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IB Bio HL > D1.2 Protein Synthesis > Flashcards

D1.2 Protein Synthesis Flashcards

1
Q

Definition

mRNA

A

messanger RN
made as a strand that is complementary to template strand of DNA, it therefore has opposite bases (including uracil)

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2
Q

tRNA

A

transfer RNA
carries amino acids to the ribosomes where they are bonded together to form polypeptide chains

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2
Q

Where does transcription happen in euk. and prok.?

A

eukaryotes = inside nucleus
prokaryotes = cytoplasm

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2
Q

rRNA

A

ribosomal RNA
found in ribosomes and codes mRNA into amino acids

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2
Q

Transcription outlined

A
  1. Helicase breaks H bonds in region of DNA => seperates bases
  2. RNA polymerase moves template strands
  3. RNA polymerase matches complimentary RNA nucleotides (C & G , A & U)
  4. RNA nucleotides bind to form pre mRNA
  5. DNA behing RNA polymerase rejoins into double helix
  6. when RNA reaches stop codon = chain is terminated = pre mRNA detaches
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2
Q

sense and antisense strand

A

sense= other strand

antisense (created in 5 to 3, BUT starts at 3 to 5 on the DNA strand it is coding on)= strand where mRNA is built

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2
Q

Stages of transcription

A
  1. Initiation= RNA polymerase binds to DNA at start of gene = seperates two DNA sztrands by breaking H bonds
  2. Elongation stage = RNA polymerase build mRNA on one DNA strand
  3. Termination stage = terminator sequence in DNA is reached = mRNA released
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3
Q

mRNA facts

A

when a polypeptide is required = triplet code converted to mRNA

  • it is recyced when no longer needed (broken down by nucleases)
  • single stranded
  • contains ribose sugar
  • contains uracil
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4
Q

Definition

Translation

A

after transcription, it is the process by which mRNA combines with ribosomes where proteins are built

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5
Q

Translation outlined

A
  1. mRNA attaches to ribosomes of methionine (AUG)
  2. tRNA with complementary anticodon attaches to mRNA
  3. tRNA is attached to amino acid
  4. ribosome moves along mRNA bringing in 2 tRNA at one time
  5. enzyme & ATP used to join amino acid with peptide bond
  6. first tRNA released = collects other AA = repeated until stop codon
  7. many ribosomes can travel along mRNA at same times = polysome
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6
Q

tRNA facts

A
  • small
  • single stranded
  • clover shaped
  • each tRNA can carry different AA
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7
Q

stability of protein synthesis main molecules

A

mRNA<tRNA<DNA

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7
Q

Triplet

A

3 nucleotide bases in DNA

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7
Q

anticodon

A

3 bases at opposite end of tRNA that complementarily bind to codon on mRNA

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7
Q

Codon

A

3 nucleotide bases in RNA/protein

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7
Q

central dogma of molecular biology

A

theory that explains how genetic information flows from DNA to RNA to produce a biologically functional product

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8
Q

How many times does each base exist in one unit of codons and triplets

A

only once

genetic code is non overlapping= each base is only in one codon/triplet

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8
Q

genetic code facts

A
  • sequence of nucelotides
  • triplet code (found by francis crick)
  • non overlapping
  • degenerate => most AA have more than one triplet code
  • universal= same base triplet code for same AA in all living organisms
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9
Q

point mutation

A

Can occur during DNA replication or transcription and involves a single nucleotide base being altered, inserted, or deleted in a DNA or RNA sequence

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10
Q

frameshift mutation

A

addition or deletion of a base that causes a shift in the reading frame

11
Q

Sickle Cell Anemia

A
  • blood cells are in sickle shape instead of biconcave disk
  • causes heart stroke/attack, bone malformation, pneumonia
  • due to single base substitution of A to T
  • 6th triplet changes from GAG (GLU) to GTG (VAL)
  • prim & second structure of Beta subunit is altered
  • quaternary structure of haemoglobin changes
  • fibres are deformed
  1. long fibres poke into cell membrane = distorts shape
  2. ability to carry oxygen decreases
  3. block blood vessels
  4. puts strain on liver as it removes cells
  5. bone marrow has to continuously produce more
12
Q

Immediate effects of Sickle cell anemia

A
  1. long fibres poke into cell membrane = distorts shape
  2. ability to carry oxygen decreases
  3. block blood vessels
  4. puts strain on liver as it removes cells
  5. bone marrow has to continuously produce more
13
Q

Controlling transcription and translation

Transcription

A
  • limiting amount of mRNA produced from particular gene
  • post transcriptional events = regulate translation of mRNA
13
Q

