON STRUCTURE
- Spherical
- Enzyme, messengers, transporters, regulators, & sometimes structural
EX: Hemoglobin

A

GLOBULAR PROTEINS

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15
Q

CLASSIFICATION OF PROTEINS BASED ON STRUCTURE
- Sheet-like filamentous
- Protection, structural role
EX: Collagen

A

FIBROUS PROTEINS

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16
Q

CLASSIFICATION OF PROTEINS BASED ON STRUCTURE
- Intermediate to fibrous to globular
- Blood clotting
EX: Fibrinogen

A

INTERMEDIATE PROTEINS

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17
Q

CLASSIFICATION OF PROTEINS BASED ON FUNCTIONS
- Act as catalysts
EX: Nucleases

A

ENZYMES

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18
Q

CLASSIFICATION OF PROTEINS BASED ON FUNCTIONS
- Transport substance across biological membrane
EX: Channel proteins (sodium ion channels)

A

TRANSPORT PROTEINS

19
Q

CLASSIFICATION OF PROTEINS BASED ON FUNCTIONS
- Reserves of metal ions and amino acids
EX: Ferritin

A

STORAGE PROTEINS

20
Q

CLASSIFICATION OF PROTEINS BASED ON FUNCTIONS
- Generate movement
EX: Myosin

A

MOTILITY PROTEINS

21
Q

CLASSIFICATION OF PROTEINS BASED ON FUNCTIONS
- Maintain cell shape
EX: Collagen

A

STRUCTURAL PROTEINS

22
Q

CLASSIFICATION OF PROTEINS BASED ON FUNCTIONS
- Protection against harmful agents
EX: Antibodies

A

DEFENSIVE PROTEINS

23
Q

CLASSIFICATION OF PROTEINS BASED ON FUNCTIONS
- Regulate different processes and activities
EX: Enzymes

A

REGULATORY PROTEINS

24
Q
  • Ordered sequence of nucleotides on a
    chromosome that encodes a specific functional protein
  • Fundamental physical & functional unit of inheritance
  • 1 st studied by tracking mutations
A

GENES

25
Q

GENES COMPOSITION:
- coding sequence of a gene

A

STRUCTURAL SEQUENCES

26
Q

GENES COMPOSITION:
- does not code for proteins, they regulate transcription of a gene
EX: promoter

A

REGULATORY SEQUENCES

27
Q

THE GENETIC CODE
 Gene’s nature was further clarified
 Deciphered by

A

Francis Crick,
Marshall Nirenberg,
Philip Leder,
Gobind Khorana,
& Sydney Brenner

28
Q

A dictionary to translate the 4-nucleotide sequence information in DNA to the 20- amino acid sequence information in proteins

1965:
 3-nucleotide code: 43 = 64 Triplets were assigned to amino acids
 Redundant (all except 2 methionine &
tryptophan, have more than 1 codon)
 Wobble in the 3rd position - Triplets coding for the same amino acid often differing in the 3rd base of the triplet
 Nonsense codons - Terminate protein synthesis: UAG, UAA, UGA

A

GENETIC CODE

29
Q

“There must be a molecular factor that can recognize components for both nucleic acid & protein sequences.” > tRNA (over 50 in humans & 40 in bacteria)

A

Adaptor hypothesis

30
Q

START OF PROTEIN SYNTHESIS:
- activation of the amino acids by covalent attachment to tRNA & catalyzed by 20 aminoacyl tRNA synthetases

A

tRNA charging

31
Q

START OF TRANSLATIONS

Classes of aminoacyl tRNA synthases:
- act on the 2’ OH of the tRNA
acceptor stem

CLASS I OR II?

A

CLASS I

32
Q

START OF TRANSLATIONS

Classes of aminoacyl tRNA synthases:
- act on the 3’ OH

CLASS I OR II?

A

CLASS II

33
Q

Site of protein synthesis

A

RIBOSOMES

34
Q

80S ribosomes

  • 60S large subunit (2.7 million daltons) = 5S rRNA + 5.8S rRNA + 28s rRNA + 40 ribosomal proteins
  • 40S small subunit (1.3 million daltons_ = 18S rRNA + 30 ribosomal proteins

PROKARYOTES OR EUKARYOTES?

A

EUKARYOTES

35
Q

70S ribosomes
- 50S large subunit (1.8 million daltons) = 5S rRNA + 23S rRNA + 34 ribosomal proteins
- 30S small subunit (1 million daltons) = 16S rRNA + 21 ribosomal proteins
- mRNA & initiating factors

PROKARYOTES OR EUKARYOTES?

A

PROKARYOTES

36
Q

TRANSLATION PROCESS:

BEGINNING of translation, when the small ribosomes subunit assembles with mRNA & then the large ribosomal subunit

A

INITIATION

37
Q

TRANSLATION PROCESS:

BINDING of charged tRNAs & formation of the peptide bond producing growing polypeptide

A

ELONGATION

38
Q

TRANSLATION PROCESS:

ENDING of translation, occurs when the complex encounters a nonsense codon

A

TERMINATION

39
Q
  1. SMALL RIBOSOMAL SUBUNIT first BINDS TO INITIATION FACTORS 3 (IF-3) & then to specific sequences near the 5’ end of mRNA (ribosomal binding site)
    - GUIDES THE START CODON (AUG) to the proper place in the ribosomal subunit
  2. INITIATION FACTOR 2 (IF-2) BOUND TO GTP & the INITIATING tRNAMet (eukaryotes) / tRNAfmet (bacteria, mitochondria, & chloroplasts), then joins the complex
  3. LARGE RIBOSOMAL SUBUNIT associates w/ HYDROLYSIS OF GTP resulting to formation of the initiation complex
     tRNAmet (eukaryotes)/ tRNAfmet (bacteria, mitochondria, & chloroplasts) is situated & can only bind to the peptidyl site (P site)
     All other tRNAs bind to
A

TRANSLATION: INITIATION

40
Q

accepts an incoming tRNA bound to an amino acid

A

A SITE

41
Q

holds a tRNA that carries a growing
polypeptide (first amino acid added is methionine
(Met)

A

P SITE

42
Q
  1. Trna carrying the next amino acid binds to the A site in a complex
  2. 1st formation of peptide bond between amino acids in A & P sites by transfer of the 1st amino acid to the next, generating a dipeptidyl-trna in A site (catalyzed by PEPTIDYL TRANSFERASE)
  3. Dipeptidyl-trna shifts from A site to P site (translocation) with the release of the “empty trna” from the E site
     During translation, the growing
    polypeptide begins to fold into its mature conformation
    - Assisted by molecular chaperons
A

TRANSLATION: ELONGATION

43
Q

TRANSLATION: TERMINATION
 Signaled by 1 of the 3
stop/nonsense/termination codons:

A

UAA, UAG, or UGA

44
Q

hydrolysis of the finished polypeptide from the final trna > release of the final trna from the ribosome > dissociation of large and small ribosomal subunits

A

TERMINATION/RELEASE FACTORS

MOL. BIO LEC (15 decks)

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