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Biology HL > D1.2 Protein Synthesis > Flashcards

D1.2 Protein Synthesis Flashcards

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1
Q

Define transcription.

A

The synthesis of RNA using DNA as a template

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2
Q

List the roles of RNA polymerases in the process of transcription. ​​

A

Attaches to DNA
Separates DNA
Produces mRNA molecules and links RNA nucleotides to form a polynucleotide

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3
Q

State the complementary base pairing utilized in transcription.

A

DNA RNA
A U
G C
C G
T A

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4
Q

Distinguish between the sense and antisense strands of DNA.

A

Antisense is the DNA strand, Sense strand is the RNA synthesized strand

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5
Q

Define gene expression.

A

The process by which genetic information in a gene (sequence in DNA) is used to synthesize a functional polypeptide

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5
Q

Outline how stability of the information stored in DNA is maintained.

A

Due to the strong covalent bonds between the nucleotides

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6
Q

Outline the major steps of gene expression.

A

Transcription : synthesis of RNA using DNA as a template
Translation : synthesis of polypeptides by ribosomes using genetic code of mRNA

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7
Q

Outline the role of transcription in regulating gene expression.​

A

Limit the amount of mRNA that is produced by a gene

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7
Q

State that the pattern of gene expression is how cells differentiate for specific functions.

A

Pattern of gene expression is how cells differentiate for specific functions

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8
Q

Outline the roles of mRNA, ribosomes and tRNA in translation.

A

mRNA binds to small subunit of ribosome to initiate translation
tRNA transfers amino acids from cytoplasm to ribosome
Ribosomes translate genetic code of mRNA into polypeptide

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8
Q

Define translation.

A

The synthesis of polypeptides through ribosomes

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9
Q

Describe the structures of mRNA and tRNA.

A

mRNA contains genetic code in form of codons (sequence of three nucleotides )
tRNA have an anticodon to bind to mRNA codons

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9
Q

State the location of translation in cells.​

A

At the ribosomes in the cytoplasm

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10
Q

Describe the structure of the ribosomes, including the small and large subunits and the names and roles of the tRNA binding sites.

A

Ribosomes are organelles composed of a small and large subunit and has three sites for tRNA called Peptidyl site, Aminoacyl site, Exit site and one site for mRNA
A site : tRNA brings a new AA into the ribosome to be added to the elongating polypeptide chain
P site : Holds tRNA with growing polypeptide chain and peptide bond is formed between the AA of the P and A site, releases the tRNA into the E site
E site : After tRNA enters the E site, it’s released from the ribosome.

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11
Q

State the complementary base pairing utilized in translation.

A

Cytosine Guanine
Adenine Uracil

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12
Q

Describe the formation of hydrogen bonds between codon and anticodon.

A

They use the complementary base pairing to form h-bonds

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13
Q

Define codon and anticodon.

A

Codon sequence of three nucleotides in mRNA that determine position of AA when a cell starts making a protein
Anticodon sequence of three nucleotides in tRNA that binds to corresponding codon and designates a specific AA

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14
Q

Explain the reason that a sequence of three nucleotides is required to code for the 20 amino acids commonly utilized by organisms.

A

Three nucleotides can form 64 different codons which codes for 20 different AA

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15
Q

Define codon, degenerate and universal as related to the genetic code.

A

Codon : sequence of three nucleotides in mRNA that determine position of AA when a cell starts making a protein
Degenerate : more than one codon may code for the same AA
Universal : all life forms use genetic code

16
Q

Outline the process of translation elongation, including codon recognition, bond formation and translocation.

A

Ribosome moves along mRNA from codon to codon through translocation
At each codon tRNA enters the ribosome and forms an AA through codon recognition
When two tRNAs are present in the ribosome, a peptide bond forms between their AA
The polypeptide chain grows till a stop codon enters the ribosome

17
Q

State the cause of sickle cell anemia, including the differences in the HbA and HbS alleles.

A

Single base substitution mutation for the alpha globin molecule of haemoglobin from an HbA allele which causes no problem to the HbS allele causing sickle cell trait.

18
Q

Define gene mutation.

A

Change to DNA sequence of an organism

19
Q

State the difference in RNA sequences in the transcription of the HbA and HbS alleles.

A

HbA has a glutamate as the 6th AA and HbS a valine as the 6th AA

20
Q

State the difference in amino acid sequences in the translation of the HbA and HbS alleles.

