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Biology Semester 1 > Protein Synthesis (9) > Flashcards

Protein Synthesis (9) Flashcards

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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
Q

name 5 amino acids that are considered hyrodrophobic

A 
valine 
leucine 
isoleucine 
methionine
proline
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26
Q

which three amino acids are considered aromatic ?

A

phenylalanine
tyrosine
trypyophan

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27
Q

which two amino acids are considered acidic?

A

aspartic acid

glutamic acid

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28
Q

which three amino acids are considered basic ?

A

histidine
lysine
arginine

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29
Q

which two amino acids are considered an amide ?

A

asparagine

glutamine

30
Q

how does a nucleophile intercat with electrons ?

A

can donate them

31
Q

DNA base triplets make up what ?

A

an amino acid

32
Q

what is a codon ?

A

Base triplets in mRNA

33
Q

how many possible codons are possible ?

A

64

34
Q

the genetic code is degerenate .

what does thsi mean ?

A

More than one codon codes for each of the 20 amino acids

35
Q

why is the genetic code being degenerate important ?

A

Gives tolerance against mutations

36
Q

Some mRNA codons have special roles.

what is the role of AUG ?

A

Start codon

37
Q

Some mRNA codons have special roles.

what is the role of UAG ?

A

Stop codon

38
Q

Some mRNA codons have special roles.

what is the role of UAA ?

A

Stop codon

39
Q

Some mRNA codons have special roles.

what is the role of UGA ?

A

Stop codon

40
Q

what is the function of thransciption and translation ?

A

Transcription (DNA to RNA) and translation (RNA to protein)

are important processes for protein synthesis

41
Q

substitution of bases may create a different amino acids and hence a different protein structure .
name an example of this

A

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
Q

what can Accumulation of sickled cells in small blood vessels leads to ?

A

Downstream tissue ischaemia, causing pain and infarction

In severe cases, organ damage and ischaemic stroke

43
Q

how can Sickle Cell Anaemia be benifical ?

A

where sickled red blood cells provide protection against the malarial parasite, thus giving individuals with the mutation a selective advantage

44
Q

what is happening to the number of Sickle Cell Anaemia within the USA ?

A

In the US where malaria is not endemic, the sickle cell trait is slowly disappearing from the African-American population

45
Q

What do deletions or insertions into a DNA sequence lead to ?

A

frame shift

which can result in significant changes of protein sequence

46
Q

where is DNA code transcribed into mRNA ?

where does protein sythesis take place ?

A

in the nucleus

outside of the nucleus

47
Q

what happens after transcription ?

A

mRNA leaves nucleoplasm via nuclear pores in the nuclear envelope and enters the cytoplasm

48
Q

why can mRNA leave the nucleus but DNA can’t ?

A

DNA is too big to leave the nucleus

mRNA is small and mobile

49
Q

what happens after mRNA is in the cytoplasm ?

A

mRNA can then travel to ribosomes for translation of the DNA code into proteins

50
Q

what are ribosomes composed of ?

A

ribosomal RNA (rRNA) and ribosomal proteins

51
Q

what two sub units make up ribosomes and what do they produce

A

Consist of a 60S subunit and a smaller 40S subunit

60S + 40S = 80S

52
Q

how many distict tRNA molecules are there ?

A

64 one for each codon

53
Q

what is attached to each tRNA molecule ?

A

an amino acid

54
Q

what is a tRNA bound to an amino acid is called ?

A

Aminoacyl tRNA / charged tRNA

55
Q

what is a tRNA molecule which has had its amino acid removed known as ?

A

deacylated
or
uncharged tRNA

56
Q

what is a tRNA molecule bound to growing polypeptide chain known as ?

A

peptidyl tRNA

57
Q

during traslation what is initiation ?

A

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
Q

during traslation what is elongation ?

A

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
Q

during traslation what is termination ?

A

when the stop codon (UAG, UAA, UGA) is reached and the peptide and ribosomal subunits are released

60
Q

what enzyme during translation creates covalent peptide bonds between amino acids ?

A

Peptidyl transferase

61
Q

how manyb places are there on the ribosome for tRNA at one time ?

A

3 places on the ribosome

62
Q

how is energy used to form the bonds ?

A

its sourced from ATP

63
Q

name two types of 2° structures

A

α-helices and

β-pleated sheets

64
Q

where are proteins destined for used within the cytoplasm synthesised ?

A

on free ribosomes

65
Q

where are proteins destined for secretion out of the cell synthesised ?

A

on ribosomes attached to the rough endoplasmic reticulum (RER)

66
Q

what is the rough endoplasmic reticulum?

A

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
Q

where do the proteins go after synthesis on the ribosomes attached to the RER ?
and how ?

A

transport to the Golgi apparatus

as the proteins are incorporated into vesicles

68
Q

what is the function of the Golgi apparatus ?

A

Post-translational modification of proteins occurs in the GA cavities. For example, glycosylation of membrane spanning proteins

69
Q

what does the Golgi apparatus do to aid exocytosis ?

A

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
Q

describe Pre-mRNA Capping

A

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
Q

describe Polyadenylation of Pre-mRNA

A

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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