(Physiology) Protein synthesis and RNA

Question 1

polypeptides

Answer 1

Made up of amino acids
Folds and bends (secondary structure)

PSTQ

A protein
Consists of one or more polypeptides (quaternary)

functioning protein is made up of many poly peptides

Question 2

what does one gene code for?
what is the ribosome used for and produce?
what do you get from Transcription and then translation

when is mRNA synthesized, where
then translation?

Answer 2

DNA directs protein synthesis
One gene codes for 1 polypeptide
Ribosome, Cellular machinery for translation
* Polypeptide synthesis

transcription- DNA to RNa
Translation- RNA to DNA

Transcription
mRNA is synthesized under the direction of DNA, in the nucleus

Translation
Synthesis of polypeptide under direction of RNA
On ribosome in cytosol

Question 3

What is the triplet code?
what are the two purposes of it

is it on mRNA

how are the sequences of bases determined in mRNA

Answer 3

The standard version of the genetic code, in which a sequence of 3 nucleotides in a DNA/RNA molecule codes for a specific amino acid in protein synthesis.

codon either codes for an amino acid to make a protein, or for a stop protein

A codon that codes for a specific amino acid. 3 nucleotides of mRNA

a gene determines sequence of bases along mRNA

Question 4

steps of RNA transcription

Answer 4

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produce mRNA

Initiation:
transcription factors must be in place on DNA strand for polymerase to bind
RNA polymerase binds to the promoter region of DNA and unwinds a specific section of DNA, exposing a set of bases.

Elongation:
RNA polymerase moves down the DNA, the SENSE strand, untwists the double helix and exposes 10-20 bases at a time.
Reading base pairs on DNA and adding in nucleotides, A-U——-C-G
once polymerase is past it it untwists.

Termination:
Polymerase rolls along until the end of the gene. it knows to fall off when it hits the POLYADENYLATION sequence. AAUAAA.
proteins cut mRNa free a bit farther down from end of gene and polyadenylation sequence
DNA strand cuts off mRNA and the DNA strand closes up

Question 5

Pre-mRNA processing after transcription and before it leaves the nucleus

what does the poly a tail and cap do?

RNA splicing

what do exons do

Answer 5

Intron(no genes) portions removed, joining exon portions.
Poly-A tail is added- a poly-A tail is added to the 3’ end
Guanine nucleotide cap is added to the 5’ end of mRNA

the tail and caps helps export mRNA, protects mRNA from degradation, and helps ribosomes attach

snRNP, small nuclear ribonucleoproteins, recognize where to splice, where introns are, form a SPLICEOSOME,

exons have a MODULAR STRUCTURE, and code for a different domain

Question 6

what is translation

what is mRNA and where does it bring the message

what is tRNA, is each on specific
what is an anticodon

how to get amino acid to bind to polypeptide

Answer 6

formation of a protein using mRNA as a template

mRNA carries message as a series of codons(3 nucleotides) into the ribosome to be synthesized

shuttle amino acids to building polypeptide
tRNA transfers amino acids to mRNA in the ribosomes so that a polypeptide chain can be created cytoplasm
each tRNA is specific to ONE AMINO ACID

An anticodon is found on tRNA with an amino acid that binds with codons from mRNA with complementary bases and then releases the amino acids to be attached to a polypeptide chain through peptide bonds.

getting tRNA to bind with the correct amino acid using an enzyme, which can then be carried to ribosome
—–use Aminoacyl-tRNA synthetaseJoins each amino
acid to the correct tRNA Binding site specific to amino acid

Question 7

1. what do ribosomes do
2. what are the 3 sites
3. polyribosomes?
4. where are the ribosomes?
   where does the synthesis of all proteins begin?
   how to export?

Answer 7

1. Facilitate coupling of tRNA anticodons with mRNA codons during protein synthesis
   made of proteins and ribosomal RNA or rRNA
2. has three binding sites for tRNA - - APE
   “add”—-“peptide”(add to strand)—-“exit”
3. Many ribosomes in a chain can translate 1 mRNA at once
   - increase effeciency
4. ribosomes are free in cytosol or bound to ER
   all protein synthesis begins of free ribosomes
   Export proteins signalled to ER by signal recognition particle (srp)

Question 8

steps of TRANSLATON

not transcription

Answer 8

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1. Initiation: Start codon makes mRNA attach to the ribosome, rRNA

2. Elongation: IN THE 5’ TO 3’ DIRECTION
   anti codons from tRNA attach to codons from mRNA which have amino acids on them and then peptide bonds form. FORMS THE POLYPEPTIDE CHAIN
3. Termination: a stop codon is reached and then a release factor(water) is attached to a codon like tRNA
   new polypeptide is ready for processing

Question 9

after TRANSLATION, what must occur

Answer 9

Possible changes: to activate or store the polypeptide

Enzyme may be cleaved (eg. Insulin) cut to activate
Sugars or lipids may be attached
Removal of lead amino acids

Question 10

once a polypeptide is being produced by rRNA, what attaches to it and what happens

Answer 10

SRP attaches to it, makes it bind to ER

and polypeptide is produced and pushed into ER and mRNA goes elsewhere

Question 11

mutations in transcription and translation

3 types

framshift

Answer 11

One wrong nucleotide – one wrong amino
acid – dysfunctional protein

Substitutions, only one is right or wrong
insertions or deletions, everything else down the line is wrong
Produce nonsense or mutation

no effect
missense- A instead of G
nonsense-code for stop

missing amino acid or nucleotide, causes change down the line