A

HbA has a glutamate and HbS a valine

21
Q

Outline the consequences of the HbS mutation on the structure and function of the hemoglobin protein.

A

HbS mutation alters structure and function of hemoglobin causing red blood cell sickling

22
Q

Describe the formation of the covalent bond between adjacent nucleotides during transcription.

A

The C-5 of a nucleotide is added to the C-3 end of the preceding nucleotide to form a phosphodiester (covalent) bond

23
Q

Discuss the symptoms of sickle cell disease.

A

Blocks small blood vessels

24
Q

State the direction of movement of the ribosome along the mRNA molecule.

A

During translation ribosome goes from 5’ to 3’

24
Q

State that RNA polymerases can only add the 5’ phosphate of a free nucleotide to the 3’ deoxyribose of the elongating strand.​

A

RNA polymerases can only add the 5’ phosphate of a free nucleotide to the 3’ deoxyribose of the elongating strand.

25
Q

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

A

A non-coding section of DNA where RNA polymerase binds to initiate transcription of a gene.

26
Q

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

A

At the promoter region, proteins such as transcription factors can bind in the correct orientation to allow RNA polymerase to also bind and to the promoter sequence and initiate transcription

27
Q

Compare the function of activator and repressor sequences within the promoter.

A

Activator sequences promote gene expression and repressor sequences prevent gene expression

28
Q

State that transcription factors are proteins that bind to the promoter.

A

Transcription factors are proteins that bind to the promoter

29
Q

Outline the location and timing of post-transcriptional modification of RNA.

A

post-transcriptional modification of RNA occurs in the nucleus and cytosol.

29
Q

Describe the function of the 5’ cap and poly-A tail.

A

To stabilize the mRNA a cap is added to the 5’ end and a poly-A-tail is added to the 3’ end.

29
Q

Define “coding” and “non-coding” sequences of DNA.

A

Coding DNA : gene sequences that code for mRNA and are expressed as functional polypeptides
Non-coding DNA : sections of DNA that do not code for functional polypeptides

30
Q

State that some transcription factors activate transcription while others inhibit transcription.

A

Some transcription factors activate transcription while others inhibit it

31
Q

Outline five functions of noncoding DNA sequences found in genomes.

A

Telomeres : repetitive base sequences at the ends of chromosomes. When DNA gets replicated, sequences at the end are lost, telomeres prevent important genes from being lost.
Regulators of gene expression : DNA sequences that regulate gene expression such as promoters (sequences that occur just before genes and act as a binding point for RNA polymerase)
Enhancers : dna sequences that are binding sites for proteins that increase the rate of transcription
Silencers : dna sequences that are binding sites for proteins that decrease the rate of transcription
Introns : sections of DNA or RNA that do not code for a protein and interrupt gene sequence

32
Q

Compare intron and exon sequences of genes.

A

Exons code for a polypeptide chain however introns need to be removed from RNA molecule

33
Q

Outline the process of RNA splicing. ​

A

Spliceosomes attach to both ends of an intron and cut it out. Exons are then spliced together to form mature mRNA.

34
Q

Describe the process of alternative RNA splicing.

A

Combines exons in various ways, creating diverse mRNA transcripts proteins from a single gene

35
Q

Outline the benefit of alternative RNA splicing.​

A

Allows a single gene to produce multiple different mRNA transcripts

36
Q

Outline the process of translation initiation.​

A

Small ribosomal subunit binds to the mRNA at the start codon
tRNA molecule with anticodon complementary to start codon binds to the mRNA
Large ribosomal subunit binds to small ribosomal subunit
tRNA is in P site, a second codon enters the A site
A tRNA complementary to second codon enters the A site
Peptide bond between two AA forms.

37
Q

Outline the two stages of modification of preproinsulin to form functional insulin.​

A

Formation of proinsulin : a single peptide is removed from preproinsulin within the RER to form proinsulin
Formation of insulin : proinsulin sent to the golgi apparatus, and is packaged into a secretory vesicle, within the secretory vesicle, a protein chain is removed from proinsulin to form an alpha and beta chain. Alpha and beta chain join by disulfide bonds to form functional insulin

37
Q

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

A

Because as soon as they aren’t required proteasomes recycle to them so they form required proteins.

38
Q

Outline the function of proteasomes in the recycling of amino acids.

A

Break down unneeded proteins to amino acids through hydrolysis and AAs are then recycled to synthesize proteins required by the cell

Biology HL (16 decks)

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