Ribosomes + ER Flashcards
Which of the statements about ribosomes in false?
They contain DNA and protein!
What happens to DNA, mRNA then protein?
DNA is replicated, transcribed into mRNA, then mRNA is translated into protein!
Where are the majority of rRNAs synthesised?
Which rRNA is the exception?
Nucleolus!
5S - still made in nucleus though!
The nucleolus is where…
Ribosomal rRNA is made
The GENES coding for the majority of rRNA are found…
Clustered on SPECIFIC chromosomes
The nucleolar organisers are…
Chromosomal regions around which the nucleolus forms!
Which processes contribute to the production of MATURE 28S rRNA?
RNA Cleavage
Transcription
Chemical Modification
Where are ribosomal subunit ASSEMBLED?
Nucleolus!
Where are ribosomal PROTEINS TRANSLATED?
Cytoplasm!
Where are BOTH subunits assembled (complete!)?
Cytoplasm - ONLY when encounter mRNA
Where are ribosomal PROTEINS transcribed?
Nucleus
Majority of rRNAs are produced in… from multiple… found on… chromosomes. Regions containing these clusters are known as…
Nucleolus
Genes
10
Nucleolar organisers!
The three MATURE RNAs are:
28S
18S
5.8S
Which subunit contains the mRNA binding groove?
Small!
Which part of ribosome does incoming AA acyl-tRNA first interact?
The A- site
In what direction is mRNA read during translation?
5 to 3
In what direction are proteins synthesised?
N TO C
What is catalytic RNA called?
Eg?
Ribozyme
28S rRNA
The start codon is… and encodes for the AA…
AUG
Methionine
How many stop codons does the STANDARD Eukaryotic genetic code contain?
3 - UAG, UAA and UGA
What is the name of the Eukaryotic degradation machinery?
What’s it’s structure?
What allows selective access into this structure?
Proteasome
Hollow tube
Caps!
Name 2 types of protein synthesised INTO the ER
Secretory and transmembranous
STEP 1 OF TRANSLOCATION OF SECRETORY PROTEIN INTO ER:
The… binds to the… and…
Signal recognition particle
Signal peptide
Pauses translation
STEP 2 OF TRANSLOCATION OF SECRETORY PROTEIN INTO ER:
The… attached to the protein being synthesised interacts with the… and brings the ribosome to the… in the ER membrane.
SRP
Signal recognition receptor
Protein translocator
STEP 3 OF TRANSLOCATION OF SECRETORY PROTEIN INTO ER:
… blocking the… is displaced allowing translation to proceed into the….
The SRP and SRP Receptor are…
PLUG
Protein translocator
ER lumen
Recycled!
Co- translational translocation into the ER lumen requires NO MORE energy than translation in cytoplasm?
True or false?
TRUE
The enzyme that removes signal peptide from soluble secretory protein is…
Why is this necessary?
Signal Peptidase
The hydrophobic signal peptide is RETAINED within the membrane!
Where does the majority of NEW membrane synthesis occur?
The endoplasmic reticulum
Where are the enzymes that synthesise testosterone mainly found?
The SMOOTH ER
Name 2 cell types where the SMOOTH ER is present
Muscle
Testes
Muscle Cells: Sarcoplasmic Reticulum stores… which is released when AP from a nerve… the plasma membrane.
Rise in levels of… in the… tells the muscle to…
Once membrane potential restored and the channel CLOSED, abundant… in the membrane rapidly return these ions to the SR!
Calcium Depolarises Calcium IONS Cytoplasm Contract! PUMPS
What structures + functions do we have to protect our DNA?
Condensation of chromatin
Nuclear envelope with nuclear pores
Requirement of nuclear localisation signal to enter nucleus
Telomeres!
Difference between rRNA and mRNA?
rRNA = ribosomal RNA / mRNA = messenger RNA
rRNA used to create ribosomes!
mRNA used in translation by ribosome as the instructions for which AA come a next!
Relevance of nucleolar organiser?
LOTS of RNA polymerase is in 1 place!
And multiple copies of rRNA genes are brought together
Why do we need multiple copies of genes that generate rRNA?
We need LOTS of rRNAs!!!
What is meant by RNA processing?
What is the point of this?
1 original RNA template from 1 gene is chopped up into 3 rRNAs
Polymerase doesn’t need to find 3 promoters - does it all in one go!
Enables many more polymerase to be on SAME gene = more efficient!
What are the 3 steps of translation?
Codon recognition, peptide bond formation and the release of empty tRNA!
Why are the ribosomes really ribozymes?
Because the H+ group temporarily forms a complex in the 28S rRNA enabling the peptide bond formation to occur more RAPIDLY than it would otherwise!
What has to happen for translation to be initiated?
What causes translation to end?
Small subunit scans mRNA for AUG codon and binds to tRNA-met then recruits the large subunit!
Release factor binding to A site!
What factors control protein concentration within the cell?
Rate of translation
Rate of degradation by the proteasome
How does the proteasome recognise its ‘victims’?
Addition of multiple Ubiquitin molecules but E2/E3 Ubiquitin ligases!
What tag is added to proteins destined to be degraded in the proteasome?
Ubiquitin
What catalyses peptide bond formation in the eukaryotic ribosome?
28S rRNA
A peptide bond…
Joins 2 amino acids together in a protein!
Which of the following types of proteins are synthesised DIRECTLY into the endoplasmic reticulum?
Secretory
The Endoplasmic Reticulum is composed of a … surrounding the space called the …
It is continuous with the …
Phospholipid bilayer
Lumen
Outer nuclear membrane
During Translation , what is the name given to the step where the 3 bases in mRNA pair with the 3 complementary bases in the appropriate tRNA?
Codon recognition / Base pairing
When the amino acid is transferred from the tRNA to the Growing Chain, what reaction takes place?
Peptide bond formation!
The … cells of the testes synthesise… which is a …
This group of signalling molecules are synthesised from… which is made and modified by enzymes housed on the expanded …
Leydig Testosterone Steroid hormone Cholesterol Smooth ER
Which subunit of the ribosome contains the Catalytic Site?
Large - 60S
