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Cell Bio > Exam 4 (Topic 15) > Flashcards

Exam 4 (Topic 15) Flashcards

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1
Q

5’ UTR (untranslated region)

A

noncoding sequence

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2
Q

Coding sequence

A

only exons

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3
Q

Three important proteins for fully processing mRNA before it can be moved to the cytoplasm

A
  1. cap-binding protein
  2. poly-A-binding protein
  3. EJC - Exon junction complex
    (All are important for regulating mRNA export and initiating translation)
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4
Q

Important for initiating translation

A
  1. cap-binding protein
  2. poly-A-binding protein
  3. EJC - Exon junction complex
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5
Q

The code is redundant means

A

more than one triplet can code for the same amino acid

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6
Q

3 nucleotide sequence of mRNA that codes for an amino acid

A

Codon

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7
Q

Only codon that signals the start of translation

A

AUG (methionine)

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8
Q

Three codon signal termination of translation

A

UAA, UAG, UGA

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9
Q

Do not code for any amino acid

A

Termination of Translation

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10
Q

Number of codons

A

61 possible amino acid codons
3 termination condons
(1 for start, 3 to terminate, 60 code for 20 amino acids)

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11
Q

mRNA can have up to 3 different

A

reading frames

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12
Q

How the triple code is read

A

Reading frames

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13
Q

The correct reading frame is determined by the

A

start codon (AUG)

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14
Q

Adapter molecules (about 80 nucleotides long) that bind to amino acid and also bind to mRNA

A

tRNA

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15
Q

Two very important regions

A

Anticodon and 3’CCA end

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16
Q

Base pairs in the reverse complement direction with the codon of mRNA

A

tRNA anticodon

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17
Q

Covalently couple each amino acid to its specific tRNA molecule

A

Aminoacyl-tRNA Synthetases

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18
Q

There is _____ unique synthetases

A

20 (one for each amino acid)

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19
Q

Use ATP hydrolysis to create a high energy bond between the amino acid and the tRNA 3’CCA end

A

Aminoacyl-tRNA Synthetases (this high energy bond is later used to power peptide bond formation)

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20
Q

Complex of Ribosomal proteins and rRNA

A

Ribosome (ribonucleoprotein)

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21
Q

The ribosome is composed of

A 
Large subunit (catalyzes the formation of the peptide bond)
Small subunit (matches the tRNA anticodon to the codons of the mRNA)
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22
Q

Three tRNA binding sites

A

A site, P site, E site

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23
Q

Makes up the core of the ribosome and do most of its catalytic function

A

rRNAs

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24
Q

rRNA contains a

A

peptidyl transferase catalytic core

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25
RNAs that can catalyze reactions
Ribozymes
26
Newly added tRNA binds to which ribosomal site?
P Site????
27
The small ribosomal subunit binds
Initator tRNA in the P site and additional proteins
28
This binds Initiator tRNA and additional proteins
Small Ribosomal Subunit
29
How do cells signal the start of translation?
1. The small ribosomal subunit binds (initiator tRNA in the P site carries methionine (met) and additional proteins: translation initiation factors) 2. The loaded small subunit binds to the 5' cap of mRNA 3. Initiator tRNA/small ribosomal subunit scans the mRNA in the 5'--> 3' direction to look for AUG 4. Once bound to AUG, Initiator factors dissociate from the small ribosomal subunit and then the larger ribosomal subunit attaches and completes the ribosome 5. Translation then begins with addition of tRNA in the A site and the first peptide bond forms
30
Translation Steps
1. New tRNA is added to the A site (Old tRNA is ejected from the E site) 2. Peptide bond is formed between new amino acids in P and A sites 3. Large subunit move forward (translocates) on the mRNA 4. Small subunit moves forward (translocates) creating empty A site
31
When the peptide bond is formed between new amino acids in P and A sites tRNA in A site
Now holds the polypeptide
32
When the large subunit moves forward on the mRNA
tRNA that was in P site is now in the E site and tRNA that was in A site is now in the P site
33
When the small subunit moves forward it
Creates empty A site and Step one is repeated again
34
Translation is terminated by
Three Stop Codons (UAG, UAA, UGA) | tRNA doesn't bind to stop codons
35
Proteins that bind to the A-site containing a stop codon
Release factors
36
Release factors function
Catalyzes the addition of water molecule to the polypeptide, polypeptide released from the tRNA, then the ribosome dissociates from the mRNA
37
How can we control gene expression?
mRNA production and degradation | Protein production and degradation
38
What governs gene expression
The length of time mRNA is allowed to exist governs its gene expression
39
When an mRNA is no longer needed
the mRNA gets degraded
40
Enzymes that degrade RNA
RNases
41
Lifetimes of mRNA are specified by
Specific sequence in the 3' UTR of the mRNA
42
Enzymes that degrade proteins
Proteases
43
Eucaryotes use
Proteosomes
44
Cylinder (trash can) complex of many proteases
Proteosomes
45
Proteosomes act primarily on proteins that are
Targeted for degradation by the addition of ubiquitin
46
Ubiquitin
A small protein itself that s added to proteins for degradation
47
The small ribosomal subunit binds
Initator tRNA in the P site and additional proteins
48
This binds Initiator tRNA and additional proteins
Small Ribosomal Subunit
49
How do cells signal the start of translation?
1. The small ribosomal subunit binds (initiator tRNA in the P site carries methionine (met) and additional proteins: translation initiation factors) 2. The loaded small subunit binds to the 5' cap of mRNA 3. Initiator tRNA/small ribosomal subunit scans the mRNA in the 5'--> 3' direction to look for AUG 4. Once bound to AUG, Initiator factors dissociate from the small ribosomal subunit and then the larger ribosomal subunit attaches and completes the ribosome 5. Translation then begins with addition of tRNA in the A site and the first peptide bond forms
50
Translation Steps
1. New tRNA is added to the A site (Old tRNA is ejected from the E site) 2. Peptide bond is formed between new amino acids in P and A sites 3. Large subunit move forward (translocates) on the mRNA 4. Small subunit moves forward (translocates) creating empty A site
51
When the peptide bond is formed between new amino acids in P and A sites tRNA in A site
Now holds the polypeptide
52
When the large subunit moves forward on the mRNA
tRNA that was in P site is now in the E site and tRNA that was in A site is now in the P site
53
When the small subunit moves forward it
Creates empty A site and Step one is repeated again
54
Translation is terminated by
Three Stop Codons (UAG, UAA, UGA) | tRNA doesn't bind to stop codons
55
Proteins that bind to the A-site containing a stop codon
Release factors
56
Release factors function
Catalyzes the addition of water molecule to the polypeptide, polypeptide released from the tRNA, then the ribosome dissociates from the mRNA
57
How can we control gene expression?
mRNA production and degradation | Protein production and degradation
58
What governs gene expression
The length of time mRNA is allowed to exist governs its gene expression
59
When an mRNA is no longer needed
the mRNA gets degraded
60
Enzymes that degrade RNA
RNases
61
Lifetimes of mRNA are specified by
Specific sequence in the 3' UTR of the mRNA
62
Enzymes that degrade proteins
Proteases
63
Eucaryotes use
Proteosomes
64
Cylinder (trash can) complex of many proteases
Proteosomes
65
Proteosomes act primarily on proteins that are
Targeted for degradation by the addition of ubiquitin
66
Ubiquitin
A small protein itself that s added to proteins for degradation

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