Controlling transcription and translation

Directionality

A

Transcription= RNA polymerase builds mRNA 5 to 3

Translation= mRNA moves through ribosomes in 5 to 3 & only fits when orientated correctly

14
Q

Controlling transcription and translation

Initiation of transcription at promoter stages

A
  • RNA can only bind at promoter regions
  • transcription factors bind to promoter regions = allows RNA polymerase to bind
  • without TF = gene cannot be transcribed
15
Q

Controlling transcription and translation

Non coding sequence

A
  • 98% of human genome is non coding
    Made up of
  • regulators of gene expression
  • Introns = in eukaryotes; removed after transcription
  • telomers = found at ends of chromosomes
  • genes for tRNA and rRNA
16
Q

Modifications and splicing

A

based on fact that mRNA needs to be modified before translating
* pre mRNA contains two regions = exons and introns
* mRNA contains only one region = exons

Introns are removed by spliceosomes (large protein i n nucleus)
Exons are joined together

17
Q

Exons and introns

A

exon= protein coding region
introns = non protein coding region

18
Q

Alternative splicing

A

gene is spliced in multiple ways by combining different exons

=> creates different versions of proteins
=> Increased protein diversity from the same DNA

19
Q

Binding sites within protein production

A

P site= initiator tRNA binds there
A site = where incoming tRNA binds which is added to growing chain
E site = tRNA moves here after transferring AA to growing chain and exits ribosome

20
Q

Steps of ribosomes making proteins

A
  • Initiation: 5’ of mRNA binds to small ribosomal subunit
  • anticodon of intiator tRNA (carrying MET) binds to codon of mRNA
  • large ribosomal unit joins to assemble
20
Q

how proteins gain fucntionality

A
  • formed polypeptide packaged into vesicle by RER
  • moves to golgi apparatus
    => post-transformational modification
21
Q

Proteasome

A

total of all proteins made and used by the body

21
Q

How Insulin is made

A
  • 4 sections= A chain, B Chain, c peptide, signal peptide
  • pre proinulin enters through RER
  • signal peptide is removed
  • remaining pp= proinsulin
  • disulfide bridges form between A chain & B chain
  • Proinsulin is packaged into vesicle -> golgi
  • C peptide is removed
  • mature insulin remains
22
Q

Proteasomes function

A

uneeded/damaged proteins are broken down & recycled by hydrolysis

=> cell can maintain AA conc. & supply

23
Q

Translation baby language

A
  • mRNA binds to ribosome.
  • tRNA brings amino acids to ribosome.
  • Peptide bonds form between amino acids.
  • Ribosome moves along mRNA until stop codon reached.
24
Q

Outline the structure and function of the promoter regions of DNA.

A
  • short DNA sequence (typically TATA box)
  • binding site for RNA polymerase and other transcription factors
  • initiating transcription of the gene
25
Q

Describe the initiation of transcription, including the role of the promoter sequence, transcription factors, and RNA polymerase.

A
  • transcription factors bind to the promoter region of a gene
  • RNA polymerase at the start site
  • unwinds the DNA
  • synthesizes mRNA from the template strand in the 5’ to 3’ direction.
25
Q

Activator sequences

A

bind activator proteins that increase transcription of a gene.

26
Q

Repressor sequences

A

bind repressor proteins, which decrease or inhibit transcription

27
Q

transcription factors

A

proteins that bind to specific DNA sequences, like the promoter, to initiate or regulate the process of transcription.

28
Q
A
28
Q

five functions of noncoding DNA sequences

A

Regulation of gene expression (e.g., promoters, enhancers).
Splicing control (e.g., sites for spliceosomes).
Structural roles (e.g., telomeres, centromeres).
Developmental regulation (e.g., transcription factor binding sites).
Reservoir for genetic variation.

29
Q

location and timing of post-transcriptional modification of RNA.

A
  • nucleus before mRNA leaves to the cytoplasm for translation.
  • 5’ capping (methylguanosine cap).
  • Poly-A tail addition (adenine residues at the 3’ end).
  • RNA splicing (removal of introns and joining of exons).
30
Q

5’ cap

A
  • protects the mRNA from degradation
  • helps the mRNA bind to the ribosome for translation
  • helps in transporting the mRNA out of the nucleus.
31
Q

poly-A tail.

A
  • stability
  • mRNA lifespan.
32
Q

RNA splicing

A

Spliceosome removes introns, and joins exons

33
Q

reasons why proteins typically exist for a relatively short time within a cell.

A
  • Rapid degradation via the proteasome system.
  • Changes in cellular conditions (e.g., stress).
  • The protein’s role in short-term functions.
  • Post-translational modifications signaling degradation.

IB Bio HL (16 decks)

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