Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

BioChem > Lecture 9 Part 1 > Flashcards

Lecture 9 Part 1 Flashcards

1
Q

Prokaryotic ribosomes are located where?

A

In the cytosol

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Eukaryotic ribosomes are located where?

A

Either the cytosol or on the cytosolic face of the ER.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What percentage of our cell’s chemical energy is required for protein synthesis?

A

90%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

How quick is protein synthesis?

A

100 residue peptide synthesized in 5 seconds.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

3 major advances in the genetic code knowledge

A

1) synthesis occurred on small ribonucleoprotein particles (ribosomes)
2) amino acids were activated when incubated with ATP
3) small nucleic acids could serve as an adapter to translate (tRNA)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What enzyme activates amino acids to become tRNAs?

A

Amino-acyl-tRNA-synthatase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Amino-acyl-tRNA-synthatase

A

attach the amino acid to the tRNA by esterification

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Codon

A

triplet of nucleotides that codes for a specific amino acid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How is the reading frame established?

A

established by the first codon in the sequence, the start codon (AUG)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

How many start positions for an mRNA strand? For a DNA strand?

A

mRNA - 3 different positions

DNA - 6 different positions (3 in each direction)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Direction of reading mRNA

A

5’ to 3’

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Why was no peptide formed with GGG?

A

because glycine forms a tetrameric complex in solution, thus the ribosome cant access and bind to it.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What amino acid is usually found at the beginning of a polypeptide?

A

Methionine since the AUG codon codes for it

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

How often does a termination codon occur?

A

once every 20 codons in each frame

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How many codons make an open reading frame?

A

50 or more

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the average molecular weight of an amino acid?

A

110 Da. since MW of 55,000 (55 kDa) requires a reading frame encoding 500 amino acids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Degeneracy and amino acids

A

an amino acid may be identified by more than one codon, but one codon specifies only a single amino acid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Wobble base/position

A

3rd base in the codon but first base in the anticodon.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

5’ of mRNA codon corresponds to what of tRNA?

A

the 3rd base on the tRNA or the 3’ end of the anticodon.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Which is the weak interaction between the mRNA and tRNA?

A

the wobble - the 3rd base of the codon and the 1st base of the anticodon.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is at the 3’ of a tRNA? at the 5’ end?

A

CCA which is then attached to an amino acid.

Many have a G nucleotide at the 5’ end.

22
Q

If C or A in the wobble position of the anticodon then?

A

then base pairing is specific.
C and G
A and U

23
Q

If U or G in the wobble position of the anticodon then?

A

binding is less specific and two codons may be read.
U - A or G
G - C or U

24
Q

When Inosine is in the wobble position of the anticodon?

A

three codons can be recognized (A, U, or C)

25
Q

What happens when an amino acid is specified by several different codons?

A

Codons that differ in either of the first two bases require different tRNAs.

26
Q

gag and pol genes of Rous sarcoma virus

A

two genes are encoded on a single mRNA but they are shifted out of frame by 1 base pair. Occurs about 5% of the time

27
Q

Ways in which one transcript leads to two genes?

A

Frameshifting, polycistronic, and alternative splicing

28
Q

Examples of frameshifting

A

gag and pol genes of Rous sarcoma virus, RF-2 release factor

29
Q

RF-2 release factor

A

required for termination of translation. Usually has stop at 26th codon. But if low levels, frameshift and entire protein is produced, allowing for termination at the previous stop codon.

30
Q

5 major stages of protein synthesis

A

Activation of amino acids, initiation, elongation, termination and ribosome recycling, and folding and posttranslational processing

31
Q

What is needed for activation of amino acids?

A

20 amino acids, 20 aminoacyl-tRNA synthetases, 32 or more tRNAs, ATP, and Mg

32
Q

What is needed for initiation?

A

mRNA, N-formylmethionyl-tRNA(Met), Initiation codon (AUG), 30S and 50S subunits, Initiation factors, GTP, and Mg

33
Q

What is needed for elongation?

A

Functional 70S ribosome, aminoacyl-tRNAs specified by codons, elongation factors, GTP, and MG

34
Q

What is needed in termination and ribosome recycling?

A

Termination codon in mRNA, release factors, EF-G, and IF-3

35
Q

What binds first in initiation? And what after?

A

mRNA binds to the small ribosomal subunit first and then to the initiating aminoacyl-tRNA. Then the large ribosomal subunit binds

36
Q

What is the energy in elongation?

A

GTP

37
Q

What ribosomal subunits in bacteria cells? In eukaryotes?

A

Bacteria: 30S and 50S to make a 70S
Eukaryotes: 40S and 60S to make a 90S

38
Q

What differentiates organisms into different phylum?

A

the 16S rRNA

39
Q

Number of different proteins and total proteins in 30S?

A

21 and 21

40
Q

Number of different proteins and total proteins in 50S?

A

33 different and 36 total

41
Q

T or F: proteins are the primary elements of a ribosome’s structure?

A

False, they are secondary.

42
Q

What is the order of the 3 binding sites on ribosomes? and what subunit does this occur on?

A

A: amino acid site
P: peptide site
E: exit site

50S

43
Q

What is the role of proteins in ribosomes?

A

supportive, structural role. play no part in catalysis.

44
Q

How many nucleotides in a typical tRNA?

A

73-93

45
Q

How are the amino acids attached to the 3’ terminal A residue?

A

by esterification

46
Q

How does activation of amino acids occur?

A

AMP is transferred from ATP to form an aminoacyl adenylate with release of PPi, the aminoacyl group is transferred to the correct tRNA.

47
Q

First step in activation

A

oxyanion on carboxylic acid on the amino acid attacks the alpha phosphorous, creating an adenylation.

48
Q

Class I mechanism

A

amino acid is attack at the carbonyl carbon and kicks off AMP. This attaches it to the 2’ OH of the A terminal, then a transesterification to move it to the 3’ OH by hitting the carbonyl carbon and breaking the ester linkage.

49
Q

Class II mechanism

A

3’ OH of the terminal A is activated and attacks the carbonyl carbon kicking off the AMP.

50
Q

Proofreading and aminoacyl tRNA synthetases

A

only few aminoacyl tRNA synthetases have proofreading ability and they are specific (ex. ILE and VAL), can detect charge.

51
Q

What is the second genetic code?

A

aminoacyl-tRNA synthetases need to be specific for tRNAs.

BioChem (14 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions