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Biology Semester 1 > Protein Synthesis (9) > Flashcards

Protein Synthesis (9) Flashcards

1
Q

during transcrption where are the nucleotides found ?

A

freely in the nucleus

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2
Q

what bases does RNA have ?

A

A
U
C
G

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3
Q

How does the template strand enable am mRNA trand tp be transcribed?

A

by using the complementary base pair rule

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4
Q

what is the function of RNA polymerase in transcription ?

A

to break apart the DNA strands

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5
Q

what enzyme breaks down nucleotides ?

A

DNAnuclease

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6
Q

where is the pre-mRNA cap placed ?

A

at the 5’

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7
Q

what is the cap composed of ?

A

phosphorylated 7-methyl guanosine

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8
Q

how is the cap placed on the end of the mRNA ?

A

by guanyltransferase

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9
Q

What 2 functions of the pre-mRNA cap ?

A

Blocks degradation of mRNA by 5’ exonucleases

promotes translation

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10
Q

what is the process called where a poly-A-tail is added to pre-mRNA ?

A

Polyadenylation

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11
Q

where on the pre-mRNA is the poly-A-tail added ?

A

at 3’

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12
Q

before the poly-A-tail is added to a pre-mRNA strand what must be done ?

A

pre-mRNA is cleaved near a signal AAUAAA at the 3’

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13
Q

what enzyme cleaves the pre-mRNA near the signal AAUAAA?

A

An endonuclease

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14
Q

approximately how many adenosine residues are added to the cleage site ?

A

200

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15
Q

by what enzyme are the adenosine residues added to the cleage site ?

A

poly-A polymerase

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16
Q

name 4 functions of the pre-mRNA poly-A-tail

A

protects the mRNA from degradation by 3’ exonucleases

also aids in termination of transcription

ensures export from the nucleus

and is important in translation

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17
Q

what is difference between an exon andd an intron ?

A

exons code for proteins and introns do not

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18
Q

how is final mRNA produced from pre-mRNA ?

A

Introns are spliced out

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19
Q

what can alternate splicing produce ?

A

Alternative splicing of pre-mRNA sequence can produce different proteins from the same gene

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20
Q

why is alternate splicing benificial for organisms ?

A

Less genes needed to code for more proteins

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21
Q

name 5 sections that mature mRNA contains

A 
5’ cap
5’ UTR (untranslated region)
Coding Region (to be translated into a protein)
3’ UTR (untranslated region)
Poly(A) tail
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22
Q

by what bonds are amino acids bonded together ?

A

covalent bonds

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23
Q

which two amino acids are considered small ?

A

glycine

alanine

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24
Q

which three amino acids are consiered nucleophillic ?

A

serine
threonine
cysteine

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25
name 5 amino acids that are considered hyrodrophobic
``` valine leucine isoleucine methionine proline ```
26
which three amino acids are considered aromatic ?
phenylalanine tyrosine trypyophan
27
which two amino acids are considered acidic?
aspartic acid | glutamic acid
28
which three amino acids are considered basic ?
histidine lysine arginine
29
which two amino acids are considered an amide ?
asparagine | glutamine
30
how does a nucleophile intercat with electrons ?
can donate them
31
DNA base triplets make up what ?
an amino acid
32
what is a codon ?
Base triplets in mRNA
33
how many possible codons are possible ?
64
34
the genetic code is degerenate . | what does thsi mean ?
More than one codon codes for each of the 20 amino acids
35
why is the genetic code being degenerate important ?
Gives tolerance against mutations
36
Some mRNA codons have special roles. | what is the role of AUG ?
Start codon
37
Some mRNA codons have special roles. | what is the role of UAG ?
Stop codon
38
Some mRNA codons have special roles. | what is the role of UAA ?
Stop codon
39
Some mRNA codons have special roles. | what is the role of UGA ?
Stop codon
40
what is the function of thransciption and translation ?
Transcription (DNA to RNA) and translation (RNA to protein) | are important processes for protein synthesis
41
substitution of bases may create a different amino acids and hence a different protein structure . name an example of this
Sickle Cell Anaemia The change in amino acid sequence causes haemoglobin to crystallise when oxygen levels are low, causing the sickle shape which gets stuck in small blood vessels
42
what can Accumulation of sickled cells in small blood vessels leads to ?
Downstream tissue ischaemia, causing pain and infarction In severe cases, organ damage and ischaemic stroke
43
how can Sickle Cell Anaemia be benifical ?
where sickled red blood cells provide protection against the malarial parasite, thus giving individuals with the mutation a selective advantage
44
what is happening to the number of Sickle Cell Anaemia within the USA ?
In the US where malaria is not endemic, the sickle cell trait is slowly disappearing from the African-American population
45
What do deletions or insertions into a DNA sequence lead to ?
frame shift | which can result in significant changes of protein sequence
46
where is DNA code transcribed into mRNA ? | where does protein sythesis take place ?
in the nucleus outside of the nucleus
47
what happens after transcription ?
mRNA leaves nucleoplasm via nuclear pores in the nuclear envelope and enters the cytoplasm
48
why can mRNA leave the nucleus but DNA can't ?
DNA is too big to leave the nucleus | mRNA is small and mobile
49
what happens after mRNA is in the cytoplasm ?
mRNA can then travel to ribosomes for translation of the DNA code into proteins
50
what are ribosomes composed of ?
ribosomal RNA (rRNA) and ribosomal proteins
51
what two sub units make up ribosomes and what do they produce
Consist of a 60S subunit and a smaller 40S subunit 60S + 40S = 80S
52
how many distict tRNA molecules are there ?
64 one for each codon
53
what is attached to each tRNA molecule ?
an amino acid
54
what is a tRNA bound to an amino acid is called ?
Aminoacyl tRNA / charged tRNA
55
what is a tRNA molecule which has had its amino acid removed known as ?
deacylated or uncharged tRNA
56
what is a tRNA molecule bound to growing polypeptide chain known as ?
peptidyl tRNA
57
during traslation what is initiation ?
binding of ribosome to 5’ end of mRNA and hydrogen binding of the anticodon of an aminoacylated tRNA carrying methionine on the AUG start codon
58
during traslation what is elongation ?
the addition of further amino acids to the growing polypeptide chain brought by corresponding aminoacylated tRNAs. Peptidyl transferase creates covalent peptide bonds between the amino acids
59
during traslation what is termination ?
when the stop codon (UAG, UAA, UGA) is reached and the peptide and ribosomal subunits are released
60
what enzyme during translation creates covalent peptide bonds between amino acids ?
Peptidyl transferase
61
how manyb places are there on the ribosome for tRNA at one time ?
3 places on the ribosome
62
how is energy used to form the bonds ?
its sourced from ATP
63
name two types of 2° structures
α-helices and | β-pleated sheets
64
where are proteins destined for used within the cytoplasm synthesised ?
on free ribosomes
65
where are proteins destined for secretion out of the cell synthesised ?
on ribosomes attached to the rough endoplasmic reticulum (RER)
66
what is the rough endoplasmic reticulum?
RER is a system of flattened cavities | Lined by thin membrane running from nuclear envelope and into the cytoplasm and with many ribosomes on its surface
67
where do the proteins go after synthesis on the ribosomes attached to the RER ? and how ?
transport to the Golgi apparatus as the proteins are incorporated into vesicles
68
what is the function of the Golgi apparatus ?
Post-translational modification of proteins occurs in the GA cavities. For example, glycosylation of membrane spanning proteins
69
what does the Golgi apparatus do to aid exocytosis ?
The now modified protein traverses the GA and is packaged into secretory vesicles Protein containing secretory vesicles move to the cell membrane, fuse with it and expel their contents into the extracellular space
70
describe Pre-mRNA Capping
The cap is composed of phosphorylated 7-methyl guanosine which is added to the 5’ end of the mRNA by guanyltransferase Ensures mRNA is exported out of nucleus Blocks degradation of mRNA by 5’ exonucleases Promotes translation
71
describe Polyadenylation of Pre-mRNA
The pre-mRNA is cleaved by an endonuclease near a signal AAUAAA sequence at the 3’ end appr. 200 adenosine residues are then added at the cleavage site by poly-A polymerase This poly-A-tail protects the mRNA from degradation by 3’ exonucleases The poly-A-tail also aids in termination of transcription, ensures export from the nucleus and is important in translation

Biology Semester 1 (6 decks)

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